History UsefulNotes / StockDinosaursNonDinosaurs

''Hylonomus'', similar to a 1-foot-long lizard, is still today considered the first undisputable reptile, hailing from the Late Carboniferous of Nova Scotia, Canada about 312 mya. ''Hylonomus'' was long considered a parareptilian, but today is mostly classified as a diapsid relative, thus belonging to a different lineage than ''Scutosaurus'' and ''Mesosaurus'' above. It's also famous because many skeletons of it have ben found in hollowed-out petrified stumps: it could have fallen into them and gotten trapped (or drowned if they were full of water). Two competitors for the "first reptile" title popped up in the 1990s. The first, ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Westlothiana]]'' (from the Early Carboniferous of Scotland, 338 mya), seemed to take the record over from ''Hylonomus'' (earning it the nickname "Lizzie" in the media), but is now mostly considered a very reptile-like "amphibian" (sensu lato). The other, ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Casineria]]'' (about the same age as "Lizzie" and also Scottish), is much more heavily contested as its sole, fragmentary fossil shows affinities with amphibians and may in fact represent a transitional form between reptiles and their ancestors.

In ''Series/WalkingWithMonsters'', its close and almost-identical (but slightly older) relative ''Hynerpeton'', found only in 1994 in Pennsylvania, USA, is shown in the traditional mainly-terrestrial way, but also with many unlikely traits typical of ''modern'' true amphibians: like frogs, it's given a loud voice and scale-less skin, and lays eggs that are just the same shape as frogspawn. One individual is killed and eaten by the giant lungfish-like ''Hyneria'' (see ''Eusthenopteron'' in the next folder below for more on that).

The [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures placoderms]] were a group of armored fishes that thrived during the Devonian period, going extinct at its end well before the dinosaurs evolved. Most were small, obscure animals, but the [[{{Pun}} big]] exception is the most infamous of them all -- ''Dunkleosteus'' ("Dunkle's bone"; formerly known as ''Dinichthys'', "terrible fish").

It was evidently the top predator of its time: the Late Devonian, the same period in which the "ur-amphibian" ''Ichthyostega'' lived, and its fossils have been found in North America, Europe, and Africa. Studies of its jaw reveal that it probably sucked up food like a vacuum as many modern fish do, using its tooth-plates to slice through armored prey in less than a second, like a giant guillotine. Since it couldn't chew, it would have had to regularly regurgitate the armor and bones of its prey in the same way owls regurgitate pellets of undigestable bones and fur; indeed, its fossilized vomit is regularly found in Late Devonian fossil beds. Additionally, several ''Dunkleosteus'' fossils preserve evidence of being attacked by other ''Dunkleosteus'', which has led some to suggest that they were active cannibals like many fish today are. It was traditionally thought of a slow creature due to the way it was formerly reconstructed, but we now believe it was a very fast-moving animal that pursued early sharks, ammonites, and other placoderms in the open ocean. Since placoderms are totall extinct, we cannot easily compare ''Dunkleosteus'' with modern fish, but based on on some exquisite specimens of smaller placoderms, it likely gave live birth.

''Xiphactinus'' shares several traits with ''Dunkleosteus''. It was only slightly smaller (6 meters / 18 feet long at most), and much smaller than Megalodon; however, if alive today, it would be one of the largest non-shark, non-ray fish along with the [[http://en.wikipedia.org/wiki/Huso_huso Beluga Sturgeon]] and the [[http://en.wikipedia.org/wiki/Mola_mola Oceanic Sunfish]], both slightly exceeding 1 ton. One of the largest...at least, in mass: the modern deep-sea [[http://en.wikipedia.org/wiki/Regalecus_glesne Giant Oarfish]] can reach 30ft / 10 m or more in length, but is much more slender than ''Xiphactinus'' was, thus less-massive (a bit like giant anacondas that are longer but less-heavy than giant crocodilians today).

Another common trait with ''Dunkleosteus'' is that it was in older media known by another name: "Portheus molossus". ''Xiphactinus audax'' means "courageous sword ray"; the meaning of "''Portheus''" comes from a [[Myth/GreekMythology Greek mythical character]], but ''molossus'' refers to an early breed of mastiff. Indeed, its protruding lower jaw slightly resembles that of a bulldog; this, together with its long-pointed teeth, clearly indicates it was a predator. But unlike ''Dunkleosteus'', it didn't cut the prey into pieces, but swallowed and sucked them whole like most modern bony fish. Indeed it was a primitive [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Teleostean]], the most evolved subgroup of bony fish today, and a distant relative of herrings, tarpons, and arapaimas. It was only larger than them, and thus with a not-at-all exotic appearance compared with many fish of the Paleozoic — not only placoderms like ''Dunkleosteus'' but also acanthodians, early sharks, lobe-finned fish, and the ostracoderms (some of them are below).

Its behavior in life could have been similar to the modern Dorado fish (''[[http://en.wikipedia.org/wiki/Coryphaena Coryphaena]]''), pursuing actively its game, but it's uncertain if it lived in shoals or was solitary. Like large modern actinopterygians/teleosts it arguably had external fertilization and lied a huge number of tiny unshelled eggs (sharks have internal fertilization, their eggs have a keratinous "shell" and are bigger and less-numerous).

In documentary media, ''Xiphactinus'' or "''Portheus''" is typically portrayed as an underdog predator, which gulps big items like the swimming bird ''Hesperornis'' but in turn falls victim to the dominant marine reptiles of the Cretaceous (especially large mosasaurs like ''Tylosaurus''). ''Series/SeaMonsters'' oversized it a bit, and showed it as one of the dangers in the most perilous sea of prehistory (nicknamed [[{{Demonization}} Hell's Aquarium]] by Nigel Marven in the program). Obviously, in mainstream media it's largely ignored as is usual for the ray-finned fish (actinopterygians) of the past (''Lepidotes'', ''Leedsichthys'', etc.) because of its "generic fish" look compared with other giant sea-dwellers of the past like reptiles, cetaceans, giant sharks, cephalopods, etc.

This animal is classically mentioned in paleo-books coupled with ''Ichthyostega'', to show how vertebrates came onto land for the first time. The long-named ''Eusthenopteron'' means "strong fin". Its shape recalled a bit that of the famous ur-amphibian above, but smaller (60cm), with fleshy paired fins instead of true legs, classically fishy dorsal and anal fins, and a curious three-lobed caudal fin reminiscent of [[Myth/GreekMythology Poseidon]]'s trident. Like typical paleoamphibians it had even labyrinthic teeth, underlining its affinity with them. Its lifestyle was probably similar to a lungfish's, and like a lungfish was probably also able to breath air with primitive lungs and occasionally crawl out of the water to escape drought. Like lungfish its fry very probably underwent metamorphosis, but unlike them, the adults were scaly like a coelacanth (the other living fish similar to the eusthenopteron). ''Eusthenopteron'' appears in WesternAnimation/{{Fantasia}}.

Its almost-identical relative ''[[http://en.wikipedia.org/wiki/Hyneria Hyneria]]'' was much bigger (3-4m long), and [[BiggerIsBetter because of its size]] was chosen by ''Series/WalkingWithMonsters'' producers instead of ''Eusthenopteron'' as the representative of Sarcopterygians, aka the "lobe-finned fish" (and, of course, was scaled up still further, and was given even a human look with big forward eyes). However, it's shown only to provide a predator to the ''Ichthyostega'' relative ''Hynerpeton'', and with no mention at all of its role as one of the forerunners of land vertebrates: in effect it was eating its descendant!

''Cephalaspis'' and ''Pteraspis'' are perhaps the two most-depicted Ostracoderms in paleo-media — at least, non-fictional media. As ostracoderms, they were small critters similar to strange modern bony fish at a glance; actually, they were more similar to the so-called "jawless fish" like the modern lamprey and hagfish, and likewise lacked jaws. Unlike the latter, they had armored heads and bodies, which made them look more like the aforementioned placoderms such as ''Dunkleosteus''.

But unlike ''Dunkleosteus'', ''Cephalaspis'' and ''Pteraspis'' were totally harmless creatures, and much, much smaller: some ''Pteraspis'' were no longer than a human finger. They were also very different from lampreys and hagfish, being inoffensive filter-feeders or bottom-feeders of tiny food items, not parasites or scavengers of large animals like the as-yet nonexistent giant bony fish or cetaceans.

These two ostracoderms lived from the Silurian to the Devonian, in the middle of the Paleozoic. ''Series/WalkingWithMonsters'' chose to show ''Cephalaspis'' as the prototypical ostracoderm, as [[RedShirt fodder]] for giant "scorpions" and as a salmon-like migrator, but this last behavior is only speculative — and rather unlikely, since they were probably slower swimmers compared with most modern fish. But it's always RuleOfCool that wins...

Temnospondyls first appeared in the Early Carboniferous, and proceeded to dominate the world's waterways from the Late Carboniferous to the Early Triassic, occupying the same niche held by crocodiles today. Some became more land-dwelling (although still bound by the need to lay their eggs in water), and others even managed to enter the ocean (all living amphibians are all freshwater-bound or terrestrial and cannot survive in saltwater). But in the Middle and Late Triassic, they entered a sharp decline as they were outcompeted the ancestors of crocodilians. The last species ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Koolasuchus]]'' of ''Series/WalkingWithDinosaurs'' fame managed to reach the Early Cretaceous only because of its isolation in Australia, which at the time was in the Antarctic circle and thus too cold for crocs. ''However'', it seems the temnospondyls may not be as extinct as we thought, as new research suggests the modern-day lissamphibians (frogs, toads, newts, salamanders, etc.) may in fact be the sole surviving descendants of these giants.

It's usually accepted that the biggest/most spectacular prehistoric animals lived in the Age of Reptiles, the mythical Mesozoic. Well, sharks give us a notable exception. The biggest known predatory shark ever lived ''just a few million years ago'', at the time of the first hominids!

[[RuleOfCool Obviously]], this animal is often shown in documentary media: for example, its open jaws are often depicted with [[ThreateningShark some people inside]] to show how immense they are. Recently, this animal has fascinated the world of fiction, to the point that megalodon has become a trope on its own. But wait: ''Megalodon'' (literally "big tooth") is ''not'' the name of its genus; it's that of its species. The full scientific name used to be ''Carcharodon megalodon''; today it's ''Carcharocles megalodon''. It was believed to have been an extremely close relative of the great white shark (''Carcharodon carcharias''); today it's placed in a different family convergently similar to the great white's, but still in the same order of true sharks: the [[http://en.wikipedia.org/wiki/Lamniformes Lamniformes]], which also include the long-tailed thresher sharks, the filter-feeding basking shark, the deep-sea megamouth shark, and the toothy-grinned sandtiger sharks, among the others.

Like the most impressive extinct beasts, Megalodon is often a victim of sensationalism. Some sources describe it as 30m/90ft long, nearly as big as a blue whale; palaeontologists estimate it at just over a third to just under two thirds of this length. Still, it remains one of the biggest known fishes of all times as well as the biggest known predatory shark, and one of the most successful apex predators ever, with a tenure of 20 million years. Only ''Livyatan'', a whale related to the modern sperm whales, was true rival, being its contemporary in the same seas.

Like this predatory whale, Megalodon may have been a specialist hunter of large cetaceans, and its bite marks have been found in whale skeletons, but it could also have fed on smaller prey. We don't know what colors it was, but was arguably countershaded, like typical big swimming sea creatures. If it was solitary or lived in groups is uncertain. Its reproductive methods are also matter of discussion. As typical of prehistoric sharks, its most common fossil remains are jaws and teeth, not the softer cartilaginous rest of its skeleton.

We don't know why it went extinct; possibly because of climatic changes that deprived it (and its mammalian rival) of its main food sources: in particular the closing of the Central American Seaway, which was an important hunting and migration area. It is hypothesized that Megalodon held back the [[UsefulNotes/PrehistoricLifeMammals evolution of cetaceans themselves]], which underwent a third explosion in diversity right after its extinction — therefore, the theory that orcas outcompeted the giant shark is highly unlikely.

Megalodon is probably the one prehistoric creature that gets almost as much sensationalism as ''Tyrannosaurus rex'': from frequent, fraudulent reports of it still patrolling the seas to erroneous portrayals of it chomping on Mesozoic marine reptiles (despite not appearing until ''long'' after those creatures had gone extinct), Megalodon is frequently cast as the ultimate sea predator. This obviously cannot be verified — in the ''Franchise/WalkingWith'' spinoff ''Sea Monsters'' it's portrayed as "only" the third-most-dangerous marine superpredator of Prehistory, after the sea reptiles ''Tylosaurus'' and ''Liopleurodon'', but before the fish below. The character "Meg" is an example of ALizardNamedLiz, as is clearly the initial of Megalodon.

Most [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures placoderms]], armored fishes that went extinct well before the dinosaurs evolved, were small. The [[{{Pun}} big]] exception is ''Dunkleosteus''.

19ft / 6.5m long, the size of a great white shark (some sources have upsized it to 30ft / 10m), it was only outmatched by its larger but gentler cousin ''[[http://en.wikipedia.org/wiki/Titanichthys Titanichthys]]'' ("titanic fish") and an obscure chimera known as ''Parahelicoprion'' for the title of largest animal in the Paleozoic era, the geological era before the Mesozoic. It was the same shape as the smaller and lesser-known ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Coccosteus]]'', with the same kind of armored head and the same strange scissor-like "teeth", actually plates of sharpened bone.

It was evidently the top predator of its time: the Devonian, the same period in which the "ur-amphibian" ''Ichthyostega'' lived, and was able to chop up even the toughest prey. Studies of its jaw reveal that it probably sucked up food like a vacuum like many modern fish do, using its bone tooth-like plates to slice prey into chunks like scissors, with a bite force of 4400 pounds — possibly the strongest bite of any animal that ever lived. Its fossilized vomit has been found too, indicating that it often regurgitated the armour and bones of its prey, like what some modern animals do (see those birds like owls or shorebirds that regurgitate pellets of undigested food). Also of interest is that several ''Dunkleosteus'' fossils preserve evidence of being attacked by other ''Dunkleosteus'', which has led some to suggest that they were active cannibals like modern pikes or other fish.

In older sources it's referred to as ''[[http://en.wikipedia.org/wiki/Dinichthys Dinichthys]]'' ("terrible fish", which, however, may be a separate animal); the much less awesome name ''Dunkleosteus'' means "Dunkle's bone" after a museum curator. Belonging to a totally-extinct group of fish, we cannot easily compare it with modern fish: for example, we don't know how it mated, or what shape and number its eggs were, nor if parental care was present.

Despite its status as "the living tank fish", ''Dunkleosteus'' has not gained much attention outside of paleo books; in ''Franchise/WalkingWith'' it appears as one of the "[[PrehistoricMonster monsters]]" encountered by Nigel Marven while time-traveling, and to better fit the role is portrayed as [[RuleOfScary excessively scary]], with cat eyes and blood-red coloration, while most other portrayals show it with round pupils like a typical fish, and more generic colors. Here, it's the fifth-most-dangerous superpredator of all time, after two marine reptiles, Megalodon, and the early whale ''Basilosaurus''.

# '''Entry Time:''' 1956
# '''TropeMaker:''' Documentary and book media

Extinct amphibians are interesting, and the stock ones are from ''before'' the dinosaurs (though, of course, authors frequently forget that and put them in dinosaur settings anyway).

''Ichthyostega'' has always been one of the most iconic paleo-amphibians. Found in Greenland — HilariousInHindsight, during most the prehistory Greenland really ''was'' a green land, covered with forests; the ice cap formed only 30 million years ago in the Cenozoic — ''Ichthyostega'' lived before all the animals mentioned above, in the Devonian Period, about 350 mya, in a time when flying insects didn't yet exist and the very first forests had just started to grow.

Found at the start of the XX century, it was considered the very first land vertebrate for all the century in question, and the common ancestor of all tetrapods (mammals + birds + reptiles + amphibians). Like ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Archaeopteryx]]'', ''Ichthyostega'' has been often cited as a "missing link" between two main animal classes: fish and amphibians in this case, and like the "ur-bird" and the "ur-mammals" (the therapsids), portrayed as an icon of Evolution. However, since the 1990s new intermediate forms between fish and land animals have been found; ''Acanthostega'' and ''Tiktaalik'' are two relatively known examples, see the [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Fish section]].

Like many other basal tetrapods ''Ichthyostega'' was a big animal, 5ft / 1.5 m long and weighing as much as an adult human. This half-fish/half-amphibian, often quoted as a "fish with legs" or an "amphibian with fin", was indeed one of the first animals that developed true legs, already similar to modern animals except for one thing: it had ''seven'' digits on each foot - later vertebrates have no more than five, except for very rare anomalies like some ichthyosaurs. Its body plan, however, had still several fishy traits (''Ichthyostega'' indeed means "roof fish"): a streamlined body, fish-like scales, a powerful tail with a long true ''fin'' on top, and maybe even a "lateral line" to sense underwater! On the other hand, it could have had eyelids and external ears like in modern amphibians, other than two breathing lungs in the adults. The larval stage is unknown, but was certainly made of "tadpole"-like gilled small creatures that hatched in water and then underwent a metamorphosis like in modern amphibians, but also in modern lungfish.

But wait: though classical portrayals show it crawling on dry land, today scientists think ''Ichthyostega'' lived mainly in water, and [[ScienceMarchesOn recently research]] suggest its limbs were ''not'' used for walking on dry soil but only on the bottom of lakes and rivers, like a modern alligator-salamander of North America or a Giant Japanese Salamander (the biggest living amphibian today, incidentally the same size of ''Ichthyostega'').

In ''Series/WalkingWithMonsters'', its close and almost-identical relative ''Hynerpeton'', found only in the 2000s, is shown in the traditional mainly-terrestrial way, but also with many unlikely traits typical of ''modern'' amphibians: like frogs, it's given a loud voice and scale-less skin, and lays eggs that are just the same shape as frog, toad, or newt eggs. One individual is finally captured by one of its ancestors, the giant lungfish-like ''Hyneria'' (see below).

''Diplocaulus'' was two feet / 60 cm long, much smaller than ''Ichthyostega'' (but still bigger than most modern salamanders) and lived in Early Permian North America contemporary with the famous hyperpredatory synapsid ''Dimetrodon''. Its unique boomerang-like head makes it a very bizarre-looking and enigmatic prehistoric animal, and a very common sight in paleo books (though it has not yet appeared in ''Series/WalkingWithMonsters'' or other CGI documentaries). The purpose of its head protrusions has been a headache to paleontologists: a swimming device? A display tool? A mean to excavate the bottom of lakes? Some have even suggested the shape of the head prevented ''Diplocaulus'' from being swallowed by larger amphibians such as ''Eryops'' (below)!

''Diplocaulus'' means "double-stem" — while ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Diplodocus]]'' means "double-beam". Despite its appearance, was not a member of the group comprising modern amphibians (the Lissamphibians): it was a Lepospondylian, a Carboniferous/Permian group whose shape only coincidentally recalled that of modern salamanders and newts. Its eyes and nostrils were placed on the top of its flattened head, and were very close to each other (the exact opposite of a modern hammerhead shark, whose eyes and nostrils are at the extremities of the "hammer"), which gave it what may have been a rather funny appearance if seen from above.

According to experts it was mainly aquatic, probably swimming with its tail and/or walking on the bottom of the water bodies with its five-toed feet. ''Diplocaulus'' arguably fed upon small water critters, and could have fallen prey to larger fish, amphibians, and perhaps also the ''Dimetrodon'' when on land, being arguably as slow as a big modern salamander on dry soil. In water, on the other hand, it could have been more fast and agile. We don't know what shape its larvae were, belonging to a totally extinct group of paleoamphibians; it could have had a lateral line like fish to hear vibrations underwater, because some modern lissamphibians that live in water even when adults do have it.

Temnospondyli (lit. "cut vertebrae") were the most successful paleo-amphibians in RealLife, thriving from the Late Carboniferous to the Late Triassic, with one holdout reaching the Cretaceous. The most iconic of them has traditionally been ''Eryops megacephalus'' ("big-headed drawn-out face").

2.4m/8ft long, bigger than ''Ichthyostega'', and weighing as much as two adult humans, this short-named amphibian was the size of a small crocodile, and has indeed classically been compared with crocs in documentary media. But ''Eryops'' was more massively-built than a modern-day crocodilian; it had a shorter tail, lacked armor on its back, and its limbs were comparatively weaker, making it probably more awkward than a croc on land. Still, it had a very alligator-like head, with eyes placed above the skull and a large snout. Its teeth were different from those of a gator, though, being thinner and more numerous, more like a gharial's.

Living in North American Early Permian, ''Eryops'' is believed by most experts to have been mainly aquatic — other contemporaneous relatives, such as the equally short-named armored ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Cacops]]'' and the sail-backed ''Edaphosaurus''-like ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Platyhystrix]]'', were more terrestrial. ''Eryops'' was arguably a predator of other smaller paleo-amphibians such as ''Diplocaulus'' above and also fish and invertebrates, but when on dry land it could have fallen prey to the bigger species of ''Dimetrodon''. Nonetheless, it can't be ruled out that it could have raided ''Dimetrodon'' and ''Edaphosaurus'' nests and hatchlings if it got the chance. Like other extinct amphibians, ''Eryops'' can be wrongly portrayed with reptilian scales and reptilian nails in illustrations: these features, however, are typical of the Amniotes.

From the Early Triassic Period comes the even larger ''Mastodonsaurus''. Its name means "mastodon lizard" for its size, and sometimes is misspelled "Mastodontosaurus". It was one of the very first giant amphibians discovered to science, in the first half of the 1800s, and portrayed in the London Crystal Palace Park as "Labyrinthodon". It was the namesake of the Labyrinthodonts ("labyrinth teeth"), the catch-all name for non-frog, non-salamander and non-caecilian extinct amphibians — so-named because many had teeth with strange convoluted "labyrinthic" patterns of enamel inside them for uncertain purpose. Interesting that in the Triassic also existed ''marine'' temnospondylian amphibians, like ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Aphaneramma]]'', while living amphibians are all freshwater-living and/or terrestrial and never go to the open seas.

''Mastodonsaurus'' lived in Europe before the first dinosaurs like ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Plateosaurus]]'' or the North American ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Coelophysis]]''. 15ft / 5m long, it was long considered the biggest amphibian ever, but this title was later taken by the 8 m long but more slender ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Prionosuchus]]''. Nonetheless, ''Mastodonsaurus'' remains remarkable for its massive body, powerful limbs, and its 1.2m/4ft-long head with a couple of strange protruding teeth in the lower jaw, which may have perforated the upper jaw in life (though this latest detail is usually ignored in paleo-books). During the Triassic, giant amphibians like this became rarer and rarer, becoming outcompeted by the ancestors of crocodilians. The temnospondyl ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Koolasuchus]]'' managed to reach Early Cretaceous only because of its isolation in Australia, a landmass long devoid of paleocrocs.

Reptiliomorphs ("reptile-shaped") were transitional animals between amphibians and the first Amniotes (reptiles, birds and mammals). We don't know if they already had scaly skin like reptiles, or not, like amphibians today. Traditionally the best-known among these half-amphibian/half-reptiles has been ''Seymouria baylorensis''. The genus name comes from the town of Seymour, Texas, near where it was discovered; the species name from Baylor County.

''Seymouria'' used to be described in textbooks as the "missing link" between reptiles and amphibians, or alternatively the very first reptile. In the latter case, it was considered a "cotylosaur" (the catch-all name for the earliest reptiles). Only 60cm long, like ''Diplocaulus'', it lived in Early Permian North America alongside the "hammerhead amphibian" and ''Eryops''. It was more terrestrial than them, though, and had a greater chance of meeting ''Dimetrodon'' in RealLife; it was possibly one of its most frequent prey. In ''Series/WalkingWithMonsters'', however, it's shown mainly as a potential thief of the latter's eggs. Despite its similarity to reptiles, ''Seymouria'' still laid shell-less eggs from which "tadpoles" hatched in water, as some fossils show. Technically, tadpoles are only the larvae of frogs and toads, the ''Anura'' (meaning tail-less in Greek). Prehistoric frogs are rarely-seen in Fictionland, but when they do, they normally don't belong to specific kinds of frogs or toads; for example, the "tailed frog" that jumps near Littlefoot in ''The Land Before Time'' film is an invention of the movie, though ancestral frogs really existed at dinosaurs' time, some very similar to the modern ones.

When we think North American wildlife, we tend to think stuff like bears, bison, deer, wolves, and cougars. So it comes as a surprise to many to learn that camels (and their South American relatives, the llamas and alpacas; together, they form the family Camelidae) were once considered characteristic of North American fauna. Indeed, camels and llamas ''evolved'' in North America and were ''only'' found on that continent until relatively recently when the ancestors of today's dromedaries and Bactrians (both in the genus ''Camelus'') crossed over the Bering land bridge into Asia and the ancestors of llamas and alpacas (genus ''Lama'') entered South America across the newborn Isthmus of Panama.

We often think of Ice Age animals as primordial beasts of a bygone era, but the truth is that they were all very modern animals adapted to today's world; virtually all living and historically-extinct animals we know of co-existed with them, including us humans, and in another timeline, the Pleistocene megafauna would still be roaming Earth today. In the case of Australia's ancient giants -- the marsupial lion, the diprotodont, the giant short-faced kangaroo, Megalania, and others -- it seems they all met an untimely end at the hands of the first Aboriginals, who set fires to grow different plant species, consequently starving their prey into extinction. The introduction of the dingo a few centuries later spelled the same fate for the other main mammalian predators of prehistoric Australia -- the smaller thylacines (''Thylacinus cynocephalus''; see Historically-Extinct Mammals) and Tasmanian devils. While the devils still survive today, the thylacine missed the chance to be observed by modern wildlife lovers only by a matter of decades. Forget {{Prehistoric Monster}}s, it seems that HumansAreTheRealMonsters.

Oh, and all the animals above were not only the horse's ancestors, but also the donkey's and zebra's. Despite their different appearances and habits, modern equids are so closely related to each other they're all placed in a single genus, ''Equus'' -- by comparison, the modern five rhinoceros species are put in ''four'' different genera: ''Diceros'' (the black rhino), ''Ceratotherium'' (the white rhino), ''Dicerorhinus'' (the Sumatran rhino), and the namesake ''Rhinoceros'' (the Indian and Javan rhinos). The genus ''Equus'' also includes many Ice Age species and two recent historical extinctions: the African quagga, a kind of zebra with incomplete stripes, and the European tarpan, the direct ancestor of the domestic horse.

''Arsinoitherium'' means "Arsinoe's beast": Arsinoe was an {{Ancient Egypt}}ian queen. It is sometimes misspelled "Arsinotherium" without the "i" in the middle because so it's [[TheUnpronounceable easier to pronounce]]. ''Arsinoitherium'' lived in Africa during the Late Eocene and Early Oligocene, after ''Uintatherium'' but contemporaneous with the North American brontotheres, and was of similar size and body shape to the former. Its classification has long been an enigma, but today, it is considered one of the [[http://en.wikipedia.org/wiki/Afrotheria afrotheres]], making it a cousin of elephants, sea-cows, hyraxes, and the aardvark. Specifically, it belongs to extinct subgroup known as the embrithopods, being the last and largest of this poorly-known lineage.

''Amphicyon'' means "half-dog", an apt term because it was related to canines but was not one of them -- it's the namesake of its own family of caniform carnivores, the amphicyonids, or "bear-dogs". ''Amphicyon'' was rather in the middle between [[MixAndMatchCritter a long-tailed wolf and a slender bear]], possessing the flat-footed, or plantigrade, posture of the latter (dogs walk on their toes, in a digitigrade posture). Over two dozen species of ''Amphicyon'' are known across Miocene Europe, Asia, and North America, but the most infamous is the massive ''A. ingens'', the apex predator of Middle Miocene North America. Bear-dogs were widespread across the three abovementioned continents and Africa from the Middle Eocene to Late Miocene, but the cause of their extinction is currently unknown. They should not be confused with [[https://en.wikipedia.org/wiki/Hemicyoninae the "dog-bears", or hemicyonines,]] a Miocene subfamily of bears that evolved towards being fast-running pursuit predators.

Carnivorous ungulate-relatives are strange enough already, but few groups of extinct mammals have baffled scientists as much as the demostylians, the only totally extinct group of sea mammals ever. Debate rages over which modern mammal group this lineage of ''true'' sea mammals is most closely related to -- they are traditionally believed to be afrotheres related to sea-cows and elephants, but the fact they are exclusively from the North Pacific contradicts the consistently African and Atlantic evolutionary history of the afrotheres, leading other scientists to propose they are instead perissodactyls or perissodactyl-relatives, closer to horses and rhinos. However, the jury remains out for now. Desmostylians looked a bit like hippos but with shorter hindlimbs than forelimbs and smaller heads. Also like hippos, they had small tusk-like incisors and canines, except these pointed forward and there were multiple on each jaw. They also possessed uniquely tubercled cheek teeth they used to eat kelp. They were once thought to be amphibious, but later studies suggest they were unable to support their weight on land and thus fully aquatic, mostly power-walking on the bottom like hippos do.

''Desmostylus'' ("bundle-pillar", for the shape of its teeth) is the archetype and the most known of the group, first found by Marsh in USA during the Bone Wars; it lived in shallow coastal seas from Japan to Baja Califonia up to Alaska and Siberia during the Miocene. As a group, the demostylians lasted throughout the Oligocene and Miocene, going extinct as sea-cows rose to prominence and entered the North Pacific (where they also eventually went extinct during historical times). Interestingly, the demostylians are very popular in Japan, where they are among the most well-known groups of prehistoric mammals, due to the many fossils of them found there.

''Livyatan'' was not the only one of its kind. Throughout the Miocene lived similar sperm whale-relatives of smaller size and with smaller (but still huge) teeth: their scientific names recall the one of the modern sperm whale, ''Physeter'', with a prefix ahead. Among the most notorious of these are the 15ft-long ''Acrophyseter'' from Middle Miocene Peru, the 23ft-long ''Brygmophyseter'' from Middle Miocene Japan (portrayed in ''Series/JurassicFightClub'' as the rival of Megalodon), and the 23ft-long ''Zygophyseter'' from Late Miocene Italy; ''Acrophyseter'' and ''Zygophyseter'' stand out for having smaller spermaceti organs than the others, giving them a dolphin-like beak. Together with ''Livyatan'' are nicknamed "macroraptorial sperm whales" (not considered an actual taxonomic group within Physeteroidea). These animals were all apex predators that occupied the same niche as the modern orca; they certainly would have given Megalodon a run for its money as King of the Cenozoic Ocean!

This animal is not strictly prehistoric, but like the [[UsefulNotes/StockDinosaursSaurischianDinosaurs Dodo bird]], went extinct in the Modern Era thanks to humans.

The aurochs (whose scientific name, ''Bos primigenius'', means "primeval ox") was, together with the [[http://en.wikipedia.org/wiki/Bison_bonasus wisent]] (European bison), the biggest European land mammal to survive the Ice Ages and reach recorded history. It's a classic imprecision in media to say the aurochs was a ''prehistoric'' animal; this is not completely wrong, since it was widespread during the Ice Ages both in Europe and in Asia alongside woolly mammoths, woolly rhinos, cave bears and so on, but strictly "prehistoric" creatures are those that disappeared before the dawn of civilization (roughly 4000 B.C.).

Also known as the urus or the ure, the aurochs was a powerful animal, though sometimes oversized in media: it was actually no bigger than modern wild bovines. According to paintings, the aurochs' color varied from brown to blackish but usually darker than the wisent, its fur was quite long to withstand frigid winters but shorter than a Tibetan yak, and its body was without the typical hump on the shoulders of a true bison. It roamed ancient forests and steppes, and was probably a browser/grazer like the wisent. Its predators would have included cave lions, cave hyenas, modern wolves and brown bears, from which it defended itself with its long robust pointy horns and rapid charges — it was a fast runner despite its weight of one ton. It gave birth to one calf at a time after a long gestation of 10-11 months, and like all modern ruminants it chewed its cud to better digest plant matter.

The aurochs was already known by prehistoric European people, the Neanderthals and the Cro-Magnons (aka the first European ''Homo sapiens''), who often depicted it in cave art — Lascaux in France and Altamira in Spain, for example — together with many other extinct and extant animals they hunted. Ancient Celtic, Greek, Roman and Medieval peoples too knew the animal, often mentioning it in literature as a particularly dangerous wild game, or as a symbol of power, or (in the case of the Celts) even as a divinity. Some peoples painted images of it on their war shields. The aurochs still appears in the national flag of the modern Republic of Moldova (in Europe).

But since Medieval and Renaissance times, reduction of the forests/steppes it lived in, coupled with extensive hunting, made the aurochs rarer and rarer, until it disappeared entirely in the 17th century together with another large European animal, the tarpan horse (see below). The European bison managed to escape the same fate only thanks to a bunch of individuals saved JustInTime in one small forest between Poland and Belarus, in the 1800s: Bialowieza.

The aurochs left an extremely crucial legacy in modern times, however: around the end of the Ice Age, 10,000 years ago, some aurochs (yes, ''not'' aurochses or aurochsen) were domesticated by humans. This domestication was one of the most successful and important ever: their descendants became the bulls, oxen, and cows (''Bos taurus''), whose contribution to mankind's development, as everyone knows, has been fundamental.

Interestingly, there are very archaic cattle breeds that strongly resemble the aurochs, for example the famous Spanish Fighting Bull used in bullfighting, and some breeds have been reintroduced in ancient European forests (ex. Bialowieza between Poland and Belarus, the same place that saved the last European bison) — resurrecting, at least partially, the memory of the ancient presence in Europe of their wild ancestor.

The tarpan was a true wild horse (''Equus ferus'': "ferus" = wild, "Equus" = horse in Latin) that lived in Europe until the Modern Age, but was depleted by humans along with the aurochs — however, some archaic domestic horse breeds resemble the tarpan, and are visible in some European parks, just like cattle breeds that resemble their own wild ancestor.

The tarpan was a smallish, greyish horse very similar to the living conspecific Przewalski's horse (see below) and the equally rare wild asses of Asia and Africa: all of them combined a donkey-like mane with normal horsy tail. Its behavior was no different from modern wild equids, roaming grasslands and steppes in large herds to defend itself from predators. Less known is another kind of horse, extinct only a bit before human history, ''[[http://en.wikipedia.org/wiki/Equus_giganteus Equus giganteus]]'' ("giant horse"), which is the biggest-known wild equid of all times - only some domestic draft-horses equal it in bulk.

The tarpan too was depicted in prehistoric caves like the aurochs, and mentioned in classic European literature throughout the centuries as "the wild horse". Both the aurochs and the tarpan arguably shared the same voice (mooing and neighing respectively) as their domestic descendants, and both had a quite long gestation of 10-11 months, but the tarpan being an odd-toed ungulate didn't ruminate, like modern equines and unlike bovines.

Among historically-extinct land mammals of Europe there is also the [[http://en.wikipedia.org/wiki/Prolagus_sardus Mediterranean pika]] (''Prolagus sardus''), a short-eared relative of rabbits and hares that lived in the Mediterranean islands of Sardinia and Corsica. In the West Indies (Cuba, Hispaniola, etc.) the [[http://en.wikipedia.org/wiki/Heptaxodontidae Giant hutias]] survived until recorded history: they were cavy-like rodents, and some of them reached 100 kg of weight.

All modern equines are so similar to each other in anatomy that they are all included in a single genus: ''Equus''. This genus, as mentioned in the "horse ancestors" chapter, originated on the North American prairies during the Pleistocene (the Ice Age), and then spread throughout Eurasia toward the [[http://en.wikipedia.org/wiki/Beringia Bering strait]], and later to Africa through the Sinai passage. Modern "wild" (or rather, feral) horses of North America, Asia, Australia etc. actually descend from domestic horses returned to the wild — except for the Mongolian [[http://en.wikipedia.org/wiki/Equus_przewalskii Przewalski's horse]] (another subspecies of ''Equus ferus'', the original wild horse), probably extinct in nature but still surviving in few zoos and parks.

The quagga (''Equus quagga'') was an unusual-looking kind of zebra with dark & white stripes only in the front part of its body, and the remaining body colored uniformly brownish or whitish like [[ZebrasAreJustStripedHorses many horses]]. It was closely related to the modern plains zebra, to the point they may even be the same species, but unlike the latter it lived only in the southernmost part of Africa - making it the southernmost kind of modern equine together with the once critically-endangered [[http:/en.wikipedia.org/wiki/Mountain_zebra Mountain Zebra]].

The quagga's lifestyle was probably identical or very similar to the surviving zebras, but sadly, it was overhunted by European settlers in recent centuries together with some kinds of South African antelopes it shared the land with, notably the [[http://en.wikipedia.org/wiki/Bluebuck Bluebuck]]. Being less skittish and more robust than other zebra species, the quagga was probably well-suited for domestication, making it all the more wasteful that it was instead hunted to extinction.

The quagga is mentioned in the first ''Franchise/JurassicPark'' book as an example of a recently-extinct species of animal that could possibly be cloned in the park, and is still present in several tales of South African people today. It's also one of the several species subject of the [[http://en.wikipedia.org/wiki/De-extinction De-Extinction]] programs to possibly rebirth to life recently-extinct animals.

The story of this mammal is a particular TearJerker. The Steller's sea cow (''Hydrodamalis gigas'', also ''"Rytina gigas"'' in older systematics) was not a cow, despite the name, but a giant relative of modern manatees and dugongs — that is, a large Sirenian, and not a cetacean at all but a distant relative of elephants.

9m long and weighing as much as a large African elephant, and much more than a male elephant-seal, a bull walrus, or a true manatee (genus ''[[http://en.wikipedia.org/wiki/Trichechus Trichechus]]''), it was similar to the latest one in shape but with smaller head and flippers, rougher hide, and the same whale-like fluke as a dugong (genus ''[[http://en.wikipedia.org/wiki/Dugong Dugong]]''), which it was more closely-related to. It used to swim slowly and peacefully in the cold waters of the Northern Pacific coasts along with sea otters and sea lions, grazing kelp and seaweed with its unusual toothless jaws (manatees and dugongs have few teeth). Like modern manatees and dugongs, it gave birth to one offspring at a time after a long gestation, and thus was not an especially fast breeder.

When the first European settlers, among them the researcher Georg Steller (who first described it, hence the common name of the animal) arrived at Wrangler Island and the nearby seas in the 1700s, they first reported its existence to the Western world, finding that the sea cow was already rare at that time, with only ''few thousand'' individuals left. Unfortunately, hunters and whalers soon saw it as a great source of food and animal grease because of its size, and also noted that it was a relatively easy animal to kill, more so than the bigger and/or faster cetaceans nearby. The result was: the giant sirenian went extinct merely ''27 years after its discovery'' — while most other historically-extinct mammals and birds were depleted at least one century after Western people learned about them.

Today, the most endangered sea mammals include animals much smaller than the Steller's sea cow, but still large compared with many modern threatened land mammals: among them, the Chinese river dolphin or Baiji (''[[http://en.wikipedia.org/wiki/Baiji Lipotes vexillifer]]''), maybe extinct during the TurnOfTheMillennium; the small Californian porpoise or Vaquita (''[[http://en.wikipedia.org/wiki/Vaquita Phocoena sinus]]''); and the large Mediterranean and Hawaiian "[[http://en.wikipedia.org/wiki/Monk_seal monk seals]]" (the Caribbean one is already gone). On the other hand, the populations of the biggest living sea-mammal, the worldwide-distributed [[http://en.wikipedia.org/wiki/Blue_whale Blue Whale]], seen now more secure now than they were in the final XX century, when they seemed condemned to an inevitable extinction.

# '''Entry Time:''' Uncertain
# '''TropeMaker:''' Documentary media

This mammal is not strictly prehistoric either, to the point that it could actually [[HesJustHiding still be alive today]]. Nonetheless, like the animals above, it has left several fossils from prehistoric times.

In popular media the thylacine (''Thylacinus cynocephalus'', lit. "[[MixAndMatchCritter pouched dog]] with a [[DogFace dog head]]") is known as the marsupial wolf, the marsupial tiger, the Tasmanian wolf, or the Tasmanian tiger. Wolf, because its shape and size effectively recall that of a long-tailed, round-eared wolf — to the point that it's often cited as an example of convergent evolution with true canids. Tiger, because of its coloration, which was vaguely similar to the [[PantheraAwesome eponymous cat]] but with a simpler design: wide black stripes on the rear of its back upon an otherwise uniformly brownish body.

But this mammal is/was neither a canine, nor a feline; it was of the same systematic group as kangaroos or koalas! More precisely, it was related with smaller still-living carnivorous marsupials of Australia like the Tasmanian "devil" (''Sarcophilus harrisii''), the weasel-like quolls (''Dasyurus''), the ant-eating Numbat (''Myrmecobius fasciatus''), and several mouse-like animals nicknamed "marsupial mice"; while it had nothing to do with the "marsupial lion" and "marsupial sabertooth", see "Ice Age Mammals". It's called Tasmanian because Europeans found it only on the island of Tasmania, but in the past the thylacine also lived on mainland Australia — until it was dethroned by the dingo, an ancient breed of domestic dog brought in the LandDownUnder by the ancestors of Aborigines thousands of years ago.

Like the dodo, the aurochs, the moa, the elephant bird, the great auk, the passenger pigeon, the Steller's sea cow, the quagga, the tarpan, the Haast's eagle, the Carolina parakeet, etc., the thylacine is often and rightly mentioned as an example of Man's irresponsibility. Its possible extinction happened only in the 20th century: [[https://youtu.be/nBpyAOpzlEE old black-and-white films]] exist showing the animal alive in zoos, and reveal that it could open its mouth rather widely. It was hunted to extinction mainly because Tasmanian farmers of the 19th and 20th centuries considered it a serious peril for their livestock, especially their sheep and their poultry. This was only partly true, however, because the animal mainly hunted wild game. The alleged ferocity of the thylacine was notably exaggerated by several reportages and citations in books and encyclopedias as well. These accusations of viciousness and perilousness, even toward humans, were among the excuses that led to it and its placental namesakes, the grey wolf (''Canis lupus'') and the tiger (''Panthera tigris'') being driven to endangerment or extinction from many countries worldwide.

Sometimes, alleged sightings of "[[https://youtu.be/Zs3fSM9UFgs the last thylacine]]" occur in newspapers, but for now none of them is confirmed. Among portrayals in popular media, this animal has made appearances in [[TheEighties 1980s]] anime, wrongly identified as a strange "striped wolf", and as a possible danger for not only livestock but the humans themselves — even though in RealLife there have never been any reports of thylacines attacking humans directly. Like many modern Australian/Oceanian animals it shows up also in the cartoon series ''Tazmania''.

# '''TropeMaker:''' Uncertain, possibly the Wild Mass Guessing about its survival

Other prehistoric mammals with big antler-like things above their heads, like the Pliocene-Pleistocene ''Sivatherium'' of India and Africa and the Miocene ''Synthetoceras'' of North America, were artiodactyls but ''not'' of the deer family: the former a ''giraffe'', the latter a relative of the chevrotain or mouse-deer (not actually a deer); they may nonetheless be wrongly presented as "deer" in pop-media. Of course, none of these real or pseudo-deer were the direct ancestors of any modern deer species.

Other mammals of the Mesozoic are the Early Jurassic ''Morganucodon'' and ''Megazostrodon'' (some of the earliest and most widespread), the beaver-like ''Castorocauda'' and gliding ''Volaticotherium'' of Middle Jurassic China, the Late Jurassic ''Juramaia'' and Early Cretaceous '"Eomaia'' of China (the earliest known placental-ancestors), the digging termite-eater ''Fruitafossor'' of Late Jurassic North America (living alongside ''Allosaurus'', ''Diplodocus'', and ''Stegosaurus''), ''Cronopio'' of Late Cretaceous Argentina (a contemporary of ''Giganotosaurus'' that looked like Scrat from ''WesternAnimation/IceAge''), the platypus-like monotreme ''Stereopodon'' of Early Cretaceous Australia, the badger-sized herbivore of ''Adalatherium'' of Late Cretaceous Madagascar (depicted in ''Series/PrehistoricPlanet''), the possum-like marsupial-relative ''Alphadon'' of Late Cretaceous Canada, the jerboa-like ''Zalambdalestes'' (which lived alongside ''Velociraptor'' in Late Cretaceous Mongolia), and the Late Cretaceous North American multituberculates ''Cimolodon'' (whose order survived the Great Dino Extinction, only to be outcompeted by rodents in the Late Eocene). [[LongList Phew!]]

''Livyatan'' was not the only one of its kind. Throughout the Miocene lived similar sperm whale-relatives of smaller size and with smaller (but still huge) teeth: their scientific names recall the one of the modern sperm whale, ''Physeter'', with a prefix ahead. Among the most notorious of these are the 15ft-long ''Acrophyseter'' from Middle Miocene Peru, the 23ft-long ''Brygmophyseter'' from Middle Miocene Japan (portrayed in ''Series/JurassicFightClub'' as the rival of Megalodon), and the 23ft-long ''Zygophyseter'' from Late Miocene Italy; ''Acrophyseter'' and ''Zygophyseter'' stand out for having smaller spermaceti organs than the others, giving them a dolphin-like beak. Together with ''Livyatan'' are nicknamed "macroraptorial sperm whales" (not considered an actual taxonomic group within Physeteroidea). These animals were all apex predators that occupied the same niche as the modern orca; they certainly would have given Megalodon a run for its money as King of the Cenozoic Ocean.

!! Small Primate Relatives: ''[[http://en.wikipedia.org/wiki/Plesiadapis Plesiadapis]]'', ''[[http://en.wikipedia.org/wiki/Planetetherium Planetetherium]]'' & ''[[http://en.wikipedia.org/wiki/Purgatorius Purgatorius]]'' *

Despite this, size doesn't always matter to make extinct mammals interesting to people. ''Plesiadapis'' was an archaic primate that lived at the start of the Cenozoic, similar to a lemur but with gnawing teeth like a rodent (MixAndMatchCritter again in play). Today, only one species of living lemur has gnawing incisors, the unrelated Aye-Aye of Madagascar (''Daubentonia [[ExactlyWhatItSaysOnTheTin madagascariensis]]'').

''Purgatorius'', named after Purgatory Hill, was a small, more generic-looking shrew-like placental that lived both before and after the Great Dinosaur Extinction, considered a distant primate-relative. ''Didelphodon'' ("possum tooth", see the last paragraph for this) was, as its name suggests, an extinct relative of modern marsupials - but not a true marsupial unlike what was once thought by scientists, while the Australian ''Thylacoleo'', ''Procoptodon'' and ''Diprotodon'' were true marsupials related with kangaroos and koalas. Also, the famed "marsupial" pseudo-sabertoothed cat ''Thylacosmilus'' of South America, according to recent studies, is not a proper marsupial but only a relative.

As ''Purgatorius'' was found in the Hell Creek North American formation hailing 66-68 mya, it would've coexisted with the very last dinosaurs, like ''UsefulNotes/TyrannosaurusRex'', ''[[SocialOrnithopod Edmontosaurus]]'', ''[[ToughArmoredDinosaur Ankylosaurus]]'', and ''[[TemperCeratops Triceratops]]'', and the last pterosaurs like ''Quetzalcoatlus''. ''Purgatorius'' has been also famous because it used to be considered the earliest primate or primate-ancestor, often imagined similar to the modern tree-shrew (more correctly called the tupay) in look; so is frequently-mentioned in the sources talking about the evolution of humans together with the more "evolved" ''Plesiadapis'' ("near-monkey").

Another extinct early primate-relative living a bit after the dinos' mass extinction was able to glide with its skin membranes and was similar to the modern colugo or "flying lemur": ''Planetetherium'', meaning "gliding beast". This mammal has also been frequently portrayed in prehistoric books and paleo-art, but this time not linked with the evolution of humans -- but sometimes with the evolution of bats: because of its flying-squirrel-like "wings", it was [[ScienceMarchesOn once]] often considered one of their possible ancestors.

It's not known if ''Didelphodon'' had a pouch like kangaroos, or was pouchless like many north and South American true possums (family Didelphidae). The didelphodont makes a curious and unique pop-culture case: it used to be a very obscure animal, one of the many generic small mammals of the Cretaceous and seldomly portrayed even in prehistory book... until year 1999: it became abruptly famous in that year when was portrayed in the WWD sixth episode, “Death of a Dynasty”, as the annoying mammal stealing eggs and as an opportunistic scavenger, in a sense the "villain" of the story (other than the giant comet) in which the last North American dinosaurs are the protagonists. In the show, and official science, [[ScienceMarchesOn it was depicted as a badger/Tasmanian devil like creature]], but it was very recently found that it resembled and behaved more like an otter, so the WWD portrayal is very inaccurate now apart for the size of the animal. Yet, thanks to the show, it is still commonly seen as the main “Hell Creek mammal” coexisting with the last dinosaurs, together with the more classic choice of ''Purgatorius''.

The group ''Didelphodon'' belongs to (Stagodontidae) went extinct 66mya with the dinosaurs, though the Early Cenozoic ''Eobrasilia'' ("early [[ExactlyWhatItSaysOnTheTin brazilian]])" might be a member of the group. Other examples of small mammals living alongside the last giant reptiles of the Mesozoic are the insectivorous ''Zalambdalestes'' and ''Deltatheridium'' (both living with ''[[RaptorAttack Velociraptor]]'' in Cretaceous Asia) and the herbivorous Multitubercolates, that survived the Great Dino Extinction and reached the Middle Cenozoic until they were outcompeted by rodents and hares around the world.

Sorry, these aren't here. If you're looking for ''Protosiren'', ''Titanohyrax'', ''Teleoceras'', ''Metamynodon'', ''Homotherium'', ''Borophagus'', ''Cynodictis'', ''Viverravus'', ''Pelorovis'', ''Titanotylopus'', ''Protoceras'', ''Prolibytherium'', ''Remigtonocetus'', ''Eurhinodelphis'', ''Merycoidodon'', ''Anoplotherium'', ''Thalassocnus'', ''Stegotherium'', ''Palaeolagus'', ''Palaeocastor'', ''Phoberomys'', ''Icaronycteris'', ''Dinopithecus'', ''Archaeoindris'', ''Phascolonus'', ''Palorchestes'', ''Zaglossus'', and others, see [[UsefulNotes/PrehistoricLifeMammals here.]]

Megalania ("big tearer") has been known far longer; it was described by Richard Owen (the dinosaurs' TropeNamer) in the 19th century. It was a type of monitor lizard, extremely closely related to modern goannas and Komodo dragons, to the point that in 2004, it was put in the same genus as modern monitors, ''Varanus'', after spending nearly a century-and-a-half as its own genus, "''Megalania''" ''prisca'' (and thus renamed ''Varanus priscus''[[note]]the change to the species name was to comply to the Latin rules of grammar, as ''Varanus'' is masculine and ''Megalania'' is feminine[[/note]]); Megalania still remains in use as a common informal name for it though. It was one of the top predators of Ice Age Australia, in competition with the marsupial lion ''Thylacoleo'' (see below) and some land-dwelling crocodilians (the [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Mekosuchines]]). Megalania is the largest-known fully terrestrial lizard of all time, but due to the lack of complete or near-complete skeletons, its exact size is controversial (estimates range between 10-25 feet long; pop-media tends to exaggerate it). Its behavior was arguably similar to that of modern goannas, and like them, it had a snake-like forked tongue to detect odors from the soil, laid eggs, and was likely an intelligent animal with complex behavior. We don't know, however, if it was venomous like the Komodo dragon, but if it was, it would have been ''the largest venomous animal ever''. Megalania went extinct only a few thousand years ago, along with most of the Australian megafauna, at about the same time as the extinction of the mammoths and sabertooths; it may have been killed at least indirectly by the fires created by the first prehistoric human colonizers of the LandDownUnder.

#'''Entry Time:''' the 2000s for the megalania and 2010s for ''Titanoboa''
#'''TropeMaker:''' ''Series/MonstersWeMet'' (the megalania), ''Series/PrimevalNewWorld'' (''Titanoboa'')

These two giant mammals from the LandDownUnder are more excellent examples of MixAndMatchCritters, and the two most commonly-portrayed herbivorous prehistoric marsupials in media because of [[BiggerIsBetter their size]]. They could have been portrayed even in prehistoric paintings made by the ancient Aborigines of the Stone Age, maybe even on the Uluru. Some also believe stories of these animals (as well as the megalania mentioned above and ''Thylacoleo'' below) have been preserved in Australian Aboriginal mythology.

The marsupial lion was so-called because its body shape, sharp claws, and short head remember modern big cats. But unlike the latter, it had ''rodent-like incisors'' (like wombats and ''Diprotodon'') instead of the classic fangs, and "guillotines" similar to those the Paleozoic fish ''Dunkleosteus'' instead of carnassial molars. Scientists once thought ''Thylacoleo'' was herbivorous like a wombat or rabbit because of its strange teeth; [[ScienceMarchesOn they now know]] it was predatory, thanks to bite marks on the bones of other extinct marsupials. Not only that, it may have been ''the most efficient'' mammalian predator ever. Despite being no bigger than a jaguar, it was likely able to kill even the diprotodonts and giant kangaroos! The combination of retractable ''Velociraptor''-like claws in its powerful forelimbs (perfect for scaling trees to ambush victims) and guillotines in its mouth proved a powerful killing arsenal, able to slice the neck of prey and deliver instant death. Were it not for the presence of two larger, faster, and equally well-armed reptilian predators -- the terrestrial crocodile ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Quinkana]]'' and the megalania, the giant goanna -- it would have been the continent's unrivalled predator. And yet despite all this, its close relationships and the unusual shape of its teeth tell us it was descended from ''herbivorous'' ancestors.

We often think of Ice Age animals as primordial beasts of a bygone era, but the truth is that they were all very modern animals adapted to today's world; virtually all living and historically-extinct animals we know of co-existed with them, including us humans, and in another timeline, the Pleistocene megafauna would still be roaming Earth today. In the case of Australia's ancient giants -- the marsupial lion, the diprotodont, the giant short-faced kangaroo, the megalania, and others -- it seems they all met an untimely end at the hands of the first Aboriginals, who set fires to grow different plant species, consequently starving their prey into extinction. The introduction of the dingo a few centuries later spelled the same fate for the other main mammalian predators of prehistoric Australia -- the smaller thylacines (''Thylacinus cynocephalus''; see Historically-Extinct Mammals) and Tasmanian devils. While the devils still survive today, the thylacine missed the chance to be observed by modern wildlife lovers only by a matter of decades. Forget {{Prehistoric Monster}}s, it seems that HumansAreTheRealMonsters.

Whenever the putative "ur-horse" ''Hyracotherium''/''Eohippus'' shows up in media, expect it to be portrayed as a RedShirt, usually falling prey to the giant flightless bird ''Gastornis''/"Diatryma". But after ScienceMarchesOn, we know it's highly unlikely for the bird to have had any interest in the small ungulates due to its herbivorous diet -- the "ur-horses" might have instead been prey for terrestrial crocodilians like ''Boverisuchus''/"Pristichampsus", being "[[StockPhrase as large as a fox terrier]]", to use a classic description in paleo-books. Among fictional appearances, the most notable was perhaps Creator/RayHarryhausen's cowboys-versus-dinosaurs film ''Film/TheValleyOfGwangi''.

''Mesonyx'' ("middle-nail") was an Eocene North American mammal similar in size and shape to a strange dog or hyena with a big head and long tail, but with [[MixAndMatchCritter primitive hooves]] like ''Phenacodus'' or ''Eohippus''. It was one of the first mammalian predators, but being no bigger than a modern dog, it was definitely not the apex predator in a world dominated by terrestrial crocodilians like ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Boverisuchus]]'' (formerly ''Pristichampsus'') and huge flightless birds like ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Gastornis]]'' (which is now considered a herbivore). It was the namesake of a group of carnivorous basal ungulate-relatives called the mesonychians, who are most famous for having once thought to have been the ancestors of the cetaceans (the mysterious ''Andrewsarchus'' mentioned above was once considered part of this group). The traditional image was that ''Mesonyx'' and is relatives roamed the coasts in search of dead fish and carcasses,, and that this was the kick-off of the evolution of whales. This could explain why the ''Walking With Beasts'' producers decided to show ''Andrewsarchus'' near the shore in search of turtles in its first relevant scene. Nowadays, whales are considered true artiodactyls descended from the same ancestor as hippos, while mesonychians are believed to be fully terrestrial predators that ruled the mammalian hunter niche in Asia, Europe, and North America during the Paleocene and Eocene before vanishing in the Early Oligocene.

Carnivorous ungulate-relatives are strange enough already, but few groups of extinct mammals have baffled scientists as much as the demostylians, the only totally extinct group of sea mammals ever. Debate rages over which modern mammal group this lineage of ''true'' sea mammals is most closely related to -- they are traditionally believed to be afrotheres related to sea-cows and elephants, but the fact they are exclusively from the North Pacific contradicts the consistently African and Atlantic evolutionary history of the afrotheres, leading other scientists to propose they are instead perissodactyls or perissodactyl-relatives, closer to horses and rhinos. However, the jury remains out for now. Desmostylians looked a bit like hippos but with shorter hindlimbs than forelimbs and smaller heads. Also like hippos, they had small tusk-like incisors and canines, except these pointed forward and there were multiple on each jaw. They also possessed uniquely tubercled cheek teeth they used to eat kelp. They were once thought to be amphibious, but later studies suggest they were unable to support their weight on land and thus fully aquatic, mostly power-walking on the bottom like hippos do. ''Desmostylus'' ("bundle-pillar", for the shape of its teeth) is the archetype and the most known of the group, first found by Marsh in USA during the Bone Wars; it lived in shallow coastal seas from Japan to Baja Califonia up to Alaska and Siberia during the Miocene. As a group, the demostylians lasted throughout the Oligocene and Miocene, going extinct as sea-cows rose to prominence and entered the North Pacific (where they also eventually went extinct during historical times). Interestingly, the demostylians are very popular in Japan, where they are among the most well-known groups of prehistoric mammals, due to the many fossils of them found there.

''All'' mammals were small and rodent-shaped in their evolutionary beginnings. Some became larger and more derived after the extinction of the dinosaurs, but none to the same level as whales.

The first cetaceans probably spent much of their time on land, feeding on dead fish and drowned animals. ''Pakicetus'' ("Pakistan whale") is the traditionally most-portrayed of them. Found in Pakistan in the late 20th century, it was still four-limbed and looked nothing like a whale, but had a long tail (the typical archaic trait of the earliest ungulates), anticipating the powerful muscular tail of later cetaceans. It was already a good swimmer, but probably swam using its legs like land mammals and seals — not yet its tail, which arguably acted as a rudder. Its nostrils were still placed at the top of its snout like a land mammal, but its ears already showed specializations for hearing underwater like a modern whale (we don't know if it had still external ears or had already lost them). This combination of land and water adaptations makes ''Pakicetus'' another excellent example of a MixAndMatchCritter.

Discovered only in the early 1990s (a decade after ''Pakicetus''), ''Ambulocetus natans'' (lit. "walking whale") was also found in Pakistan. It was similar to the former but bigger, with shorter limbs, palmated feet, and a more powerful tail. At the time of its discovery it was celebrated in media as the "missing link" between the still terrestrial-looking ''Pakicetus'' and more modern whales like ''Basilosaurus''. Maybe because of this fame, ''Ambulocetus'' was chosen as the archetypical early whale in 2001's first episode of ''Series/WalkingWithBeasts'', but was incorrectly shown [[MisplacedWildlife in Europe instead of Asia]] and interacting with critters known from the German Messel Tarpits like ''Leptictidium'' above. In the show, ''Ambulocetus'' was portrayed as a hairy croc-like swimmer and an ambush-hunter of small land mammals, like a modern Nile crocodile; actually, like ''Pakicetus'', its precise appearance and lifestyle is unknown. It may have been a specialist fish-hunter, like modern otters.

Both these early whale-ancestors had the same two tooth shapes in their jaws as ''Basilosaurus'', but being descendants of true ungulates, ''Pakicetus'' may not have been completely zoophagous, unlike the most fishy basilosaur. [[ScienceMarchesOn Recent research]] seems to indicate that ''Ambulocetus'' was already ''fully aquatic'', thus not really deserving the name "walking whale", but nomenclature rules being what they are, it's stuck with it. If true, it used its splayed limbs only as paddles to swim underwater or to "walk" only upon the bottom of water basins, was probably entirely zoophagous like typical toothed cetaceans, and feeding mainly on water creatures like them.

Both ''Pakicetus'' and ''Ambulocetus'' can be shown widely differently in paleo-art and paleo-books: sometimes they are portrayed hairy, sometimes naked-skinned like a modern whale. ''Pakicetus'' in old paleo-art is often shown with seal-like limbs, but today it's given more often dog-like paws. ''Ambulocetus'' can be shown fully aquatic or not according to the period. Apart of the lack of dorsal sail, they could be considered in anatomy the mammalian equivalents of the famous dinosaur ''Spinosaurus'', tough obviously both much smaller than it.

A 2008 discovery made in Peru, ''Livyatan melvillei'' could make appearing the so-much celebrated "prehistoric killer whale" ''Basilosaurus'' quite insignificant in comparison. Indeed, it possesses what may be the largest functional teeth of any animal ever: that is, not counting "tusks" like the elephant, mammoth, walrus, and narwhal ones. The record-holding about the biggest teeth of all times belongs to giant extinct elephants like those of the genus ''Mammuthus'' and ''Palaeoloxodon'', see the folder above.

The size of the partially preserved skull indicates that ''Livyatan'' reached a length between 15-20 meters / 44-57 feet, like the modern giant sperm-whale (''Physeter macrocephalus''), possessing a head three meters long but twice shorter than a large head of a male giant sperm-whale of our days, recalling perhaps in shape more the head of an orca (the modern "killer whale", but actually the biggest living dolphin). ''Livyatan'' was overall more similar to the living sperm whale and belonged to its same clade, the Physeteroids. It was also related to the modern dwarf and pygmy sperm whales (the Kogiidae), but only distantly with modern giant dolphins like the orcas and pilot-whales (''Orcinus'', ''Globicephala'', ''Pseudorca'', all of the Delphinidae family) or the other Odontocetans, aka the living toothy cetaceans. ''Lyviatan'', like all odontocetans, had one single blowhole on its head, correspondent to the left nostril of the land mammals, and a fatty body on its head (the "melon") to help echolocation -- all specialized odontocetans traits, missing in the archaeocetans ''Basilosaurus'', ''Ambulocetus'', and ''Pakicetus'', which had two symmetrical nostrils like all the other mammals.

Like a true orca the lyviatan had teeth in both of its jaws, and its skull looks externally more like the orca's one than the modern sperm whale's one: the umpteenth example of a MixAndMatchCritter prehistoric mammal. To have an idea of the lyviatan's overall appearance, think [[WesternAnimation/{{Pinocchio}} Monstro]], but smaller and without the rorqual-like underbelly ridges present in the Disney's critter. The teeth of this ancient giant of the seas were really massive, even bigger than those of the Megalodon Shark or the Basilosaur whale: at their largest growing to a little over a foot in length. We don't know if it had the spermaceti organ, the hallmark trait of the modern sperm-whales that gives them their name, because the spermaceti is made by an oily soft material that doesn't preserve in fossilization in normal conditions.

''Livyatan'' was initially named "''Leviathan''" by its describer, but nomenclature rules soon changed its name; the second name has a Greek/Latin graphy, the first has the Hebraic one. Whatever the name, this cetacean is believed to have been one of the two area's apex predators, along with the giant shark ''C. megalodon'', who lived in the same area at the same time. It's also theorized that they may have had a similar taste in preferred prey too: baleen whales, aka the Mysticetans. That is, they likely hunted even more powerful preys than the modern giant and colossal squids eaten by proper sperm whales today, or the prey eaten by the smaller-mouthed ''Basilosaurus''. Maybe ''Livyatan'' was even able to kill an adult Megalodon Shark, like modern orcas do sometimes with the Great Whites.

A tooth discovered Beaumaris Bay, Australia in 2016 seems to indicate that ''melvillei''--or a closely related species--may have had a wider habitat range than previously indicated, and existed in the area for another two million years after the time period in which the Peruvian population of ''melvillei'' is known to have occurred. However, as we only have one tooth to go on, at the time of writing it's mostly speculation.

It also happens to be one of those prehistoric animals whose name is a reference, too. "Livyatan" is the Hebrew name for the legendary Biblical sea monster Leviathan (note that the translation of the word "whale" in modern Hebrew is just "livyatan"), and "melvillei" is coined after Herman Melville, the author of ''[[Literature/MobyDick Moby-Dick]]''. Other similar contemporaneous sperm-whale relatives with smaller size and smaller (but still huge) teeth have been found in different places of the world about the same time of the discover of ''Livyatan'', or a bit earlier (the first emerged in the nineties): their scientific names recall the one of the modern giant sperm-whale, ''Physeter'', with a prefix ahead. They were: ''Acrophyseter'' from Peru, ''Brygmophyseter'' from Japan (portrayed in ''Series/JurassicFightClub'' as the rival of megalodon), and ''Zygophyseter'' from Italy. Overall, ''Lyviatan'' and all these cetaceans are nicknamed "macroraptorial sperm-whales", or more simply, the Macroraptorials. They could not form a natural group, though, but all them were related with the true sperm whale of the modern oceans.

# '''Entry Time:''' TheNewTens (''Lyviatan'')
# '''TropeMaker:''' Its size and power and its rivalry against the Megalodon shark

''Coryphodon'' was one of the biggest mammals of the Early Eocene, the size of a large cow. It lived roughly alongside the famous bird ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Gastornis]]'', as well as ''Eohippus'' and ''Uintatherium'', in North America. It was very similar to a hornless uintathere, with small tusk-like canines like the latter, and is classically compared with a hippo. Because of this, ''Coryphodon'' was once considered an early ungulate-relative; in actuality, it was a member of the extinct pantodonts, an extremely basal Palaeocene-Eocene group composed of the first large, plant-eating land mammals, with ''Coryphodon'' being one of the biggest members. Though smaller than other later herbivorous mammals, an adult coryphodont probably feared no predators except for perhaps large crocodilians. Classic portraits often show the coryphodont as amphibious like a hippopotamus, but it could have been more terrestrial. It was often believed slow and had actually a very small brain, but again, this doesn't mean it was harmless and/or witless.

''Phenacodus'' was much smaller (about the size of the better-known ''Eohippus''), and also lived in the Early Eocene. It was very generic, with dentition suited for various foods (probably was a mainly-herbivorous omnivore), and with an archaic long tail typical of the earliest "hoofed mammals". It was formerly considered part of a group of primitive ungulates known as "condylarths", but this order has been disbanded, and ''Phenacodus'' is now considered to have most likely been a relative of the perissodactyls or even a true primitive member of this group. When the giant bird 'Gastornis''/"Diaryma" was believed to have been the superpredator of the Early Eocene, ''Phenacodus'' was considered one of its possible prey, just like ''Eohippus''.

!! Stuck in Tarpits: ''[[http://en.wikipedia.org/wiki/Leptictidium Leptictidium]]'', ''[[http://en.wikipedia.org/wiki/Eurotamandua Eurotamandua]]'' & ''[[http://en.wikipedia.org/wiki/Eomanis Eomanis]]'' *

''Leptictidium'', despite its look, was totally different from the two rodents ''Castoroides'' and ''Ceratogaulus'' described in the previous folder: it was a smallish (the size of a medium dog), short-armed and long-legged "insectivore" found in Europe from the start of the Mammal Age, once put in the Insectivorans or in the equally artificial group named Proteutherians ("first eutherians"); today is placed in the eponymous Leptictidians.

It's probably the most famous of those mammals which were preserved in the German Messel Tarpits (see UsefulNotes/PrehistoricLifeMammals), and it's always been one of the most peculiar of them all — others include early pangolins, hedgehogs, early bats, primitive ungulates, small carnivores, and ancient primates. Arguably because of its MixAndMatchCritter look, it was chosen as the main character of the first episode of ''Series/WalkingWithBeasts'', set in Eocene Germany.

''Leptictidium'' was not related to any modern mammalian group, not even modern "insectivores" like hedgehogs, moles or shrews, and looked more like a small kangaroo or a jerboa. The modern animal that mostly resembled it is maybe ''Rhynchocyon'', the "elephant-shrew" of Africa. But we don't know if it actually hopped like a kangaroo like in ''WWB'' or ran like a miniature dinosaur; some portrayals prefer the first choice, others the second. Anyway, judging from its teeth, it was arguably a predator of insects or small vertebrates. Additionally, we don't know if it had a mobile nose like a shrew.

Among the numerous mammals found in the German Messel Pits, also worth of note are two animals belonging to a very ancient group: ''Eomanis'' and ''Eurotamandua'' are the first known pangolins. As expected from Messel animals, their remains include soft parts of their body. Their shape was already that of their modern relatives, with long muzzles, short legs with robust claws, long tails, and a long sticky tongue to catch ants and termites. However, their external look was ''very'' different from each other: ''Eomanis'' had the familiar tile-like scales covering most of its body, and was virtually identical to modern pangolins; ''Eurotamandua'' was ''hairy'' and resembled more a modern South American anteater than a pangolin -- indeed, it was long classified as a proper anteater. The names of both animals are referred to this older classification: ''Eomanis'' means “dawn pangolin”, ''Eurotamandua'' means “European tamandua” (Tamandua is the name of a modern kind of middle-sized anteater of Central and Southern America).

!! Near the Ancient Shores: ''[[http://en.wikipedia.org/wiki/Mesonyx Mesonyx]]'' & ''[[http://en.wikipedia.org/wiki/Desmostylus Desmostylus]]'' *

''Mesonyx'' ("middle-nail") was similar in size and shape to a strange [[{{Pun}} dog]] or hyena with a big head and long tail, but with [[MixAndMatchCritter hoof-like nails]] like ''Phenacodus'' or ''Eohippus''. It was one of the first mammalian predators/scavengers comparable in size to a human — but still smaller than the allegedly meat-eating bird ''Gastornis''; thus it was once considered an [[{{Pun}} underdog]] of the latter. But its fame is due mainly to the fact it and its relatives (together called Mesonychians) were once thought to have been the ancestors of the cetaceans: it was said they roamed the coasts in search of dead fish and carcasses, and that this was the kick-off of the evolution of whales.

Together, ''Mesonyx'', ''Phenacodus'' and other less-known early mammals were put together in the artificial grouping named the [[http://en.wikipedia.org/wiki/Condylarth Condylarths]]. Today they are usually believed related with the even-toed ungulates (artiodactyls). Interestingly, ''Andrewsarchus'' has traditionally been depicted as an oversized ''Mesonyx'' because was considered a giant relative of the latter. This could explain why the ''Walking With Beasts'' producers decided to show it near the shore in search of turtles in its first relevant scene.

A lineage of ''true'' sea mammals, this time related with elephants, sea-cows, and hyraxes, makes the only totally extinct group of sea mammals ever: the Desmostylians. They were a bit similar to small hippopotamuses but with shorter hindlimbs than forelimbs, thus having been compared with "herbivorous seals". ''Desmostylus'' ("bundle-pillar") is the prototype and the most known of the group.

''Desmostylus'' was first-found by Marsh in the USA during the Bone Wars; the group as a whole lasted relatively few, living 20 million years in the middle-Caenozoic seas around the world and got extinct before the Ice Ages. They had four protruding tusk-like incisors (a couple for each jaw) similar to those of early proboscideans like ''Moeritherium'', making them looking a bit like walruses; but their tusks were shorter, and unlike the shellfish-eating walrus the desmostylus ate weeds like the closely-related dugongs and manatees, also thanks to its uniquely-tubercled cheek-teeth.

Like sloths, chalicotheres probably weren't especially fast runners compared to other ungulates due to their frame (yes, they were ungulates!), with short hindlegs and longer forelegs (the latter being up to ''twice'' the length of the former). Nonetheless, they were powerful and muscular animals (the biggest were nearly 3m tall and weighed about a ton) and arguably not an easy target for even the biggest mammalian predators. We don't know how long/dense their hair was, or if they had it at all, as with almost all prehistoric mammals -- except those found frozen in ice.

''Coryphodon'' was one of the biggest mammals of the Eocene, the size of a large cattle (but still smaller than ''Uintatherium'', the brontotheres, and ''Arsinoitherium'') and lived roughly alongside the famous bird ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Gastornis]]''. It was very similar to a hornless uintathere, with small tusk-like canines like the latter, is classically compared with a hippo; ''Coryphodon'' is considered a highly derived member of the Pantodonts (the first large, plant-eating land mammals), whose was one of the biggest members. Though smaller than other later herbivorous mammals, as an adult the coryphodont probably feared no predators except for perhaps some giant reptiles (crocodilians, constrictor snakes). Classic portraits often show the coryphodont amphibious like a hippopotamus, but it could have been more terrestrial. It was often believed slow and had actually a very small brain, but again, this doesn't mean it was harmless and/or witless.

''Phenacodus'' was much smaller (about the size of the better-known ''Eohippus''), and also lived in the Eocene. It was very generic, with dentition suited for various foods (probably was a mainly-herbivorous omnivore), and with an archaic long tail typical of the earliest "hoofed mammals". It was probably a relative of the perissodactyls or even a true primitive member of this group. When the giant bird ''Diatryma''/''Gastornis'' was believed to have been the superpredator of the Early Cenozoic, ''Phenacodus'' was considered one of its possible prey, just like ''Eohippus''. It was once considered a herbivorous member of the Condylarths: Mesonychians were considered carnivorous members of the same group.

Although "carnivore" literally and commonly just means "meat-eater", in cladistics it refers to members of the order Carnivora (the less ambiguous term for members of this group is "carnivoran"). The vast majority of large carnivorous land mammals are carnivorans — bears, canids, cats, hyenas — but there have been exceptions: not counting marsupials like the pseudo-felines ''Thylacosmilus'' & ''Thylacoleo'', there were also the Creodonts and their relatives, the Oxyaenids.

Creodontians were related to true carnivorans, but were more primitive. They had smaller brains (like most early mammals that lived before the Ice Age), and with different cheek teeth than true carnivorans; they nonetheless often had powerful jaws with a stronger bite than modern carnivores (Creodont means "meat tooth").

''Hyaenodon'' (often misspelled "Hyaenadon", "Hyenodon", or "Hyenadon"), the most iconic and portrayed creodont in media, has a name that is not mere coincidence: despite being more similar in shape to a short-limbed, long-tailed wolf, it had the typical crushing jaws/teeth of a hyena — hence the name, "hyena tooth". Scientists tended to depict the hyaenodont as a scavenger because of this, but since RealLife spotted hyenas are more often active hunters, contrary to popular belief, the bone-crushing jaws of their ancient namesake don't rule out more predatory behavior.

Indeed, in the third episode of ''Series/WalkingWithBeasts'', an oversized ''Hyaenodon'' (the biggest species in reality was no larger than a bull, and ''not'' "as big as rhinos" as said in the show!) is the main predator of the story, capable of killing with extreme ease two-ton chalicotheres, and digesting [[ExtremeOmnivore even their teeth]] — based on modern hyenas, which can dissolve bones in their stomachs. But these claims are mere speculation: note that most modern meat-eating mammals can't digest bones, much less enamel-covered teeth. It may also have been shown as more agile than it was in RealLife, since a large specimen of ''Hyaenodon'' was arguably rather slow-moving compared with modern wolves, cats, or hyenas, not only being heavier but also having shorter feet. Maybe in RealLife it resembled more a gigantic wolverine than to a wolf or a hyena in appearance and movements.

In the show the hyaenodon appears as a [[AllAnimalsAreDogs dog-like]] critter with a look kind of similar to the famous Thylacine or Tasmanian wolf, with small "saber" upper canines, and growling in the same manner as an AngryGuardDog when approaching the young indricothere in a pack — again, there's no proof of wolf-like pack behavior or even growling. In short, it's portrayed like a gigantic cross between a wolf and a hyena, but in reality, it was related to neither. Note also that other creodonts were even bigger than the hyaenodont, ex. the one-ton ''[[UsefulNotes/PrehistoricLifeMammals Megistotherium]]'' ("huge beast").

''Sarkastodon'' (also meaning "meat-tooth", like the word creodont) was also bigger than ''Hyaenodon'', and was once believed a creodont, but now is classified in another group, the Oxyaenids, which were possibly closer to ''pangolins'' than to true creodonts. Like the hyaenodont, we don't know much of its lifestyle apart from the fact that was specialized for meat-eating; there is the possibility, however, that like many modern Carnivorans, both were not pure flesh-eaters but omnivores instead. Even felines, usually described as "the most carnivorous of the modern carnivores", very rarely eat ''fruit'' other than meat. See [[https://youtu.be/0Wkt-_8cCIc these]] [[https://youtu.be/yT_Gabq7c6E images]].

Other extinct mammals were true carnivores, but deceptively looked like members of modern families of the carnivorans (felids, canids, ursids, hyaenids, mustelids, etc.).

''Eusmilus'' ("true saber"), for example, was an almost-perfect copy of a saber-toothed cat of the Felidae in shape, size, and anatomy, but actually belonged to a distinct lineage of feliforms, the Nimravids, which also included ''Nimravus'' and ''Dinictis'' among the others. Nimravids lived earlier than ''Smilodon'' and most other true sabertooths; ''Eusmilus'' had shorter legs but particularly long sabers, almost as long as ''Smilodon'''s and longer than other true saber-toothed cats like ''Homotherium'' or ''Megantereon''. Its behaviour and predation style are uncertain; some say ''Eusmilus'' was less intelligent than smilodonts and their kin, but that's only a guess, obviously.

''Amphicyon'' means "half-dog", an apt term because it was related to canines but was not one of them — it's the namesake of its own family of carnivores, the caniform Amphicyonids. Its size and appearance were rather in the middle between [[MixAndMatchCritter a long-tailed wolf, a slender bear, and a big weasel]]; according to recent classifications, the Amphycyonids were closer to the bears (ursids) than to the dogs (canids), and were also related to raccoons (procyonids), skunks (mephitids), and weasels, martens, badgers, otters, wolverines etc. (true mustelids). It's uncertain if the amphicyon was an almost-pure carnivore like a feline or an omnivore like most bears and several canids and mustelids. Like ''Eusmilus'', ''Amphicyon'' existed in the middle of the Mammal Age, in the Neogene period, well before the Ice Ages.

Chalicotheres are typically regarded as some of the best examples of MixAndMatchCritter among prehistoric mammals, even more than ''Arsinoitherium''. They all had the head of a horse (but without the strong horse's incisors), the body shape often of a gorilla, and bear-like forelimbs with hooked claws for pulling down branches or excavating the soil in search of roots: some nickname them [[MixAndMatchCritter gorilla-horses]], and confront them with the therizinosaur dinosaurs or the giant ground sloths like ''Megatherium''.

Like sloths, chalicotheres probably weren't especially fast runners compared with other ungulates because of their frame (yes, they were ungulates!), with short hindlegs and longer forelegs, but were nonetheless powerful and muscular animals and arguably not an easy target for even the biggest mammalian predators. We don't know how long/dense their hair was, or if they had it at all, as with almost all prehistoric mammals - except those found frozen in ice or stuck in ancient tarpits, which have often preserved some remains of skin.

A very successful group of hoofed mammals, chalicotheres, despite their un-ungulate-like appearance, were perissodactyls or odd-toed ungulates, distantly related to horses, rhinos and tapirs (like the aforementioned brontotheres), but their body plan was quite modified from the original ungulate shape — more so than any other ungulate except for obviously the cetaceans, which descend directly from land artiodactyls — with the nails of some chalicotheres more resembling ''claws'' than hooves. Chalicotheres roamed for a long time in most continents, and [[WildMassGuessing some think]] the famous "Nandi bear" that allegedly lives in modern African rainforests is a surviving chalicothere.

The two most well-known family members are the North American ''Moropus'' and the Asian namesake ''Chalicotherium'', both from the middle of the Cenozoic. The former (lit. "silly foot" because its nails had a split in the middle) was the more horse-like in appearance of the two, with forelimbs not much longer than hindlimbs, and probably walked like a normal ungulate. The latter (half again taller than a human) had forelegs ''twice'' the length of its hindlegs, and its "hands" had huge curved sloth-like claws which possibly obliged it to literally ''knuckle-walk'' like a gorilla to protect them against damage, just like modern giant anteaters do (and probably many extinct ground sloths as well). Similar to ''Chalicotherium'' but smaller was the European ''[[http://en.wikipedia.org/wiki/Anisodon Anisodon]]'', once considered a ''Chalicotherium'' species.

An unnamed "chalicotere" (arguably ''Chalicotherium'' itself) is portrayed in the third episode of ''WWB'' as a rather torpid animal with a very [[PandaingToTheAudience giant panda]]-like face, that makes it look more harmless than other, more badass popular representations of chalicotherians. Here, it mainly appears as fodder for other large mammals of the time — the predatory ''Hyaenodon'' and the scavenging entelodonts, to be precise. Another species, the African ''[[http://en.wikipedia.org/wiki/Ancylotherium Ancylotherium]]'', was shown in the fourth episode of ''Beasts'' as an [[HerbivoresAreFriendly inoffensive]], easily-frightened neighbor of the australopithecines. This one in RealLife was closer to ''Moropus'' than to ''Chalicotherium'', and was one of the last surviving genera of chalicotherians: it reached the Early Pleistocene epoch, before ultimately going extinct probably due to the changing colder climate conditions. All this not counting the improperly-named [[OurCryptidsAreMoreMysterious cryptid]] Nandi Bear, of course.

# '''Entry Time:''' undetermined
# '''TropeMaker:''' documentary media

Let's return to the even-toed ungulates: alongside the Giant Deer ''Megaloceros'', there was another, very different-looking kind of extinct artiodactyl that has achieved some popularity: the Entelodontids.

They were among the several prehistoric artiodactyls that resembled boars in shape and possibly habits. Entelodonts ("complete teeth") had the same overall body plan as pigs but with usually a hump on their shoulders like bison, and were once thought to be closely related to pigs, but have [[ScienceMarchesOn recently]] turned out to be closer to hippos and whales. They were bison-sized at the most, and the bony knobs on their heads and jaws made them resemble giant warthogs. But their tusks were straight like those of peccaries, much smaller than a warthog's or a babirusa's, and didn't protrude out of the mouth. The exact shape of their snout is unknown, but it's unlikely that they had pig-like noses as shown in classic paleo-art, especially given the recent theories which classify them as hippo relatives.

The food habits of these critters are still unclear: they might have been scavengers that drove away small predators from their kill, but also ate vegetation, and might even have been active hunters sometimes, a bit like the omnivorous modern wild boars. Thanks to their strong jaws, they would've been able to crush the bones of corpses to reach the softer marrow inside, but their cheek teeth were flat like those of a horse or a bovine, and their incisors were small: just like modern pigs, peccaries, tapirs, and hippos. The bony knobs on their heads may have protected them against rivals during fights, as shown by "scars" on the skulls of some specimens left by the canines of their conspecifics — they probably could open their mouths wider than boars, but not to the same degree as hippos, which can open their mouth almost 180 degrees!

North American ''Daeodon'' (also called ''Dinohyus'', "terrible pig") is the largest and historically the most-often depicted entelodont, living alongside the chalicothere ''Moropus'' in the Miocene. ''Series/WalkingWithBeasts'' showed an unnamed Asian relative living alongside the "indricothere", and altered its appearance [[RuleOfScary to make it scarier]], exaggerating the opening of its mouth (it's given no cheeks at all, more similar to a cetacean than to a hippopotamus) and also making it [[NoisyNature particularly noisy]] and overly aggressive toward every animal it encounters. Here the entelodonts also appear almost-naked like a warthog or babirusa, but we don't know if in reality entelodontids were mostly covered in bristles like a wild boar or peccary, or not.

''[[http://en.wikipedia.org/wiki/Archaeotherium Archaeotherium]]'' ("ancient beast") and the prototypical ''[[http://en.wikipedia.org/wiki/Entelodon Entelodon]]'' were also Asian. The former was one of the smallest and most ancient entelodonts, the size of a modern boar; the latter was more similar in size to ''Daeodon''. Extinct true pigs of the Suid family included ''Kubanochoerus'' (the biggest, with a head-prominence), ''Metridiochoerus'' (the biggest-tusked), and others: but see UsefulNotes/PrehistoricLifeMammals for these.

These mammals were also artiodactyls, but similar to deer or moose in shape. ''Sivatherium'' was one of the biggest ruminants ever; the largest species, ''Sivatherium giganteum'', was heavier than an average bison, and 2.5m tall at the shoulder — as massive as a giraffe, though less tall. Its names means "[[Myth/HinduMythology Shiva's giant beast]]".

''Sivatherium'' was indeed related to giraffes, but little resembled them. Stocky and short-necked, it had "antlers" quite similar to a moose's, or a pronghorn's if you prefer; these "antlers" were true ''ossicones'' like those of a living giraffe or an okapi, firmly attached to the skull as seen in the ''Sivatherium's'' surviving relatives. Being a ruminant, it arguably "chewed its cud" like a cow or a giraffe in life. Some think it's represented in ancient cave paintings in the Sahara and India; ''Sivatherium'' lived both before and during the Ice Age, going extinct only recently, and roamed across the Old World (where humans underwent most of their evolution). Related with ''Sivatherium'' but smaller was ''Bramatherium'', the "[[Myth/HinduMythology Brahma's beast]]", with its curious four-pronged one ossicone. The Climacoceratids were very similar to giraffes and sivatherines in anatomy, and also had unusually-shaped antler-like "ossicones". Among the other Giraffids, only two animals have survived to today: the proper giraffe and the smaller okapi, both exclusive to Africa.

''Synthetoceras tricornatum'' ("three-horned fused horn") has been traditionally more enigmatic. From Miocene North America, it resembled in shape a common deer or antelope, but had indeed ''three'' horns placed on the head surprisingly similarly to a ''Triceratops'', and the nasal horn was long and two-pronged like that of "Brontotherium" (''Megacerops''), but with pointed ends like a kitchen fork. Its size was more normal, like a big modern antelope: think about a strange sable antelope or gemsbok (Hippotragines), or better, a hartebeest or a wildebeest (Alcelaphines), because of its very long snout and short curved frontal horns. It was arguably a faster runner than the giant sivathere, probably able to jump easily like a deer or a wildebeest. Despite all this, this "mammalian triceratops" was actually more related to camelids and/or tragulids than to deer, pronghorns, giraffes, and antelopes, all true Ruminantia. But since camelids (llamas and camels) and tragulids (chevrotains) also ruminate, ''Synthetoceras'' almost certainly did the same. As with the above-mentioned ''Sivatherium'', ''Synthetoceras'' may be wrongly identified as a true deer or antelope in media.

In older depictions, ''Sivatherium'' was more moose-looking than in the modern ones, in which is often painted with the same colors of a modern giraffe or a modern okapi; ''Synthetoceras'' can be either represented as deer-like or antelope-like according to the artist. But unlike deer, moose, or pronghorn "antelopes", the "syntheto" had perennially-attached horns on its head, like a giraffid, a rhinoceros, or a ceratopsid. If sivatheres' and synthetocerases' prominences were covered in skin or in keratin, this is controversial. Giraffe's ossicones are covered in skin: rhinos' horns are made by hardened hair; ceratopsid horns were covered by keratin like modern bovines, goats, true antelopes, and pronghorns; while deer and moose antlers are ''naked bone'', and covered by hairy skin only at the start of their periodic growth.

Most of them lived in the Mediterranean islands; especially famous is ''[[http://en.wikipedia.org/wiki/Palaeoloxodon_falconeri Palaeoloxodon falconeri]]'' (one of the "straight-tusked elephants") of Sicily and Malta, known the possible link with ancient legends from Greek Antiquity (see below). There was also ''[[https://en.wikipedia.org/wiki/Mammuthus_creticus Mammuthus creticus]]'', the Cretan dwarf mammoth, and ''[[https://en.wikipedia.org/wiki/Palaeoloxodon_cypriotes Palaeoloxodon cypriotes]]'' of Cyprus. Others lived elsewhere; ''[[https://en.wikipedia.org/wiki/Pygmy_mammoth Mammuthus exilis]]'', the Channel Islands mammoth, lived on the Channel Islands off southern California was descended from the gargantuan Columbian mammoth, while Wrangel Island off eastern Siberia and Saint Paul Island off Alaska supported woolly mammoths smaller than the mainland forms (but of the same species). Additionally, dwarfs of the more primitive proboscidean ''[[https://en.wikipedia.org/wiki/Stegodon Stegodon]]'' existed around the same time in Celebes and Flores in Indonesia. All achieved their dwarfism due to the limited resources of island environments and the lack big mainland predators reducing the need to defend themselves with their bulk -- at least until humans drove them all to extinction. As for how they ended up on islands in the first place? In most cases, they swam (elephants are excellent swimmers), while the Wrangel and Saint Paul mammoths walked there due to the lower sea levels of the Ice Age. Interestingly, the "woollies" of Wrangel and Saint Paul managed to survive until about 4,000 years ago, contemporaneous with AncientEgypt. However, dwarf elephants still exist today -- Borneo in Indonesia hosts [[https://en.wikipedia.org/wiki/Borneo_elephant Asian elephants smaller than their mainland and Sumatran counterparts]].

The first whales evolved early in the Mammal Age, in the Eocene, from terrestrial ancestors related to modern even-toed hoofed mammals (especially hippopotamuses). Most early cetaceans were medium-sized, but not ''Basilosaurus cetoides'' ("whale-like king lizard"). This one reached the length of a modern baleen whale or sperm whale: up to 20 m/60 ft, longer than most stock marine reptiles — though still much shorter than a blue whale (''Balaenoptera musculus''). In spite of its length, the basilosaur weighed "only" 20 tons, less than shorter modern whales like the 30-ton humpback (''Megaptera''): this because it was much slenderer, to the point that it's sometimes described as "eel-like". But wait, why does its name end in [[{{Whateversaurus}} -saurus?!?]] Well, when first discovered by Dr. Richard Harlan, its elongated shape was misidentified as a [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles mosasaur]]-like marine reptile: hence its strange, reptile-sounding name, meaning "king lizard". There was an attempt to rename it ''Zeuglodon'' to fix the error, but nomenclature rules prevented that.

Its first remains were discovered in North America in the 19th century, and more were found in the 20th century in Egypt, which at the time ''Basilosaurus'' lived was mainly occupied by a shallow sea. For long the basilosaur was one of the few early cetaceans known by science, together with ''Protocetus'', ''Dorudon'', and few others. ''Pakicetus'', ''Ambulocetus'' and other key "archaeocetans" were discovered only during or after TheEighties, along with the more modern-looking toothed whales ''[[UsefulNotes/PrehistoricLifeMammals Odobenocetops]]'', the huge ''Livyatan melvillei'', and the other "macroraptorial sperm-whales". In ''Basilosaurus''' time, all whales were still active hunters, like modern orcas and sperm whales, but still with differentiated teeth: the anterior ones pointed, the posterior serrated, an old legacy which betrays their origins from land mammals.

''Basilosaurus'' was at the centre of a peculiar hoax in the 1840s by the notorious huckster Alfred Koch. Koch had come into possession of a large number of ''Basilosaurus'' fossils, the remains of at least six different individuals, which he assembled into a gargantuan amalgam and dubbed ''Hydrargos[[note]]or sometimes ''Hydrarchus''[[/note]] sillimani'' (Silliman's Water King, in honour of Prof. Benjamin Silliman, a naturalist who was willing to vouch for its veracity). Koch, making the same mistake as Dr. Harlan before him, assumed the bones were reptilian and presented his creature as a real-life [[SeaSerpent sea serpent]] and the inspiration for the [[Literature/TheBible biblical]] [[KrakenAndLeviathan Leviathan]], but he was met with ridicule and skepticism by the scientific community after Prof. Jeffries Wyman correctly identified it as the hodgepodge of whale bones it was. This lead to a lot of jokes about Prof. Silliman being a silly man, to the point where he asked Koch to take his name off the thing. Koch subsequently renamed the species to ''H. harlani''. Being dead by this point, Dr. Harlan was unable to decline the dubious honour.

''Basilosaurus'' with its size was arguably the top predator of its oceans, potentially preying on every other creature of its world — like mosasaurs, plesiosaurs, and ichthyosaurs did in the Dinosaur Era, and like the armored fish ''Dunkleosteus'' did before dinosaurs evolved. However, it may have been a less able swimmer than modern cetaceans because of its primitiveness, maybe more similar in swimming style to a pinniped (seal, sea-lion etc.) than to a modern whale. Since soft remains have not been preserved, we don't know if the basilosaur's tail fluke was already identical to modern whales/dolphins, or smaller and/or shaped differently, nor if it had a dorsal fin. Unlike modern whales, it retained the tiny remnants of its hindlegs (which were maybe used to lock mating pairs' bodies together), as shown in its fossils.

''Basilosaurus'' has been a recent hit in documentary media since the 1990s and especially the 2000s; see ''Series/WalkingWithBeasts'' for an example. But it hasn't received the same amount of attention in broader popular culture as other giant sea critters of the past (''[[StockNessMonster Elasmosaurus]]'', megalodon, ''[[Film/JurassicWorld Mosasaurus]]''). In 2001's ''Series/WalkingWithBeasts'' it's shown initially throwing a shark in the air like modern orcas do often with sea-lions, but then is shown struggling for survival in the empty-of-prey seas it swam in. In 2003's ''Series/SeaMonsters'', it's depicted with the same appearance as in the former, as the fourth most dangerous sea predator of prehistory after the megashark ''Carcharocles megalodon'' and two stock sea reptiles, the "giant mosasaur" and the famously oversized ''Liopleurodon''. Note that the more modern whale ''Livyatan'' was not yet discovered when the program was broadcast (it was found only in TheNewTens); this explains its absence in the show despite being even more powerful in RealLife than ''Basilosaurus'', as it's thought to have hunted large baleen whales (see below).

# '''TropeMaker:''' Walking with Beasts

!! Giant Skull: ''[[http://en.wikipedia.org/wiki/Andrewsarchus Andrewsarchus]]'' *

''Andrewsarchus'' (''not'' "Andrewsaurus") means "Andrews' ruler" and is one of the most enigmatic mammals, from the first part of the Cenozoic (the Eocene period) like the dinocerates and the brontotheres. As its complete name suggests (''Andrewsarchus mongoliensis'') it was discovered [[ExactlyWhatItSaysOnTheTin in Mongolia]], during the same American expedition led by Roy Chapman Andrews ([[NamedAfterSomebodyFamous hence the name]]) in which ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Velociraptor]]'' was first found.

Only one single skull is known, about 1m/3ft long and vaguely wolf-like. ''Andrewsarchus'' has classically been called the largest carnivorous land mammal ever (it could have been nicknamed "[[{{Badass}} Badassotherium]]" for this). But there isn't any hard proof of that; it might have been omnivorous instead, and of course its overall size can only be guesstimated. It is often depicted as a scavenger of large herbivores' carcasses, but has also been shown as an active hunter. ''Andrewsarchus'' was traditionally considered to be closely related to the much smaller [[UsefulNotes/PrehistoricLifeMammals Mesonychids]], and depicted with small hooves on its feet like the latter. However, [[http://scienceblogs.com/tetrapodzoology/2009/08/mesonychians_part_iii_andrewsa.php later]] [[http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0007062 phylogenetic studies]] indicate that it might have actually been a close relative of the Entelodonts (large even-toed ungulates resembling boars in shape), though obviously any phylogenetic placement is only tentative at this point.

In ''Series/WalkingWithBeasts'', ''Andrewsarchus'' is shown with the overall shape and color of a gigantic [[http://en.wikipedia.org/wiki/Civettictis_civetta civet]] (a small African carnivore), and crushing with its jaws a sea turtle that was crawling on the beach to return to the sea after having laid its eggs, but obviously this is another invention of the show without paleontological proof. According to modern hypotheses, the real ''Andrewsarchus'' was also smaller than it appears in the show, as giant basal land mammals usually tend to have big heads compared with the rest of the body.

How did elephants look when they were just starting to evolve? Not really like pachyderms. The most classic ur-elephant is ''Moeritherium'', found in Egypt in the Eocene period. It's been called "the first elephant", but some proboscideans were even more basal: ex. the fox-sized ''[[http://en.wikipedia.org/wiki/Eritherium Eritherium]]'' (''Moeritherium'' without the "''Mo-''") is the most ancient proboscidean currently known, from Paleocene Africa.

The medium-sized barytheres and numidotheres, and even the giant Deinotheres above, are all just as basal as ''Moeritherium''. All these primitive proboscideans shared multiple cheek-teeth in their jaws like a typical mammal, not only one single giant cheek-tooth for each half-jaw like the evolved modern elephants and mammoths, or the almost-elephant stegodonts.

Unlike the deceptively elephantine deinotheres, ''Moeritherium'' ("Lake Moeri's beast") didn't resemble much an elephant. No bigger than a large pig, it had four short tusks, a pair in the upper jaws and another in the lower ones like in the more elephant-like "mastodonts". It had also hippo- or tapir- like limbs and possibly pig-like or tapir-like snout (unlike ''Macrauchenia''), and was definitively more like a tapir than an elephant in appearance. Living in a mixed aquatic-terrestrial habitat, the moerithere is often thought to have been an amphibious animal a bit like a modern hippopotamus or a tapir, but its actual lifestyle is still unknown. In ''Series/WalkingWithBeasts'' it's shown as a potential prey for the giant early whale ''Basilosaurus'', which however fails in its attack.

''Moeritherium'' lived alongside the much bigger horned herbivore ''Arsinoitherium'' in the same habitat. Like the ur-horse ''Eohippus'', ''Moeritherium'' has often been shown in textbooks as the start of the evolutionary trip of its group, the [[http://en.wikipedia.org/wiki/Proboscidea Proboscidea]], passing through deinotheres, mastodonts, gomphotheres, stegodonts etc. and ending with modern elephants and mammoths. Its look tends to vary a bit in classic paleo-art: some depict ''Moeritherium'' as a sort of boar-thing with dense hair, while others show it naked-skinned and more looking like a hippopotamus, and usually but not always with an elephant-like short trunk and the four short tusks.

Together with ''Andrewsarchus'' this has always been one of the most enigmatic prehistoric giant mammals, despite (unlike ''Andrewsarchus'') being known from complete skeletons. It wasn't a true elephant relative like ''Moeritherium'', being outside the order Proboscidea, but was perhaps the most peculiar, and at the same time one of the most striking-looking, among the prehistoric "pseudo-rhinos".

''Arsinoitherium'' means "Arsinoe's beast": Arsinoe was an [[AncientEgypt ancient Egyptian]] queen, and some could rename the animal "the Pharaoh's Megahorn". It is sometimes misspelled "Arsinotherium" without the "i" in the middle because so it's [[TheUnpronounceable easier to pronounce]]. ''Arsinoitherium'' lived in the Eocene epoch, a bit later than ''Uintatherium'' but earlier than the brontotheres, and was of similar size and body shape to the former. Once, both ''Uintatherium'' and ''Arsinoitherium'' were placed in the same mammalian order, the "Amblypods" ("short foot") together with the lesser-known Pantodonts, but ScienceMarchesOn and recent research says otherwise: ''Arsinoitherium'' was an [[http://en.wikipedia.org/wiki/Afrotheria Afrothere]] like elephants (though not one of their ancestors), while the uintatherians and the pantodontians were probably [[http://en.wikipedia.org/wiki/Laurasiatheria Laurasiatheres]], closer to true ungulates but also to carnivorans, pangolins, and bats (and, more distantly, to rodents and primates).

''Arsinoitherium'''s most visible peculiarity is by far its huge, yet lightweight, hollow "quadruple-horn", which rivals in size and oddity the crests of the [[UsefulNotes/StockDinosaursOrnithischianDinosaurs hadrosaurian dinosaurs]] (which were often also hollow) or the frills of the ceratopsians. But this thing was sometimes even asymmetrical like caribou antlers, with one main branch longer than the other: for some, it's a bit similar to a cross between a brontothere's forked horn and a Irish elk's antler. Like the ''Parasaurolophus'' crest, the exact purpose of this huge headgear has been a headache for experts. Defense? Courtship device? Or even ''thermoregulation''? We don't even know if only males had it.

The same size as modern rhinos and hippos, this animal has often been also described as [[MixAndMatchCritter a cross between the two]], because of its short robust legs ending with "hooflets", and probably amphibious habits. Indeed, the arsinoithere lived along the coasts bordering the shallow seas which covered what's now Egypt together with the ur-elephant ''Moeritherium'' (possibly amphibious as well), and probably ate both land vegetation and sea plants.

Both ''Arsinoitherium'' and ''Moeritherium'' were portrayed in the ''Franchise/WalkingWith'' series (though in different spinoffs), in the episodes in which the predatory whale ''Basilosaurus'' is the main character. In the show, ''Arsinoitherium'' is shown with a short trunk like a tapir, and thus looking like simply a bigger, horned version of the ''Moeritherium'', but the trunk is improbable, because the shape of the nasal opening of the skull doesn't show points of attachment for a trunk, even a small one. We don't know if it was naked-bodied or hairy-bodied.

Finally, let's mention a lesser-known arsinoitherian peculiarity: its teeth were more numerous than most four-legged mammals (though similar to cetaceans), and not clearly differentiated into incisors, canines, and molars. This mammal is so strange that it is placed in its own mammalian order: the Embrithopods, fairly close to proboscideans, sirenians, hyraxes, and the extinct Desmostylians (below).

# '''TropeMaker:''' Its "horn"

It's worth noting that mammoths, scientifically speaking, were just another genus of elephant, since they belonged to the same family, Elephantidae. The Asian elephant (''Elephas maximus'') is slightly more closely related to mammoths (''Mammuthus'') than to its more distant modern African relatives (''Loxodonta africana'' and ''Loxodonta cyclotis'') -- thus mammoths (and mastodons) ''weren't'' the direct ancestors of elephants as is sometimes claimed. Also within Elephantidae was ''Palaeoloxodon'', the "straight-tusked elephant"; the best-known species of which is ''[[http://en.wikipedia.org/wiki/Palaeoloxodon_antiquus Palaeoloxodon antiquus]]''. Formerly believed to be related to Asian elephants, its now considered to be closer to African elephants. It also lived during the Ice Age, but it preferred warmer climates and was bigger than the woolly mammoth at about the same size as the Columbian mammoth. Other recently-extinct elephantids underwent a high degree of insular dwarfism, some becoming as small as an average sheep or pig.

Not all fossil mammals that looked like rhinoceroses actually were, although they'll probably get identified as such in popular media. Among the most well-known is ''Uintatherium'' ("Uinta Mountains' beast"), found in huge numbers in several fossil deposits in the western USA (but also in China). Like several other early mammals, it was described for the first time during the Bone Wars — Marsh called it "''Dinoceras''", "terrible horn", but the animal was re-designated ''Uintatherium'' by Joseph Leidy. For some, however, it recalls more a hippo than a rhino because of its upper pair of tusks, to the point it could be renamed "[[MixAndMatchCritter the saber-toothed rhinoceros]]" or the "[[MixAndMatchCritter six-horned hippopotamus]]".

The uintathere is perhaps the most mistreated extinct mammal of them all. Expect somebody describing its appearance as [[PrehistoricMonster "monstrous" or "scary"]]. True, it had three pairs of giraffe-like "horns" and the two aforementioned upper protruding tusks, but, honestly, if ''Uintatherium'' were alive today, it would probably appear no scarier than an elephant, rhino, hippo or giraffe. Also expect a crack about its allegedly slow movement and its "tiny" brain (just like what happens to ''[[DumbDinos Stegosaurus]]''), and just like the stegosaur, expect the writer to cite [[TooDumbToLive its slowness and/or stupidity as the reason for its extinction]]. Though they had comparatively short limbs and feet, similar in shape to an elephant's, this wouldn't necessarily have prevented uintatheres from running with speed if necessary — again, just like modern elephants, or rhinos, or hippos.

In RealLife, uintatheres were among the very first mammals to reach large sizes (about as large as a modern-day rhino), and their body plan was ''very'' successful at the time, as they roamed the northern hemisphere in huge numbers for millions of years in the early Cenozoic (in [[https://en.wikipedia.org/wiki/Eocene the Eocene epoch]], to be precise), before being outcompeted by the even larger brontotheres and the first true rhinos. Uintatheres are usually depicted with rhino-like hide and sideways-pointing ears, a bit like a cow; sadly, we don't have remains of soft tissues from them, so we don't know how their skin and ears really looked. We're not sure if their six "horns" were covered in skin like a giraffe, or keratin like cattle or antelopes, either. Another known genus of uintatheres was the almost-identical ''[[http://en.wikipedia.org/wiki/Eobasileus Eobasileus]]'' ("dawn king"), about of the same epoch.

Rather strangely, the famous franchise ''Franchise/WalkingWith'' doesn't mention uintatheres in any of its pieces, despite them having been among the most iconic early big herbivores in the Mammal Age. This could be seen as a missed opportunity to talk more accurately about these animals, also because uintatheres are scientifically better-understood than many other kinds of mammals from the Eocene epoch. In more mainstream media, on the rare occasions they appear, they are frequently mislabeled "prehistoric rhinos" or even [[ArtisticLicensePaleontology ceratopsids]].

!! Slingshot Horn: ''[[http://en.wikipedia.org/wiki/Megacerops Megacerops]]'', aka "Brontotherium" **

''Megacerops'' (formerly called ''Brontotherium''... these ''[[UsefulNotes/StockDinosaursTrueDinosaurs Bronto]]''s just can't keep their names) is the prototype and the most well-known member of its group of mammals, the [[ExactlyWhatItSaysOnTheTin Brontotheres]], ("thunder beasts"), also called Titanotheres ("titanic beasts"). However, one brontothere, the primitive ''Brontops'', maintained its bronto- prefix... until it was reclassified as a synonym for ''Megacerops''.

While ''Uintatherium'' was not related to any modern hoofed mammals (belonging to the extinct mammalian order called Dinocerata), brontotheres were [[http://en.wikipedia.org/wiki/Perissodactyla Perissodactyls]] (odd-toed ungulates), thus distant relatives of horses, tapirs, and rhinos. The biggest brontotheres were almost ''Triceratops''- or elephant-sized (larger than the biggest uintatheres), but still smaller than other giant herbivorous mammals of prehistory, like the giant mammoths and the guy we'll see in the next chapter.

Also first discovered during the Bone Wars (this time by Cope, and also officially described by Leidy with the older classical name "Brontotherium"), ''Megacerops'' had a more rhino-like appearance than the uintatheres, having one single "horn" on its nose, and no tusks. Unlike rhinos, however, brontotheres' protrusion was bony and not made of hardened hair, and thus its shape has preserved in fossils, unlike the latter. The horn of the North American ''Megacerops'' was forked with round points (rather slingshot-like), while that of its Asian cousin ''[[http://en.wikipedia.org/wiki/Embolotherium Embolotherium]]'' (the brontothere portrayed in ''Series/WalkingWithBeasts'', as a protective mother toward its dead calf) was shovel-like and not forked. Both had notably concave heads if seen from the side, with the eyes rather near the top, and also a big hump on their shoulders like a bison. If their "horns" (better, cranial bony appendages) were covered in hairy skin, naked skin, or in keratin is uncertain -- the same about the appendages of the uintatheres. Brontotherians had four digits on the front feet and three on the back, like the ur-horse ''Eohippus'' and modern tapirs (true rhinos always have three toes on each foot). Like uintatheres, we don't know if brontotheres were hairy-bodied like bovines or "naked" and "armor-skinned" like typical rhinos or hippos.

Like uintatherians, brontotherians roamed plains of the northern continents in huge numbers in the Early Cenozoic; compared with uintatheres, they tend to be portrayed as more active and faster-running in paleo-art, and more overall similar to true rhinos, but still rather unintelligent because of their smaller brains. Note, however, that small brains ''don't'' necessarily mean low intelligence; after all, dinosaurs are today well-known to have been intelligent and social creatures despite having even smaller brains than those of the brontotheres and uintatheres.

Brontotheres eventually went extinct perhaps because they weren't able to adapt to the diffusion of the first grasslands, which replaced their former food sources (scrub and non-grass herbs). Like uintatheres, expect to see brontotheres identified as rhinoceroses or ceratopsians in popular works. Despite this, it seems that their closest living relatives among odd-toed ungulates were the equids (horses and their kin), and not the rhinoceroses!

Two brontotheres appear prominently in the WesternAnimation/IceAge film: according to their appearance, they are ''Megacerops'' and ''Embolotherium''. They fall in the RhinoRampage trope.

Here is Our Majesty, the "biggest land mammal that ever lived"; though some [[ScienceMarchesOn recent research]] indicates that some giant mammoths like the Steppe Mammoth (''M. trogontherii'') and, even more recently, the Asian straight-tusked elephant ''[[http://en.wikipedia.org/wiki/Palaeoloxodon_namadicus Palaeoloxodon namadicus]]'' were heavier, neither were as long or tall as ''Paraceratherium''. See [[https://en.m.wikipedia.org/wiki/Largest_prehistoric_animals here]] to have an idea about the current knowledge about prehistoric creatures' size.

Its size was really ''immense''; it would make modern pachyderms look small in comparison. The paracerathere was 5m up to the shoulders, as tall as a ''Brontosaurus''; reached 7.5m/24ft when holding its head high, 5ft taller than the tallest giraffe; and weighed 15 tons, as much as ''three'' elephants or three ''T. rex''es (some earlier estimates made it even heavier than that: up to 30 tons, as much as a brontosaur!). Contrasting with all this, it had a quite slender, elegant frame: a sort of muscular giraffe with a long straight neck, small hornless head, and long, slender limbs with three hoofs each, like a rhino — indeed, it was a close rhino relative. Its behavior was probably more giraffe-like than elephant- or rhinoceros-like, browsing the tree tops and walking with long steps like a giraffe. In short, it was the mammalian equivalent to a sauropod.

It lived in Oligocene, in the middle of the Cenozoic, later than brontotheres and uintatheres, and was only the biggest member of a whole group of extinct "rhinos" (or rather, rhino relatives): the hyracodontids, most of which were horse-sized and more similar to horses than to rhinoceroses. Our record-holder is also a prime example of IHaveManyNames among prehistoric critters: now called ''Paraceratherium'' ("near-horned beast"), its traditional names are ''Indricotherium'' ("Indrik's beast") and ''Baluchitherium''. This last name is the oldest, and most frequent in older books: it means "beast from Baluchistan" because was originally found in this Asian region, straddling Pakistan and Iran. There are still some scientists that believe they are three distinct yet similar genera of animals, like the equally controversial ''Brontosaurus'' and ''Apatosaurus'' case.

Some think these critters went extinct because became actually ''too'' large, and when their habitat dried out, they were unable to find sufficient food; but this is only a supposition. It's also speculated that they're at or near the upper limit for how big a land mammal can get; no evidence of a land mammal larger than 20-30 tons has ever been found. There's much speculation as to ''why'' this would be the upper limit, though the very long gestation periods[[note]]a modern elephant's pregnancy lasts almost 2 years, and it's believed that both ''Paraceratherium'' and the largest of the mammoths probably took even longer to give birth[[/note]] are suspected to be a major factor. This results in low birth rates that make it more difficult for huge mammals to recover from any major population loss. Anyway, like brontotheres and uintatheres, indrico/paracera/baluchitheres were well adapted to their environment and were successful animals, though relatively short-living compared with other lineages of mammals like the true horned rhinoceroses that have reached our days with five species.

A young "indricothere" is the main character of the third episode of ''Series/WalkingWithBeasts''. To indirectly illustrate how big the adults of its species are, the beginning of the episode shows its mother defending it just after it's born against a pack of ''Hyaenodon''s (see below), the latter being described as "as big as rhinos" but still appearing tiny next to the adult indricothere. Indricotheres also appear huge confronted with the neighboring chalicotheres and entelodonts, even though both mammals were taller than a human and weighing more than one metric ton; at the end of the episode the grown but still young indricothere is bigger than the ''adult'' entelodont, and easily chases it away from the scrubs nearby.

Let's return to extinct elephant relatives... there were A LOT of them in prehistory, not only woolly mammoths and American mastodons. Many of them were even cooler-looking than those two, though all (except the most primitive, such as ''Moeritherium'' below) shared a similar shape to a modern elephant, with long pillar-like limbs, short feet with round nails, short necks, small tails, and compact bodies. It was their mouths and teeth that were ''very'' different.

''[[http://en.wikipedia.org/wiki/Gomphotherium Gomphotherium]]'', for example, resembled a cross between an elephant and a hippo, with its shovel-like lower jaws; ''Platybelodon'' was similar but took this to an extreme, with a huge mouth opening. Both belonged to the subgroup of proboscideans called the [[http://en.wikipedia.org/wiki/Gomphothere Gomphotheres]], whose ''Platybelodon'' is the [[RuleOfCool most commonly-shown member]] in media. Smaller than modern elephants, these animals were once classified within the "mastodons" as said above, but the latter has been found to be an artificial assemblage of archaic proboscideans, only united by one thing: they had a pair of tusks ''both'' in the upper jaw ''and'' in the lower. In ''Platybelodon'', ''[[http://en.wikipedia.org/wiki/Palaeomastodon Palaeomastodon]]'', ''Gomphotherium'', ''[[http://en.wikipedia.org/wiki/Phiomia Phiomia]]'', and other "gomphotheres" (or similar forms), the upper ones were small and normal-looking; the lower tusks were placed on the tip of the jaw, and were flat and very untusk-like, possibly used to "gather" ground-level vegetation like a literal shovel. One gomphotherian, ''[[http://en.wikipedia.org/wiki/Amebelodon Amebelodon]]'', had especially long "shovels" on a relatively short mandible; others, like ''[[http://en.wikipedia.org/wiki/Stegotetrabelodon Stegotetrabelodon]]'', had very long and more pointy lower tusks, literally resembling a four-tusked elephant. Some gomphotheres, like ''Cuvieronius'', ''Notiomastodon'', and ''Stegomastodon'', reached South America, the only proboscideans that managed to do that.

Gomphotheres are often shown with bizarre ''flat'' trunks to accommodate the shape of the lower jaw, but this is actually unproven — trunks have no bones, so they didn't fossilize. However, recent studies suggest gomphotheres had normal cylindrical elephant-like trunks instead, as the tusks show signs of wear suggesting the animals were browsers as opposed to feeding on water plants as previously suggested. Interestingly, ''Literature/TheLordOfTheRings''' Mûmakil were shown in TheFilmOfTheBook with a pair of [[https://youtu.be/uRgIja3K1ac gomphothere-like lower tusks]].

Other "mastodonts" were more similar to elephants, but even they would appear unusual to modern eyes: ''Anancus arvernensis'' (the second word means "from Alvernia", the French region where it was first-found), is nicknamed the "European mastodon" because with its straight, spear-like upper tusks (while the lower ones were almost missing) and relatively short limbs, was very similar in size and shape to the much more primitive American mastodon (''Mammut americanum''), but with much bigger tusks than it. It lived during the Ice Ages like the latter but in Europe instead of North America, and its fossils are found further south than those of the European specimens of woolly mammoths.

''Anancus'', unlike ''Mammut'', was one of the closest relatives of the proper elephants, the [[http://en.wikipedia.org/wiki/Elephantidae Elephantids]], according to most experts, and had some relatives, like ''[[http://en.wikipedia.org/wiki/Tetralophodon Tetralophodon]]''; but even closer, forming the sister clade outside the elephant-mammoth group, were the [[http://en.wikipedia.org/wiki/Stegodontidae stegodonts]] ("roof-tooth"). They were basically true elephants, only with more primitive cheek-teeth and some other different details, and lived in Africa and Asia until a few thousand years ago, in full Ice Age. Among them, the Indian ''Stegodon ganesa'' (named after the elephantine deity [[Myth/HinduMythology Ganesha]]) had huge parallel tusks so close to each other that illustrations show the animal as obligated to keep its trunks ''to the side'' of both tusks! The first and most primitive true Elephantid genus was ''[[http://en.wikipedia.org/wiki/Primelephas Primelephas]]'' ("first elephant"), still similar to a gomphothere by having well-developed lower tusks, which got completely lost in the four more classic elephantid genera: ''Loxodonta'' (the modern African elephants), ''Elephas'' (the modern Asian elephants), ''Palaeoloxodon'' (the extinct straight-tusked elephants), and ''Mammuthus'' (the true mammoths).

A more primitive proboscidean lineage includes the genus ''Deinotherium'' ("terrible beast"). Unlike the mastodonts and gomphotheres, deinotheres had only two tusks like modern pachyderms, only they grew from the ''lower'' jaw like a two-pronged fork, and were curved downward. The function of these tusks is still uncertain: possibly stripping the bark from trees, or fighting against individuals of the same species.

Deinotheres lived throughout the Cenozoic era, and some managed to survive long enough to meet our first human ancestors in Africa. They had longer limbs than mastodonts and gomphotheres, and much longer than the basal ''Moeritherium'', and some were taller at the shoulders than to the hips, like a giraffe. Their tail was small, and apart from their head they looked like true elephants despite their extreme primitiveness among proboscideans - a great case of Parallel Evolution with the other giant proboscideans.

Some Asian deinotheres were as big as the aforementioned giant mammoths: the largest one (''Deinotherium giganteum'') lived before the appearance of the australopithecines. This one is shown in ''Series/WalkingWithBeasts'', [[RuleOfCool wrongly placed]] [[MisplacedWildlife in Pliocenic Africa]], [[BiggerIsBetter oversized]] (described "as tall as a giraffe but 14 times heavier") and portrayed as a serious hazard for ''[[UsefulNotes/PrehistoricLifeMammals Australopithecus]]''. Here a sexually-excited male [[BarbaricBully tries to kill]] every "ape-man" he encounters like modern male elephants often do while in [[https://en.wikipedia.org/wiki/Musth musth]]. But this behavior is merely speculative, and since deinotheres were among the most distant elephant relatives among proboscideans (in the past, some didn't even consider them related to elephants at all!), this may be unlikely. The African deinotheres were actually never bigger than a modern Asian elephant.

Like mastodons and gomphotheres, we don't know how deinotheres' trunks or ears were shaped, but probably the trunk was cylindrical and as long as those of modern elephants (again, unlike what appears in ''WWB''). Of course, we don't know for sure if ancient proboscideans could trumpet like modern elephants do. It's highly probable that at least true mammoths (and the strictly-related palaeoloxodonts) did trumpet, since they were extremely closely-related to modern elephants. Similarly, we don't know how much hair extinct proboscideans had on their bodies (if any); woolly mammoths and American mastodons of the genus ''Mammut'' are exceptions only because they have preserved soft tissue other than bones.

''Andrewsarchus'' (''not'' "Andrewsaurus") means "Andrews' ruler" and is one of the most enigmatic mammals, from the first part of the Cenozoic (the Eocene period) like the uintatheres and the brontotheres. As its complete name suggests (''Andrewsarchus mongoliensis'') it was discovered [[ExactlyWhatItSaysOnTheTin in Mongolia]], during the same American expedition led by Roy Chapman Andrews ([[NamedAfterSomebodyFamous hence the name]]) in which ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Velociraptor]]'' was first found.

''Coryphodon'' was one of the biggest mammals of the Eocene, the size of a large cattle (but still smaller than ''Uintatherium'', the brontotheres, and ''Arsinoitherium'') and lived roughly alongside the famous bird ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Gastornis]]''. It was very similar to a hornless uintathere, with small tusk-like canines like the latter, is classically compared with a hippo, and was once classified together with uintatheres in the same order of mammals, the "amblypods"; today ''Coryphodon'' is considered a highly derived member of the Pantodonts (the first large, plant-eating land mammals), whose was one of the biggest members. Though smaller than other later herbivorous mammals, as an adult the coryphodont probably feared no predators except for perhaps some giant reptiles (crocodilians, constrictor snakes). Classic portraits often show the coryphodont amphibious like a hippopotamus, but it could have been more terrestrial. It was often believed slow and had actually a very small brain, but again, this doesn't mean it was harmless and/or witless.

It's not common to see prehistoric rodents and other usually small-sized mammalian groups, like rabbits, bats, "insectivorans"[[note]]moles, hedgehogs, and shrews; properly called eulipotyphlans[[/note]], or pangolins, in popular media. However, these guys tend to be a bit more commonly-seen than the others.

Now we'll go before the Ice Ages and meet the so-called "horse ancestors" (more precisely, the equid ancestors). Even though little-portrayed in more mainstream media, they are more familiar than other pre-Ice Age mammals because they have always been among the symbols of evolution, almost as much as the [[UsefulNotes/StockDinosaursSaurischianDinosaurs dodo]] is the icon of extinction. Horse ancestors weren't so cool-looking compared to most other extinct hoofed mammals: they mostly resembled their modern namesake at a glance. The most famous of these [[{{Pun}} forerunners]] are, obviously, the [[RuleOfCool least horse-like]] of them all, at least averting BiggerIsBetter for once, as they were also the smallest: ''Eohippus'' ("dawn horse") and ''Hyracotherium'' ("mole beast"), often considered the same animal in the past.

An almost-unbelievable ScienceMarchesOn affair has actually encircled horses' evolution, despite its iconic role in popular science. This evolution was ''not'' as linear as shown in popular science books and elsewhere, though it's certain that equine ancestors progressively lost their digits from four or three to one for each foot, their heads became loftier to see farther, their limbs became nimbler to run faster, their overall size constantly increased, and their teeth progressively adapted from browsing forest vegetation to grazing the grass of the first grasslands to appear in the Miocene epoch (middle Cenozoic). Horse evolution has often been cited as a symbol of progress and improvement in general, probably due to the historical fame of the horse as a "noble" animal, that started as a small modest forest-dwelling leaf-eater... forgetting that modern animals are actually not "better" than the older ones ''only'' because they [[HumansAreSpecial reached our time]]; every animal is adapted to the environment of its own period. Elephants too and their evolution have had a similar reputation of the horses' one in pop-science media, and elephants have also been classically quoted as "noble" animals in several human cultures.

Of course, expect to see the small, basal ungulates ''Hyracotherium'' and ''Eohippus'' called "horses" anyway, despite their possibly having nothing more in common with horses than with tapirs or rhinos (the other living odd-toed ungulates); moreover, the "Hyracotherium-Eohippus" stew has included several other early ungulates, some of which ''were'' horse ancestors and some of which weren't. Sadly, systematics of the earliest ungulates is still a total mess. Among modern ungulates, the artiodactylan Tragulids or musk-deer and the Duiker antelopes are perhaps the ones that resemble these animals the most in size and appearance.

Whenever the putative "ur-horse" ''Hyracotherium''/''Eohippus'' shows up in media, expect it to be portrayed as a RedShirt, usually falling prey to the giant flightless bird ''Gastornis''/"Diatryma". Now that [[ScienceMarchesOn science has marched on]], we know it's highly unlikely for the bird to have any interests in the small ungulates due to its probably herbivorous diet — though the "ur-horses" might nonetheless have been prey for other animals of the time, being "[[StockPhrase as large as a fox terrier]]", to use a classic description in paleo-books. Among fictional appearances, the most notable was perhaps Creator/RayHarryhausen's cowboys-versus-dinosaurs film ''Film/TheValleyOfGwangi''.

!! A Run for the Future: the [[http://en.wikipedia.org/wiki/Horse_evolution Horse Ancestors]] *

Among confirmed horse ancestors, they make a sort of {{pun}} if read together. ''[[http://en.wikipedia.org/wiki/Mesohippus Mesohippus]]'' ("middle horse"), still small and with three fingers for each limb, was still a forest browser like ''Eohippus''; ''[[http://en.wikipedia.org/wiki/Merychippus Merychippus]]'' ("grazing horse"), also with three digits, was larger, more horse-like and [[ExactlyWhatItSaysOnTheTin grazed]] Miocene grasslands; ''[[http://en.wikipedia.org/wiki/Pliohippus Pliohippus]]'' ("more horse") was very similar to a modern equine in size and shape, and had the familiar one-hoofed toe. They are the most commonly-shown in media, but there were in reality dozens of other ''-hippus'', almost all of them North American. Also worthy of note, however, are ''[[http://en.wikipedia.org/wiki/Hipparion Hipparion]]'' (meaning "pony" in Greek) and ''[[http://en.wikipedia.org/wiki/Hippidion Hippidion]]'' (lit. "little horse"), which break the theme of having ''-hippus'' as prefix instead of suffix; they also break the geographic rule, the first being an Old World critter, the second South American, both offshoots of the horse tree which didn't leave any descendants. Remember that ''all'' modern equines descended from North American ancestors. Funnily enough, the mustangs or "wild horses" of North America are actually descendants of European domesticated horses, which are descended from true wild horses (''Equus ferus'') of Asia and Europe — which, in turn, originated from North American ancestors. There were also a few exceptions of the "''-hippus''" rule, such as ''[[http://en.wikipedia.org/wiki/Anchitherium Anchitherium]]'' (another Eurasian offshoot but earlier than ''Hipparion'' or ''Hippidion'': the latest two survived almost until today).

Oh, and: all the animals above were not only the horse's ancestors, but also the donkey's and zebra's — and also the lesser-known wild asses of Africa and Asia. Also note that despite their different appearances and habits, modern equids are so closely related to each other they're all placed in a single genus, ''[[http://en.wikipedia.org/wiki/Equus_(genus) Equus]]'' — while, by comparison, the modern five rhinoceros species are put in ''four'' different genera despite being all called "rhinos" in common speech: ''Diceros'' (the black rhino), ''Ceratotherium'' (the white rhino), ''Dicerorhinus'' (the Sumatran rhino), and the namesake ''Rhinoceros'' (both Indian and Javan rhinos). The genus ''Equus'' also includes two recent historical extinctions: the African quagga, a kind of zebra with incomplete stripes, and the European tarpan, the direct ancestor of the domestic horse. See below for them.

Unlike ''Eohippus'' and kin, all these confirmed horse ancestors like ''Mesohippus'', ''Merychippus'', ''Pliohippus'', ''Hipparion'', and ''Hippidion'' have little chance of ever appearing in non-documentary media, probably because they look more like modern horses.

The most commonly portrayed species of mammoth is by far ''Mammuthus primigenius'' (lit. "primeval mammoth"), better known as the woolly mammoth, or THE mammoth ''par excellence''. It is probably the most iconic non-dino prehistoric animal of all, thanks to its resemblance to an elephant with huge curly tusks and dense hair, but also to the countless, extraordinarily well-preserved specimens with soft tissues found in northern Eurasia and northern Alaska and Canada. These findings have long made it one of the most accurately-portrayed of all prehistoric animals, and one of the very rare extinct animals almost as scientifically well-known as a still-living animal. However, the real cause of its extinction [[WildMassGuessing remains unclear]], as is [[WildMassGuessing the precise meaning]] of the word "mammoth", which is of Russian origin. The most common theory is that it derives from a Native Siberian word for "earth", as frozen carcasses emerging from the permafrost were mistaken for huge burrowing beasts. "Mammoth" as an adjective derives from the extinct animal -- the first person to use it that way was US President UsefulNotes/ThomasJefferson (for a wheel of cheese, no less!), who had a major interest in paleontology.

Some people use -- or even applying the term to other extinct proboscideans

Moving on to a lighter topic (and way before the Ice Age), we head to the then-island continent of South America, ruled by a strange cast of apex predators -- [[UsefulNotes/StockDinosaursSaurischianDinosaurs terror birds]], [[UsefulNotes/PehistoricLifeNonDinosaurianReptiles terrestrial crocodile-relatives]], and the next guys on our prehistoric tour, the sparassodonts. Though not "marsupials" in the modern sense of the term, and thus possibly lacking a true "pouch" just like some South American opossums, the sparassodonts were a closely related lineage of carnivorous mammals that converged on many placental carnivorans. Members included the bear-like ''Borhyaena'' and the weasel-like ''Cladosictis'', but the largest and most well-known of these was the Miocene-Pliocene ''Thylacosmilus atrox'' ("atrocious pouched knife"), a marsupial ''sabertooth''.

# '''TropeMaker:''' Their resemblance with big cats

!! A Cold Safari: the [[http://en.wikipedia.org/wiki/Panthera_spelaea Cave Lion]] & the [[http://en.wikipedia.org/wiki/Panthera_atrox American Lion]] *

True prehistoric cats weren't all sabertooths; there were also more normal-looking ones, which make up the subfamily Felinae (Felis = "cat" in Latin), while sabertooths comprise the Machairodontinae. The former are nicknamed by paleontologists "biting cats", the latter "stabbing cats"; it's easy to see why.

The most well-known "biting" extinct cats were the American lion (''Panthera atrox'': ''atrox'' = "atrocious") and its Eurasian cousin, the cave lion (''Panthera spelaea'': ''spelaea'' = "from caves"), both often considered simply larger, Ice Age subspecies of the modern lion (''Panthera leo''), and well-adapted to live in colder climates along with the northern species of mammoths. Some think they were the main predators of ancient humans, but this is not certain. They were similar in shape and look to modern ''Panthera'' felines, but unlike modern lions - at least according to some prehistoric paintings - they had no manes. It's uncertain if their social structure was identical to modern lions, or if they were more solitary like tigers and jaguars.

In ''Series/WalkingWithBeasts'' a cave lion has a minor role in the episode dedicated to the woolly mammoths: here it's correctly depicted mane-less unlike in other paleo-artistic works, and living in small prides... but with an odd snow-white color to its fur, and even small "sabers" like a "stabbing cat", being a reused model of the ''[[UsefulNotes/PrehistoricLifeMammals Dinofelis]]'' of the 4th episode which ''was'' an actual short-sabered sabertooth cat; actually the cave lion's teeth were identical to those of every other "biting cat", and its coloration was likely brownish, like a modern lion but paler.

The [[http://en.wikipedia.org/wiki/Cave_Hyena Cave Hyena]] is regarded today as a simple subspecies (''Crocuta crocuta spelaea'') of the well-known African spotted hyena (''Crocuta crocuta''). The cave hyena lived alongside the cave lion in Ice Age Eurasia, but compared with the more famous cave bear both were less strictly associated with caves. The Ice Age hyena was arguably similar in appearance and behavior to its Savannah equivalent, but with thicker fur against the cold. However, in ''Prehistoric Park'' cave hyenas are not CGI but live-acted by modern spotted hyenas, and we don't know if in reality cave hyenas "laughed" exactly like an African spotted hyena despite being very closely related.

There were indeed ''many'' mammoth species in RealLife, and as a group they lived throughout most of the Ice Ages. The largest ones did challenge ''Paraceratherium'' for the title of largest land mammal ever, weighing 15 tons or more (comparable to a medium sauropod dinosaur), while a modern elephant and a woolly mammoth are "only" 4-6 tons (like a big ceratopsid or stegosaur). However, a paracerathere would still be taller than every mammoth thanks to its giraffe-like shape.

The most famous are the American Columbian mammoth (''Mammuthus columbi'' — an older more classic synonym is Imperial mammoth, ''Mammuthus imperator'') and the lesser-known but even larger Asian Steppe mammoth (''Mammuthus trogontherii'' - an older synonym is ''Mammuthus sungari'', which was actually only a particularly big specimen of ''trogontherii''), very similar to each other in look, and both with the typical dome-like head and hump on their shoulders shared with the woolly mammoth. Other members include ''[[http://en.wikipedia.org/wiki/Mammuthus_meridionalis Mammuthus meridionalis]]'', the "southern mammoth" living in Southern Europe and West Asia, and ''[[http://en.wikipedia.org/wiki/Mammuthus_africanavus Mammuthus africanavus]]'', the African ancestor of the mammoths, living in Africa — the land from which mammoths originated. Giant mammoths of the ''columbi'' species have been discovered in famous U.S. tar pits like [[http://en.wikipedia.org/wiki/La_Brea_Tar_Pits La Brea]] along with mastodons, saber-toothed ''Smilodon fatalis'' and many other mammals (prehistoric camels, giant ground sloths, giant wolves, pronghorns, American lions and so on), some of them still living today and others that went extinct after the Ice Ages. Mammoths' lifestyle was probably analogue to modern Asian and african elephants, with one matriarch leading the single herd, and the huge-tusked bulls living more lonely throughout the year.

The lesser popularity of the giant mammoths (despite their size) compared to the woolly one is probably due to their more "normal" appearance. They were more similar-looking to modern elephants than to the popular image of a "mammoth" because they were mostly hairless and with straighter tusks. These tusks were nonetheless more curved than every modern elephant, and ''much'' bigger — up to 5m / 15 ft long and weighing 200kgs or more, they were the biggest/longest teeth known so far in the Animal Kingdom. These tusks tended to be straight at the basis and curly only at their tip, unlike those of the woolly mammoths. Only large ''Palaeoloxodon'' elephants and some "mastodonts" like ''Anancus arvernensis'' had tusks of comparable size of the male mammoths (''Mammuthus''). Females of the giant mammoths had smaller tusks, like what is visible in the woolly mammoth remains.

Giant mammoths inhabited relatively warmer climates, and their greater size was enough to preserve heat without a woolly coat. Think the ''mûmakil'' from ''Film/TheLordOfTheRings''; okay, not ''quite'' that big (nor six-tusked), but generally similar in appearance. It's easily thinkable that the giant mammoths of the [[http://en.wikipedia.org/wiki/Mammoth_steppe Ice Age steppes]] feared no predator as adults, like the earlier "giraffe-rhino" ''Paraceratherium'' of Oligocenic Asia.

It's worth noting that mammoths as a whole actually thrived even after the end of the Ice Age, as there was more food available. Therefore, it was almost certainly humans changing their habitat that drove them to extinction, evidenced by the fact that populations on islands lasted much longer than in the more easily-accessed mainland areas.

Among extinct members of the elephant clan, don't forget some island-dwellers which lived in the Ice Ages and managed to survive until in recorded history: the oxymoronic [[OxymoronicBeing dwarf elephants]]. Yes, they were REAL, and some were even ''sheep-sized'': true miniatures of modern elephants, like Gulliver's famous Lilliputians.

Most of them lived in the Mediterranean islands; especially famous is ''[[http://en.wikipedia.org/wiki/Palaeoloxodon_falconeri Palaeoloxodon falconeri]]'' or ''Elephas falconeri'', the Sicilian/Maltese dwarf elephant, also because of the possible link with ancient legends from European Antiquity (see below). But others lived elsewhere; there were some dwarf ''mammoths'' living on the Channel Islands off southern California (descended from the gargantuan Columbian mammoth) and on Wrangel Island off eastern Siberia (descended from the woolly mammoth): the latter managed to survive until about 4,000 years ago, contemporaneous with AncientEgypt. All achieved their dwarfism probably due to a lack of abundant vegetation and/or because they lost the necessity to defend against big mainland predators. These species were all driven to extinction by humans. As for how they ended up on islands in the first place? In most cases they swam (elephants are excellent swimmers), while the Wrangel Island mammoths walked there back when the Arctic Ocean was fully iced over.

There's a theory that elephant and other proboscidean bones found in the Mediterranean were identified by the ancient Greeks as the remains of monsters, heroes and mythical animals from the [[Myth/ClassicalMythology Age of Heroes.]] Some of these bones were identified as cyclopes, due to the alleged misunderstanding of the elephant's nasal opening, placed where cyclopes would have their one eye. But this theory itself is doubted by many historians. No elephant skulls were found, as is often claimed. The fossils of Ancient Greece and Italy are far too fragmentary due to geological forces — earthquakes and volcanoes like the Sicilian [[https://youtu.be/_Qy2RrDNCHs Etna]], the biggest volcano in Europe (where cyclopes were said to live, according to Homer's Odyssey) to allow something as fragile as a skull to survive intact.

When we think North American wildlife, we tend to think stuff like bears, bison, deer, wolves, and cougars. So it comes as a surprise to many to learn that camels (and their South American relatives, the llamas and alpacas; together, they form the family Camelidae) were once considered characteristic of North American fauna. Indeed, camels and llamas ''evolved'' in North America and were ''only'' found on that continent until relatively recently when the ancestors of today's dromedaries and Bactrians (both in the genus ''Camelus'') crossed over the Bering land bridge into Asia and the ancestors of llamas and alpacas (genus ''Lama'') entered South America across the newborn Isthmus of Panama during [[https://en.wikipedia.org/wiki/Great_American_Interchange the Great American Biotic Interchange]].

Now we enter the realm of extinct Marsupials. ''Diprotodon'' ("two teeth in front") was related to modern wombats, but was a lot bigger: the largest species reached the size of a rhinoceros, and was the biggest marsupial ever known. With its robust limbs and massive body, it literally looked like a hornless rhino or a small-mouthed hippo, and also like several extinct ungulates like the South American ''Toxodon'' or the early ''Coryphodon''.

Australian marsupials have undergone an extraordinary case of convergent evolution with placental mammals. Among differences between diprotodonts and ungulates, other than (of course) their reproductive system, is that the former had the same rodent-like incisors seen in modern wombats. We know that the diprotodon's hide was not naked or toughened like a modern rhino or hippo, but hairy like a wombat, and it had a pouch with a backward-facing opening just like the latter. Its paws were more similar to those of a bear than to a rhino or a hippo, and many illustrations portray this overgrown marsupial rather bear-like, like a koala or a wombat indeed.

''Procoptodon'' deserved the title of "giant kangaroo" more than modern giant Red or Grey kangaroos (''Macropus rufus'' and ''Macropus giganteus''). It was taller and more massively-built than both, with a shorter tail and more robust forelimbs. It's the biggest known kangaroo ever, and is also known as the short-faced kangaroo because of its flattened muzzle, which looked like a koala's. Its pouch was similar to modern female kangaroos, but its hindfeet had a single horse-like hoof each — the only digit present on each foot. Its body frame and limbs were much stockier than modern kangaroos, and this, together with the flat face, almost made it looking like a giant erect ape.

Unlike modern kangaroos, which are all grass-grazers, ''Procoptodon'' was arguably a browser of trees a bit similar to ground sloths, which used its robust forelimbs to pull down branches. [[ScienceMarchesOn Recent research]] seems even to indicate it was too heavy to hop on two legs, and walked instead rather like an erect ape or an ostrich. For this reason, it would have maintained a different stance from its modern relatives, by keeping its heels off the ground and standing on its hoofs like a horse. We don't know at all if it "boxed" with other conspecifics like modern male kangaroos do, nor of it had the same ability to bear three cubs at different stages of development of modern female kangaroos.

These two giant mammals from the LandDownUnder are more excellent examples of MixAndMatchCritter-s, and the two most commonly-portrayed herbivorous prehistoric marsupials in media because of [[BiggerIsBetter their size]]. They could have been portrayed even in prehistoric paintings made by the ancient Aborigines of the Stone Age, maybe even in Ayers Rock.

Modern Australia was also home to a unique animal which has no close modern relatives, with its contemporary the koala, wombat and the Diprotodonts above being closest despite being herbivores: ''Thylacoleo'' ("pouched lion"), nicknamed the "marsupial lion", whose most known species is named ''carnifex'', meaning [[NamesToRunAwayFromReallyFast "executioner"]]. Related to it but much smaller were the recently-discovered ''Wakaleo'' and ''Microleo''.

The marsupial lion was so-called because its body shape, sharp claws, and short head remember modern big cats, but unlike the latter, it had ''rodent-like incisors'' (like wombats and ''Diprotodon'') instead of the classic fangs, and "guillotines" instead of carnassial molars, that it used to slice the neck of prey to kill it instantly.

Scientists once thought ''Thylacoleo'' was herbivorous like a wombat or rabbit because of its incisors; [[ScienceMarchesOn they now know]] it was predatory. Not only that, it may have been the most efficient mammalian predator ever. Despite being no bigger than a jaguar, some think it was able to kill even the Diprotodonts and giant kangaroos above! The combination of ''Velociraptor''-like claws in its forelimbs and guillotines in its mouth proved an efficient killing arsenal. If not for the fact there were two larger, faster, equally well-armed reptilian predators — ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Quinkana]]'', a terrestrial crocodile, and the better-known giant monitor lizard ''Megalania prisca'' — it would have been the continent's unrivalled predator.

All three critters, modern animals adapted to today's world, met an untimely end at the hands of humans, as they set fires to grow different plant species, which starved their prey to extinction. The same fate occurred to all species of marsupial "wolves", the other main mammalian predators of prehistoric Australia other than the "lion", whose only species to have survived into the modern age, the famous "Tasmanian wolf" (''Thylacinus cynocephalus''), missed the chance to be observed by modern wildlife lovers only by a matter of decades. See the "Historically-Extinct Mammals" folder below.

Though not "marsupials" per se, and thus possibly lacking a true "pouch" just like some South American opossums, Sparassodonts were a closely-related lineage of carnivorous mammals that dominated South America before the Pliocene. The largest and most well-known of these was ''Thylacosmilus atrox'' ("atrocious pouched knife").

The same size as the marsupial lion but slenderer, ''Thylacosmilus'' had two upper fangs virtually identical to actual saber-toothed cats (and possibly used in the same way), but unlike the latter, they were ''ever-growing'' like an elephant's tusks or rodent's incisors. To protect these fangs, the lower jaw has a couple of bizarre bony sheaths covered with skin, which could have given it a curious drooping-lipped appearance. Some think even real saber-toothed cats had drooping lips to contain the "sabers" when the mouth was closed, but if they had these lips they were fleshy and not bony like those of ''Thylacosmilus''.

The most curious thing, however, is ''Thylacosmilus'' was not Australian at all: it was ''South American''. Together with the other (non-saber-toothed) sparassodonts such as the bear-like ''[[http://en.wikipedia.org/wiki/Borhyaena Borhyaena]]'' and the weasel-like ''[[http://en.wikipedia.org/wiki/Cladosictis Cladosictis]]'', ''Thylacosmilus'' long occupied the mammalian predator niche in South America. It was one of the top predators in this landmass, in competition with [[UsefulNotes/StockDinosaursSaurischianDinosaurs terror birds]] and [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles large crocodilians]]... before becoming extinct for unclear reasons. It was long thought that true placental sabertooths outcompeted it to extinction, but it appears sparassodonts were gone long before placental carnivores arrived. Furthermore, research published in 2020 seems to show that ''Thylacosmilus'' had a decidedly un-catlike hunting style. Instead of using its huge teeth to stab its victims' throats, as saber-toothed cats are believed to have done, it probably used them to [[GroinAttack slash open their abdomens]] and feed on their internal organs.

In old illustrations, both ''Thylacosmilus'' and ''Thylacoleo'' are often portrayed with a literal cat-like external appearance, with the same eyes, ears, body, fur, or even retractable claws of real felines, but since both weren't related with them at all, this could be considered artistic license. Sadly, neither the giant herbivores of Australia nor the two "marsupial cats" appear in ''Series/WalkingWithBeasts''; interestingly, the producers initially planned a seventh episode with Australian Ice Age fauna — thus giving at least ''Thylacoleo'' the chance to appear — but this program [[TheyWastedAPerfectlyGoodPlot never materialized]].

When we think North American wildlife, we tend to think stuff like bears, bison, deer, wolves, and cougars. So it comes as a surprise to many to learn that camels (and their South American relatives, the llamas and alpacas; together, they form the family Camelidae) were once considered characteristic of North American fauna. Indeed, camels and llamas ''evolved'' in North America and were ''only'' found on that continent until relatively recently when the ancestors of today's dromedaries and Bactrians (both in the genus ''Camelus'') crossed over the Bering land bridge into Asia and the ancestors of llamas and alpacas (genus ''Lama'') entered South America across the newborn the Isthmus of Panama during [[https://en.wikipedia.org/wiki/Great_American_Interchange the Great American Biotic Interchange]].

Even despite the migrations, camels remains abundant in North America all the way until the very end of the Ice Age. The most prominent of these is ''Camelops hesternus'' ("camel face of yesterday"), a fairly modern-looking camel about the same size as a Bactrian camel. Also known as the western camel or yesterday's camel, ''Camelops'' was a grazer like the Bactrian camel, and ranged from Alaska to Mexico. Its fossils are quite common in the La Brea Tar Pits, but no preserved soft tissues exist for ''Camelops''. We don't know if it had a hump, but most reconstructions choose to depict it as either humpless or having only a single very small hump. Given that its range included the Mojave and Sonoran Deserts, a hump could have come in handy. Also, nobody can prove if it "spitted" for defense against enemies like llamas and alpacas do. ''Camelops'' disappeared at the end of the Ice Age alongside the mammoths, sabertooths, and ground sloths, ending the native camel lineage in North America for good.

It's not common to see prehistoric rodents and other usually small-sized mammalian groups like rabbits, bats, "insectivores", or pangolins in popular media. However, these guys tend to be a bit more commonly-seen than the others.

''Castoroides'', the giant beaver, means "similar to a beaver" (''Castor fiber'' in Latin): indeed, it was of the same rodent family as modern beavers, the Castorids, but was ''as large as a small bear'' (three times heavier than the capybara, the largest modern rodent) and with extremely powerful incisors, possibly the most powerful ever among rodents, and arguably able to bring down even tougher trees than modern beavers.

It lived in Ice Age North America and was thus a member of the Ice Age megafauna, but it wasn't the biggest rodent ever — some [[UsefulNotes/PrehistoricLifeMammals South American rodents]] were as large as a large cattle or a small rhinoceros! Due to its size and massive build, shared also by modern beavers, ''Castoroides'' was probably rather slow-moving on land, and may have been prey for the saber-toothed cats, American lions, and dire wolves.

The main difference from modern beavers other than the size is that ''Castoroides'' was more land-dwelling, and thanks to its cylindrical (either hairy or scaly) tail it looked more similar to a large muskrat or coypu than to a beaver at a first glance. We don't know if it built woody huts or dams in rivers like modern beavers do; it is also uncertain if it dug burrows in soil like many modern rodents, but one smaller earlier castorid, ''[[UsefulNotes/PrehistoricLifeMammals Palaeocastor]]'' ("ancient beaver") did dig strange corkscrew-like burrows in North American prairies; this animal was more similar to a marmot or a woodchuck than to a beaver in size, shape, and behavior.

Another prehistoric rodent fairly common in docu-media is the so-called "horned gopher", ''Ceratogaulus''. Formerly known as ''"Epigaulus"'', was not related to marmots and ground squirrels (genus ''Marmota'', ''Spermophilus'', and others of the family Sciurids) or pocket gophers (the family Geomyids, commonly known as simply "gophers"), but belonged to an extinct family of rodents: the Mylagaulids. The prefix ''Cerato-'' ("horned") indicates its peculiarity: a unique two-forked bony projection above its nose no other rodent has ever had, recalling that of the more famous and totally unrelated brontothere ''Megacerops'', or even that of the pseudo-deer ''Synthetoceras'' or the pseudo-rhino ''Arsinoitherium''. This makes this critter the smallest known horned mammal of all time.

Apart from this, the epigaulus was not so different from other rodents of the past and the present: it resembled a [[MixAndMatchCritter horned guinea pig]] in size and shape, and lived before the giant beaver ''Castoroides'', in Miocene and Pliocene prairies of North America, digging burrows with its robust forefeet similar to true pocket gophers. It's not known if it could store seeds in cheek-pouches like them, however. Interesting that even a burrowing true armadillo of South America of the same period developed strikingly similar nasal "horns" by convergence: ''[[UsefulNotes/PrehistoricLifeMammals Peltephilus]]''.

Among the megafaunal mammals that roamed North American Pleistocenic landscapes (in a time when humans still lived only in Africa and Eurasia), besides the more famous mammoths, mastodons, sabertooths, ground sloths, and dire wolves, there were also several species of true bison (belonging to the scientific genus ''[[ExactlyWhatItSaysOnTheTin Bison]]'').

The most famous, but not the biggest, is probably the Steppe Bison, ''Bison priscus'' (perhaps the one live-acted in the last episode of ''Series/WalkingWithBeasts''), closely related to the two modern species (''Bison bison'', the familiar American bison, and ''Bison bonasus'', the rarer European bison or wisent). It was, however, a bit bigger than both, similar in size to the largest modern wild bovine, the so-called "Indian bison" or gaur (''Bos gaurus'', probably more closely related to domestic cattle). The Steppe bison had, more strikingly, longer horns than its two living kin — more like those of an African Cape buffalo or Indian water buffalo. It also lived in contemporaneous Eurasia, from which it actually originated.

An especially famous specimen of ''Bison priscus'' was found mummified in Alaska in 1979; nicknamed "Blue Babe" because of the color it has assumed, its frozen meat was still edible (its discoverers actually ate a chunk of it!) and its corpse shows perhaps signs of attack from Ice Age American lions (''Panthera atrox''). The carcass is wonderfully preserved, even more than many woolly mammoth specimens, resembling almost a living bison, and the animal appears lying on its knees like a "sitting" bison.

The Long-Horned Bison, ''Bison latifrons'', is today the biggest known wild bovid, and its name means "wide-front bison". Unlike the Steppe Bison it lived only in Pleistocene North America, but its horn-span reached 7 ft/2 m of wideness, more than a standing human, but still less than the horn-span of ''Megaloceros giganteus'' (the Irish Elk). It was arguably a more difficult meal for predators than ''Bison priscus''.

!! Lofty Critters: ''[[http://en.wikipedia.org/wiki/Aepycamelus Aepycamelus]]'' and ''[[http:/en.wikipedia.org/wiki/Camelops Camelops]]'' *

The giant "giraffe-camel" ''Aepycamelus'' is the most famous extinct camelid, and lived earlier than ''Bison priscus'', in Miocene North America. Other big, more modern-looking camelids like ''Camelops'' ("camel face") roamed North America later, in the Ice Ages. The latter was also found in the famed pleistocenic tarpits whose most iconic animal is ''Smilodon'' (a possible predator of it). The biggest known camel is the recently-extinct [[http://en.wikipedia.org/wiki/Syrian_camel Syrian Camel]], very close to modern camels and dromedaries.

In older media ''Aepycamelus'' is often called "Alticamelus": both names mean "lofty camel", but ''Aepy'' is Greek, ''Alti'' is Latin. It was indeed taller than the already-tall modern dromedaries (up to 3m), but not much heavier: it was slender and had especially long limbs and neck, convergent with modern giraffes.

Unlike the most primitive camelids, ''Aepycamelus'' had already the typical flattened toes with small hooves of modern camels and llamas, but isn't known to have had a fatty hump on its back. Living in grasslands, it should not have had the desert adaptations of modern camels like the ability to store fat to survive the lack of food, or to resist thirst. Also, nobody can prove if it "spitted" for defense against enemies like llamas and alpacas do.

In media, ''Smilodon''s will also probably use their sabers for every conceivable task, most prominently slaying herbivores the size of mastodons or ''Megatherium'' with a single stab. However, most real sabertooths (as well as their relatives, the [[UsefulNotes/PrehistoricLifeMammals scimitar-tooths and dirk-tooths]]) had relatively delicate fangs that could not safely be used for stabbing. Instead, they probably used them to deliver a killing blow to the throats of their prey after disabling them. They would have preferred smaller prey too, such as juvenile mastodons and the smaller forms of ground sloth, as well as horses, deer, tapirs, bison, camels, giant armadillos, and peccaries. They may be depicted as striped or spotted, just like a ''literal'' tiger or other big cats, which isn't completely impossible, but there isn't concrete proof of this: soft tissue of skin has not been preserved in the La Brea Tar Pits, where ''S. fatalis'' has been found in large numbers (over ''2000'' individuals).

This extinct primate is surely the most popular today in media (human ancestors excluded, of course) also because of [[BiggerIsBetter its size]]. Other giant primates of the past include baboons like ''[[UsefulNotes/PrehistoricLifeMammals Dinopithecus]]'', and [[UsefulNotes/PrehistoricLifeMammals giant lemurs]] of ancient Madagascar.

According to [[ScienceMarchesOn the most recent research]], ''Gigantopithecus blacki'' was a relative of the orangutan, but also convergently exhibited gorilla-like characteristics. Found in Southern Asia from China to India, its name means "giant ape", and with good reason. It's estimated to have measured up to 10 feet / 3 meters when standing upright, ''twice'' as tall as a modern silverback gorilla; sort of midway between a RealLife gorilla and Film/KingKong. If it lived alongside dinosaurs, it could have made realistic PrimateVersusReptile.

Sadly, the only parts that can be described for certain are the jaws and teeth, while the rest of the body has yet to be recovered; the shape of the teeth show us it was a plant-eater, possibly specialized to a bamboo-based diet just like a gorilla, to the point that some experts think competition with [[KillerRabbit the giant panda]] actually drove it to extinction. ''Gigantopithecus'' lived alongside the Asiatic ''[[UsefulNotes/PrehistoricLifeMammals Homo erectus]]'' before going extinct, but we don't known how they interacted with each other due to the scarcity of remains of either.

Despite this, the "''Gigantopithecus'' = Bigfoot" theory is so popular that the ape is often depicted in models and illustrations in an upright stance like a man, just to fit with this idea. Since all we have are its jaw and teeth, it's hard to be sure, but judging by its relationship with other apes, it most likely walked on its knuckles like most great apes do today. Since primates that habitually stand and walk upright require a specialized foot structure ''extremely'' different from that of other apes, ''Gigantopithecus'' evolving a similar foot structure to that of humans would be a radical case of convergent evolution. Also, if it was as large as believed, its immense weight would cause great stress on its ankles and would be better-distributed by walking on all fours.

In TheNewTens, ''Gigantopithecus'' made two notable film appearances. First, there was the villainous pirate Captain Gutt in ''WesternAnimation/IceAgeContinentalDrift''. Then in ''[[Film/TheJungleBook2016 The Jungle Book]]'', a 2016 remake of [[WesternAnimation/{{The Jungle Book|1967}} the 1967 Disney classic]], King Louie was [[AdaptationSpeciesChange changed]] from an orangutan to a surviving ''Gigantopithecus'', averting MisplacedWildlife in favour of AnachronismStew (orangutans live in South Asia but they survive only in Indonesia and Malaysia, not in India where the story is set; although ''Gigantopithecus'' don't live anywhere at all, and have been extinct about 350,000 years... probably). The latter appearance could very well place this creature in the public's mind for quite a long time, since not only was he quite humorous, being voiced by Creator/ChristopherWalken and all, but he was much more menacing than his 1967 counterpart, chasing Mowgli through the ancient temple ruins in a memorably chilling sequence. That said, both film appearances [[ShownTheirWork correctly]] depict ''Gigantopithecus'' as an orangutan-like ape, walking quadrupedally on its knuckles as opposed to upright like a human.

''Macrauchenia'' was another famously [[MixAndMatchCritter enigmatic]] prehistoric creature that lived in the Ice Age (but also earlier); its best-known species is ''Macrauchenia patachonica'', meaning "Patagonian long/big llama". It did indeed resemble a llama or humpless camel in appearance, but actually belonged to a long-extinct group of mammals called the Litopterns, with no modern relatives — though [[ScienceMarchesOn recent research shows]] this group to be a sister group to Perissodactyls, the odd-toed ungulates.

The size of a horse, one of its most distinct features is its nostrils, which on the skull were located on its ''forehead'' like in tapirs and in the proboscideans (elephants, mammoths, and so on) . This results in it always being depicted with a flexible tapir-like proboscis. However, if you compare a [[http://www.boneroom.com/uploads/4/8/1/1/48118243/s521972503441136676_p1269_i1_w338.jpeg tapir skull]] to that of ''[[http://www.gastondesign.com/wp-content/uploads/macrauchenia-skull_fs.jpg Macrauchenia]]'', you can see that the tapir has a bony projection on its forehead to hold the proboscis in place, which ''Macrauchenia'' lacks. Therefore, it's more likely the animal had a bulbous trunk similar to that of a [[http://en.wikipedia.org/wiki/Saiga_tatarica Saiga antelope]].

Another distinctive feature of the ''Macrauchenia'' is its leg bones, which were not only built for extremely high speeds, but also some of the sharpest turns of any herbivorous mammal. This makes sense when you realize it evolved alongside the famous [[UsefulNotes/StockDinosaursSaurischianDinosaurs terror birds]], which were not only fast runners but, like most birds, had very good color vision, meaning camouflage was useless. Other predators of ''Macrauchenia'' included a group of carnivorous marsupial-relatives common in South America named Sparassodonts, like ''Borhyena'' and the saber-toothed ''Thylacosmilus'', and, after the Great American Interchange, North American "invaders" like cougars, jaguars, the giant bear ''Arctotherium'', and, most famously, ''Smilodon''. When dead, it could have been eaten by the gigantic flying "vulture" ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Argentavis]]'', which lived in Pliocenic Argentina together with it.

''Macrauchenia'' lasted a good seven million years from the Late Miocene to the Late Pleistocene, until it went extinct after humans entered South America. Pop culture appearances include ''Series/WalkingWithBeasts'', the ''WesternAnimation/IceAge'' franchise, and even an episode of ''{{WesternAnimation/Futurama}}''. However, when it appears in non-documentary fiction, don't expect it to be referred to by name — like the vast majority of prehistoric mammals. Expect also to see it with the tapir-trunk, due to ScienceMarchesOn.

Though slightly less often-portrayed than ''Macrauchenia'', ''Toxodon'' also make occasional appearances in media, e.g. in the ''Series/PrehistoricPark'' series — in which is shown as the main herbivore of the time and as a ''Smilodon'''s prey, substituting in this role for ''Macrauchenia'' of ''Walking with Beasts''.

''Toxodon'' ("bow tooth") was bigger than the "tapir-camel", being one metric ton or so in weight, and was probably the most common plant-eating mammal in the South American Pleistocene (the Ice Age), but lived also earlier, since the Miocene. Like ''Macrauchenia'', it wasn't closely related to any modern group of ungulates. ''Toxodon'' belonged to the Notoungulates, lit. "the southern ungulates", and was one of the biggest and latest-surviving members of the group. When discovered in the 1800 century its skull was only known initially, and it was believed a sort of manatee. Together, ''Macrauchenia'', ''Toxodon'' plus other South American mammals make together the "Meridiungulates", also meaning the "southern ungulates".

Its look may recall for some that of a stockily-built, hornless buffalo, but it had a wider mouth-opening and strong incisors like a horse. Its body and limbs were stockier than cattle, and the feet had four or five digits with small "hooflets"; thus, it has been classically compared with a hornless rhino or a small-headed hippo. Like the pre-ice Age ''Uintatherium'' and ''Arsinoitherium'', ''Toxodon'' was once thought to have been a slow-moving animal — today we believe it was capable of running rather quickly, as popularized by ''Prehistoric Park'', where one is shown even keeping pace with Nigel Marven's vehicle. The toxodont was arguably not as fast as ''Macrauchenia'', but thanks to its massive frame and rhino-bulk it was a harder target to fight and defeat for predators than the slenderer tapir-camel. Terror-birds probably were unable to kill a fully grown toxodont, while other predators, like the mighty ''Smilodon populator'', could have been able to do so, but not easily.

These two South American guys lasted a sufficient length of time that they could have met humans in the past, like their neighbors, the giant ground sloths and glyptodonts. The last ''Toxodon''s probably went extinct a few thousand years ago, maybe depriving the ''Smilodon''s of South America of what might have been one of their main prey sources.

Before the discovery of ''Lagosuchus'' in the 1970s, other "thecodonts" were considered the direct ancestors of dinosaurs, especially the European ''[[https://en.wikipedia.org/wiki/Saltoposuchus Saltoposuchus]]'' and to a lesser degree ''[[https://en.wikipedia.org/wiki/Scleromochlus Scleromochlus]]''[[note]]The latter could be an ancestor of pterosaurs, though.[[/note]] -- and some were often even considered early proper dinosaurs (more precisely, early theropods), notably the 12ft long ''[[https://en.wikipedia.org/wiki/Ornithosuchus Ornithosuchus]]'', the 2ft long ''[[https://en.wikipedia.org/wiki/Saltopus Saltopus]]'', and the 20ft long ''[[https://en.wikipedia.org/wiki/Teratosaurus Teratosaurus]]' '. It is now understood however that ''Ornithosuchus'', ''Teratosaurus'' and ''Saltoposuchus'' were Pseudosuchians; ''Teratosaurus'' was in fact a rauisuchian like ''Postosuchus'' above -- ''Saltopus'' meanwhile was an Ornithodiran just like ''Lagosuchus'', a dino-ancestor but still not a true dinosaur.

The much smaller (2ft long) ''Mesosaurus'' has a deceptive name: it was not related at all with the much more famous ''Mosasaurus'' -- the former name means "middle-lizard", the latter "lizard from the Meuse River" (in the Netherlands). Despite this, ''Mesosaurus'' did somewhat resemble in shape the old classic illustrations of mosasaurs, being elongated, with long toothed jaws, and a powerful sideward-undulating tail for swimming. But its legs were apt for walking, like modern crocs and unlike the paddle limbs of its almost-namesakes mosasaurians (the mesosaur's limbs were palmated-footed at the most). This makes ''Mesosaurus'' actually more similar to ''Nothosaurus'' or ''Champsosaurus'' than to a mosasaurid. Like ''Champsosaurus'', it's sometimes mislabeled in paleo-media as a crocodile-ancestor, or worse, a true crocodilian. In reality, ''Meosaurus'' lived in the Early Permian, disappearing long before the the ancestors of crocodiles evolved. Adapted for freshwater or estuarine/coastal life, ''Mesosaurus'' was one of the first vertebrates to re-evolve an aquatic lifestyle and return to the water. ''Mesosaurus''' numerous tiny, needle-like teeth were adept at catching small fish, but it was too small and ill-adapted for life in the open ocean. But because its fossils are known from both Africa and South America, it was one of the main fossils used as evidence for the existence of Pangea (alongside the mammal-ancestors ''Cynognathus'' and ''Lystrosaurus'' and the plant ''Glossopteris'').

One of the first animals to have recuperated after the Permian-Triassic extinction event, ''Lystrosaurus'' was one of the most successful animals of all time; '''95%'' of all land vertebrates alive at the start of the Triassic were ''Lystrosaurus''. Its remains have been discovered everywhere in southern continents, even Antarctica (don't forget that this continent began to freeze only a few million years ago). Thanks to this, ''Lystrosaurus'' is one of the classic fossils used to prove the Pangaea supercontinent hypothesis, like ''Mesosaurus'', ''Cynognathus'', and the plant ''Glossopteris''. The size of a medium pig and thus bit bigger than ''Cynognathus'', ''Lystrosaurus'' has the typical dicynodontian shape: bulky, stubby-tailed, with strong semi-erect limbs, and the typical dentition made up of only the two upper tusk-like "canines". Formerly, [[ScienceMarchesOn it was depicted as a freshwater dweller like a hippo]], but now is mostly believed to have been a grazing land animal. In paleo-art, it is often shown as the favourite prey of ''Cynognathus'', but in reality, ''Cynognathus'' lived slightly later than ''Lystrosaurus'' -- ''Cynognathus'' instead lived alongside the aforementioned ''Kanneyemeria'', while ''Lystrosaurus'' coexisted with ''Thrinaxodon''.

The "sabers" of ''Smilodon'' were arguably used only for slashing the throats of prey that had already been subdued with its bodybuilder-like forearms; the molars and lower canines were smaller than those of modern cats but the incisors were bigger, and more apt than the canines for tearing off flesh from its prey's body. ''Smilodon'' is often portrayed living in wolf- or lion-like groups with both sexes actively hunting, though this is considered controversial by some scientists as there is not enough actual evidence to support it. Some artists have even depicted smilodonts with a totally speculative [[PantheraAwesome lion mane]], linking it with the social behavior that is practiced by lions but unusual for other modern felines. The modern feline with the longest fangs today in respect to the body is the smallish clouded leopard of Asia; the one with the bulkiest body-frame is the larger jaguar (''Panthera onca'') of the Americas. The overall biggest modern feline is ''Panthera tigris altaica'', the Siberian Tiger, with some individuals getting as big as extinct cave lions or American lions.

''Megatherium'' is the most well-known species of ground sloth, due to [[BiggerIsBetter being the largest]], hence its popular name, the giant ground sloth. The only similarly sized ground sloth alive at the same time was the Central American ''Eremotherium laurillardi'', the Panamerican ground sloth. Like ''Smilodon'', it's commonly depicted [[MisplacedWildlife alongside the aforementioned mammoths]], despite being strictly South American (mammoths never reached this continent). The proboscideans that ''did'' reach South America, such as ''Cuvieronius'' and ''Notiomastodon'', are classified as gomphotheres, a primitive family more closely related to elephants and mammoths than mastodons were. Different sloth species that reached North America, such as ''Nothrotheriops'' and ''Megalonyx'', would've been the ones contemporary with mammoths and the American mastodon.

''Megalonyx jeffersoni'', or Jefferson's ground sloth, was the ground sloth species most common in North America, but it was about half the size of its more famous cousin. It was first described in 1797, believe it or not, by UsefulNotes/ThomasJefferson! Naming it based only on some claw bones, he tentatively classified it as being a huge lion (it was properly identified as a sloth in 1799, though the not-yet President did acknowledge similarities to the then-new ''Megatherium'' in his original description). Since the existence of prehistoric life was still controversial at the time, he believed ''Megalonyx'', as well as mammoths and mastodons, could have still been existing in the American wilds -- he even asked Lewis and Clark to find him live specimens on their expedition! Two other similarly-sized North American grounds sloths are ''Paramylodon harlani'' (Harlan's ground sloth) and ''Nothrotheriops shastensis'' (the Shasta ground sloth); contrasting with the forest-dwelling ''Megalonyx'', the former was a grasslands animal commonly found in the La Brea Tar Pits, while the latter preferred deserts. Among the "small" ground sloths of South America, the most notable is ''Mylodon darwini'', the first fossils of which were ''Mylodon'' were found by Charles Darwin during his voyage on ''HMS Beagle'', earning it the common name of Darwin's ground sloth. The Caribbean also supported many dwarf ground sloths that survived until 5000 years ago when humans colonized the islands, long after their huge mainland kin went extinct.

''Elasmotherium sibiricum'' ("Siberian thin-plate beast"), also known as the Siberian unicorn, is probably the biggest true rhinoceros known: it's often confused with the proper woolly rhino (''Coelodonta antiquitatis'', "hollow tooth of antiquity") because of their similar appearance. However, the woolly rhino was no larger than modern white rhinos and had ''two'' horns as well; it was closely related to the modern Sumatran Rhinoceros, the smallest extant rhino species (and the only one with some hair on its body). ''Elasmotherium'', on the other hand, was much larger (5 tons, like a modern bush elephant) and with a single horn... on its ''forehead'' rather than its nose; hence [[ExactlyWhatItSaysOnTheTin the "unicorn" label]]. Unlike the "woolly", the Siberian unicorn was not closely related to any of the five modern rhinoceros species, though it still belonged to the rhino family, Rhinocerotidae.

Both rhinos lived in the Ice Age in cold climates alongside the other, more popular woolly ([[MammothsMeanIceAge guess what]]). But whereas the elasmothere was restricted to Eastern Europe and Central Asia, ''Coelodonta'' ranged as far as Spain (there is, however, a cave painting that might stretch ''Elasmotherium'''s range as far as France). Like the elephantine "woolly", the rhinocerotine one (we're always talking about ''Coelodonta'') has left behind soft parts of its body, hair and horns included, in the form of frozen corpses.

Unlike the woolly rhino, we don't know what size and shape the elasmothere's horn actually was, because it has never found. Traditionally, it's been believed that it was enormous, as long as a man is tall and possibly the longest horn in the animal kingdom. More recently though, it's been suggested that the elasmothere's horn was actually short and blunt, something along the lines of the modern-day Javan rhinoceros -- in which case ''Elasmotherium'' might not quite have been the "prehistoric unicorn" it is often imagined to be. Both the woolly rhino and Siberian unicorn had three toes for each foot like the modern ones, and probably reproduced in the same manner, giving birth to one (hornless) calf after a very long gestation, like modern rhinoceroses but unlike hippopotamuses, whose pregnancy is rather short for their size (8 months vs. a rhino's 18). Both rhinoceroses went extinct without leaving descendants. Like with many of the Ice Age megafauna, it appears the combined pressures of human hunting and climate change did these creatures in.

Among the prehistoric mammals of the order Carnivora, the most famous after the saber-toothed cats are the giant bears, again from the Ice Ages.

The most well-known is the cave bear (''Ursus spelaeus'', meaning [[ExactlyWhatItSaysOnTheTin "cave bear"]] in Latin), so-called because its remains are extremely abundant in European caves, more than those of other "cave-mammals" (see further). The cave bear is probably at the origin of the subtrope to putting "cave" before the name of fictional extinct animals, falling in WhateverSaurus.

Quite similar to a modern Kodiak bear in shape and size, but with a bigger hump on its shoulder and a more prominent skull, the cave bear was perhaps the closest relative of brown/grizzly/Kodiak bears (''Ursus arctos''), and usually depicted with the same brownish color of the latter, as cave paintings suggest. It was also related with the polar bear, an animal that recently evolved from the brown bears modifying its anatomy to live in the icy seas of the North Pole, together with a [[PolarBearsAndPenguins penguin-like]] bird recently extinct in 1800, the [[UsefulNotes/StockDinosaursSaurischianDinosaurs Great Auk]]. As recently as in 2020, the first frozen mummy of a cave bear specimen has been found in Siberia.

The cave bear was probably a mainly peaceful creature that cared its tiny offspring in its warm rocky homes; but it had also classically been described as [[BearsAreBadNews the archenemy of Neanderthals and Cro-Magnon humans]], because both humans and bears lived in the same places (Pleistocene Europe) and were forced to share the same caves to protect themselves from the frigid Ice Age winters. But it's more probable that Neanderthals and Cro-Magnons were actually the worst enemies of cave bears, and some think they could even have contributed to the bears' extinction. Studies show the cave bear to have been to an almost pure herbivore, like the living giant panda, living on a strict diet of berries and shrubs (though, like pandas, it may have supplemented its diet with meat every now and then). In fact, the inflexibility of its diet may also have contributed to its extinction.

The North American short-faced bear (''Arctodus simus'', lit. "short-muzzled toothed bear"), in contrast to its stockier cousin, had long limbs, a [[ExactlyWhatItSaysOnTheTin bulldog-like snout]], and (it's usually thought) an almost purely carnivorous diet. At first glance, it seems like it would be an agile and fast runner, and a very powerful hunter. However, [[ScienceMarchesOn more recent studies]] show that its limbs were too gracile to wrestle large prey to the ground, and too fragile for sharp turns, the latter of which are required for a fast-running hunter. More likely, it was a scavenging "kleptoparasite" that stole prey from other predators by scaring them away with its large size. On the other hand, very few animals can live entirely on scavenging (vultures are an exception, as they can fly for miles without eating), hinting that it may have been an omnivore like other bear species. Bears in general can be qualified as LightningBruiser, like rhinos/hippos, as they are massive but fast runners compared with the probably slower giant sloths and glyptodonts.

Expect these two bears to be confused in pop culture despite being quite different in appearance, and the short-faced bear being more related to the South American [[http://en.wikipedia.org/wiki/Tremarctos_ornatus Spectacled Bear]] (''Tremarctos ornatus'') than the modern grizzly, while the cave bear was a close relative of every other ''[[http://en.wikipedia.org/wiki/Ursus_(genus) Ursus]]'' species. Also expect the cave bear to be depicted as a hunter of large prey despite having a mostly herbivorous diet judging from the wear on its teeth. Another thing to note is that despite most books describing the short-faced bear as the largest bear, that title actually belongs to its South American relative ''[[http://en.wikipedia.org/wiki/Arctotherium Arctotherium]]'' ("bear beast").

After [[UsefulNotes/StockDinosaursOrnithischianDinosaurs ankylosaurs]] went extinct, evolution decided to create their perfect mammalian equivalents: the glyptodonts. They were basal placentals of the same group as the giant ground sloths (the Xenarthrans or Edentates), but evidently more related to armadillos rather than to sloths. Despite the old name "edentate" means "no teeth" (a reference to anteaters, which are xenarthrans as well), both ground sloths and glyptodonts had strong molar-like teeth to grind up vegetation, but small or no frontal teeth.

Glyptodonts lived in South America for a dozen million years, before going extinct only a few thousand years ago: in other words, they had the same history as their cousins, the giant sloths. Both groups were herbivores, and glyptodonts fortunately have never been depicted as meat-eaters or predators in popular media unlike their relatives. Rather, they have often been compared with giant tortoises because of their shell-like armor and short "hoofed" feet. Like the megatheres, as adults they feared no predators (not even the saber-toothed cats), except of course humans. The size of the largest glyptodonts tends to be sometimes exaggerated in docu-media; they were actually much smaller than ''Megatherium'', being not taller than an adult man — but their mass was nonetheless as much as a small car, and thanks to their heavy armors they weighed two tons, like a modern rhino or hippo (which is still smaller than the elephant-sized ''Ankylosaurus'').

There is a secret behind giant sloths' and glyptodonts' success: their backbone. It was far, far stronger than that of any other mammal, thanks to special protrusions (the xenarthral bones, hence the name "Xenarthrans" given to their group) in their vertebrae that permitted them to carry such heavy bodies around without suffering back pain. Some think glyptodonts were even able to briefly rear up on their pillar-like hindlegs, which had enormous femurs and insanely robust pelvis (like those seen in the ground sloths), making them analogue to stegosaurs. But unlike stegosaurs, glyptodontids were live-bearers, and like modern armadillos their young were born from their mothers already with their armors formed.

''Glyptodon'' ("sculpted tooth") is the prototypical and most well-known glyptodont, with many species described, among them the type species ''G. clavipes'' (the latter word meaning "club-foot"); it had a round upper shell like a tortoise, coupled with a small round head (perhaps ending with a small "trunk" as show in some illustrations), and short stocky tail all covered by small but pointy spikes. The modern animal that perhaps resembles ''Glyptodon'' the most is the 30 kg giant armadillo, ''[[http://en.wikipedia.org/wiki/Giant_armadillo Priodontes maximus]]'', of the Amazon Basin.

But it's also worth mentioning the even more armored ''Doedicurus clavicaudatus'' (lit. "club-tailed pestle tail": this is the biggest/longest known glyptodont, and the one seen in ''Walking With Beasts'', ''Zoo Tycoon 2'', and ''ARK Survival Evolved''). It was very similar to ''Glyptodon'', but with its long flexible tail covered in massive spikes at the end, it was the most stegosaur- or ankylosaur-like of all glyptodonts, easily able to kill even a smilodont with a single blow from its "[[BewareMyStingerTail Medieval mace]]". The doedicurus' spiky tail-end would have been even more dangerous for enemies than the Ankylosaurus' more rounded one — recalling more a stocky ''Stegosaurus'' "thagomizer". These two glyptodonts are [[BiggerIsBetter the most-often depicted]] of the group, also because they were among the biggest and most powerfully-armed.

Glyptodonts' dorsal armor was the strongest among any land vertebrate, tortoises excluded. It was made of a ''single piece'' consisting of several scutes fused together, smooth and usually round, unlike ankylosaurs and armadillos whose armor was more flexible (and spiky in the case of ankylosaurs). With their compact frame, pillar-like legs, and rigid armor, glyptodonts were probably slower-moving than ankylosaurs and armadillos, but still faster than a Galapagos tortoise. Despite these differences, the glyptodont's armor was astonishingly similar to an ankylosaur's; only the upper parts of the body were covered, the underbelly was unarmored like ankylosaurs and hairy like modern armadillos; the head had a "shield" again like ankylosaurs and armadillos, and their tail was also covered by bone all around it.

We don't know if megatheres and glyptodonts were solitary or lived in herds: modern xenarthrans are usually solitary, but the nine-banded armadillo has the singularity to give birth to four twins all the same gender.

Like ''Megatherium'', ''Glyptodon'' was known to ancient humans; if seen from far distances, it could have given to us the curious impression of a big walking ball roaming slowly across the grasslands. Despite appearances, "glyptos" were totally unable to roll in an actual impenetrable ball like what some South American armadillos, or also the unrelated pangolins and hedgehogs of the Old World, do. They weren't also able to retreat their heads, limbs and tails in a tortoise-manner, and their size, armor, and body robustness were alone effective defenses, like in marine turtles.

We now know human hunting wiped out the ground sloths and the glyptodonts, as the species on islands were the last to go, and as there is evidence of human hunting and change in their habitat. Ancient humans often used the biggest glyptodonts' dorsal armors as body armor for themselves. Now, only far smaller xenarthrans survive; armadillos (which were not glyptodont descendants but only relatives), tree sloths (not ''Megatherium'' descendants), and true anteater (sadly, the natural history of anteaters is poorly-understood), all Central/South American, except for the nine-banded armadillo, which has in the past few centuries colonized part of the USA.

!! Up To Eleven Trophy: ''[[http://en.wikipedia.org/wiki/Megaloceros Megaloceros]]'' **

Now we return in the world of the [[http://en.wikipedia.org/wiki/Ungulate hoofed mammals]] (remember that rhinos are true ungulates, but mammoths & elephants are not), this time with an artiodactyl, aka an even-toed hoofed mammal.

The most spectacular extinct deer, this is also one of the most-depicted extinct mammals in prehistory books because of its antlers, but is rather uncommon in Fictionland. ''Megaloceros'' simply means "big horn": continuing the RunningGag of comparing Ice Age mammals with dinosaurs, ''Megaloceros'' could be considered the "hadrosaur" of its time, for its huge size but slender running frame, spectacular head ornamentation like that of the ''Parasaurolophus'', and its ecological niche as prey for other mammals (humans included), just like "duckbills" in the Cretaceous.

But wait: even though it is commonly referred to as the Irish elk[[note]]In British English, elk = moose.[[/note]], ''Megaloceros'' (also called "Megaceros" [[ScienceMarchesOn in older sources]], with the same meaning of "big horn") was more closely related to the European fallow deer — indeed, in many sources it is more generically named the "giant deer". It wasn't the largest deer ever — though it was as large as a moose, even bigger deer lived elsewhere in the Ice Age — but its antlers were another matter: they would make a modern moose's antlers look puny. Each one was ''as long as the entire animal's body'' (each as tall as an adult person, as mentioned in ''Walking With Beasts''), and each weighed more than 100kg — more than any other known deer species. They are probably the biggest known "horns" (sensu lato) of every mammal, and rivalled even the biggest horns and spikes of the ceratopsid dinosaurs; but it's possible that the unknown one horn of the giant rhino ''Elasmotherium'' was the same size, or even bigger, of the megaloceros' antlers.

As with all modern deer (except for reindeer and caribou), only males had such headgear, which in reality more resemble a moose's flat antlers than the typical deer's branched ones. Some scientists believe that ''the antlers alone'' were the cause of its extinction, having grown too big. This phenomenon is called "hyperthely": classically-cited examples of modern hyperthelies are the peacock's tail, the toucan's bill, the right pincer of the fiddler crab, and the narwhal's spiral tooth. This hypertely should have made the giant deer too clumsy... but this is uncertain. ''Megaloceros'' males were stronger than females but probably just as agile, as with extant deer species: if their antlers actually were too big, evolution probably would have just made them smaller at some point.

The species ''Megaloceros giganteus'' ("gigantic big-horn") lived in Europe in the Ice Ages alongside woolly mammoths and other large mammals, and was possibly prey for ancient humans (''Series/WalkingWithBeasts'' show Cro-Magnons successfully killing one adult male ''Megaloceros'' that was tired after a combat with another male); its nickname "Irish elk" is due to its remains being very common in Ireland. Its huge antlers are often found isolated in this country (all true deer loose and regrow their antlers seasonally), and have even been used as a tool to cross small streams! Other ''Megaloceros'' species were more common in continental Europe, but were less impressive than the Irish one and had differently-shaped antlers.

In ''Literature/TheLostWorld1912'', the explorers briefly glimpse some kind of giant deer, and protagonist Edward Malone - an Irishman - suggests that it was probably one of "those monstrous Irish elk which are still dug up from time to time in the bogs of my native land."

''[[http://en.wikipedia.org/wiki/Eucladoceros Eucladoceros]]'' ("well-ramified horn") and ''[[http://en.wikipedia.org/wiki/Cervalces Cervalces]]'' ("moose-deer"), the former nicknamed the Bush-antlered Deer, the latter nicknamed the Stag-Moose, were other large, spectacularly large-antlered, extinct ''true'' deer: the biggest ''Cervalces'' species had a smaller set of antlers, but had a larger body than the megaloceros; ''Eucladoceros'' was smaller-bodied but had an incredibly high number of points in its antlers. Other prehistoric cervids (the "deer family" of artiodactyls) had more normal-sized headgear.

Other prehistoric mammals with big antler-like things above their heads, like ''Sivatherium'' and ''Synthetoceras'', were artiodactyls but ''not'' of the deer family: the former a ''giraffe'', the latter a relative of the chevrotain or mouse deer, family Tragulids; they may nonetheless be wrongly presented as "deer" in docu-media. Of course, none of these real or pseudo-deer were direct ancestors of modern deer species.

# '''TropeMaker:''' Crystal Palace Park in London (believed the most realistic animal model of the park)

The dire wolf (''Aenocyon dirus'', traditionally ''Canis dirus'') was a recently-extinct wolf exclusive to the Americas, famous for being bigger/stronger than our wolves, and possibly a hunter of giant bison like ''Bison priscus'' in competition with saber-toothed smilodonts and extinct American lions (''Panthera atrox''). It has been often found in the same tar pits in which ''Smilodon'' remains have been discovered, along with several other American mammals (elephant relatives, ground sloths, and modern mammals as well); the most famous is [[http://en.wikipedia.org/wiki/Rancho_La_Brea Rancho la Brea]], in Los Angeles. This animal could be considered the mammalian "raptor" of the Ice Ages. We don't know exactly what was its hunting style however, nor what precise color its fur was. It's unknown if its packs were dominated by an "alpha" pair like in modern wolves, but arguably it gave birth to several puppies that were raised with love, like what real life grey wolves and domestic dogs do.

Despite its fame of power and direness, the "dire wolf" wasn't much larger than the modern grey wolf (''Canis lupus''). However, it had a much more powerful bite, well over twice that of the grey wolf, and thus often compared to that of a hyena. This would allow it to be a fair competition to other predators at the time. It ranged from as far north as Canada to as far south as South America (though only in the northern and western areas, due to the obstacle presented by the Andes). Like the bears above, neither of which left descendants in modern world, the dire wolf is not the ancestor of modern wolves, nor was it closely related. In fact, the dire wolf was probably more closely related to the African jackals (''Lupulella'') and likely diverged from modern wolves over 5 million years ago. This in turn probably means it didn't really look much like a regular wolf and would have had a much more distinct appearance.

Surprisingly, this canid is less common in works set in prehistoric times, and more common in fantasy works such as ''TabletopGame/DungeonsAndDragons'' and, most famously, in ''Literature/ASongOfIceAndFire'' and its television adaptation ''Series/GameOfThrones''. When it appears, expect it to be double the size of a real grey wolf, despite not being much larger in real life. Expect it also to be described in books as "the biggest canid ever", though some [[UsefulNotes/PrehistoricLifeMammals Borophagines]], nicknamed "hyena-dogs", that lived well before it were actually larger (the record belongs to ''Epicyon''), as well as some extinct true hyenas like ''Pachycrocuta'', which are not canids at all but distant feline relatives.

#'''TropeMaker:''' ''TabletopGame/DungeonsAndDragons'' (1st Edition Monster Manual)

It's worth noting that mammoths, scientifically speaking, were just another genus of elephant, since they belonged to the same family, the Elephantidae. The Asian elephant (''Elephas maximus'') is slightly more closely related to mammoths (''Mammuthus'') than to its more distant modern African relatives (''Loxodonta africana'' and ''Loxodonta cyclotis'') -- thus mammoths (and mastodons) ''weren't'' the direct ancestors of elephants as is sometimes claimed. Also within Elephantidae was ''Palaeoloxodon'', the "straight-tusked elephant"; the best-known species of which is ''[[http://en.wikipedia.org/wiki/Palaeoloxodon_antiquus Palaeoloxodon antiquus]]''. Formerly believed to be related to Asian elephants, its now considered to be closer to African elephants. It also lived during the Ice Age, but it preferred warmer climates and was bigger than the woolly mammoth at about the same size as the Columbian mammoth. Other recently-extinct elephantids underwent a high degree of insular dwarfism, some becoming as small as an average sheep or pig.

Saber-toothed cats, with their distinctive fangs, are just as iconic in pop culture as the woolly mammoths, and the only other mammals worthy of three stars here. Mammoths and sabertooths (sabretooths in UK) have traditionally competed for the title of most iconic Ice Age mammal — just like ''Brontosaurus'' and ''Tyrannosaurus'' for title of most iconic dinosaur.

There were many species of saber- or sabre-toothed felines, but the ones you'll likely see are the North American ''Smilodon fatalis'' ("fatal knife-tooth") and the South American ''Smilodon populator'' ("devastator knife-tooth"), which was larger but whose name [[RuleOfCool sounds less cool when said out loud]] (even if its specific ''definition'' is awesome). The Old-World genus ''Machairodus'' ("sword-tooth"), often spelled "''Macherodus''" in old sources, has also been quite common, at least in non-fictional works. Estimated at around a thousand pounds in maximum weight, ''S. populator'' was one of the largest cats to have ever lived, the same size as the extinct American lion and Eurasian cave lion, and was probably a descendent of ''S. fatalis'', which was closer in size and weight to a bulky modern lion. Similar in size to the ''populator'' among true saber-toothed felines was only the little-known ''[[http://en.wikipedia.org/wiki/Amphimachairodus Amphimachairodus]]''.

Although sabertooths belongs to the cat family Felidae, they are in a separate branch of that clade from modern felines, the [[TheUnpronounceable hard-to-pronounce]] Machairodontines, or more simply the Machairodonts, named after ''Machairodus''; thus, the name "saber-toothed tiger" (much more rarely, "saber-toothed lion") popularly applied to these creatures is not correct at all. The "tiger" thing has led to them being shown roaring with the same sound as an actual tiger or a lion, though only the big cats of the genus ''[[PantheraAwesome Panthera]]'' (that is, lions, tigers, jaguars and leopards) can produce such a roar thanks to the structure of their larynxes, which is unique to this genus. Although the structure of the small bones in sabertooths' throats were set up for roaring, it's uncertain if these roars were identical to that of modern big cats.

In media, ''Smilodon''s will also probably use their sabers for every conceivable task, like slaying herbivores the size of mastodons or ''Megatherium'' with a single stab, despite the fact that most real sabertooths (as well as their relatives, the [[UsefulNotes/PrehistoricLifeMammals scimitar-tooths and dirk-tooths]]) had relatively delicate fangs that could not safely be used for stabbing. Instead, they probably slashed out the throats of prey from below. And they may be depicted as striped or spotted, just like a ''literal'' tiger or other big cats, which isn't completely impossible, but like the roar, there isn't concrete proof of all this: soft tissue of skin has not been preserved in the tarpits in which smilodons have been found in large numbers (hundreds of individuals in California).

All the story of scientific hyps about the fangs and their usage in life recalls the one made across the years about the claws of the dinosaurs named "raptors" - which incidentally and parallelly, have also been exaggeratedly portrayed as killers of immense prey, sometimes even painted in stripes or spots like felines when they were still believed featherless.

Expect to see ''Smilodon'', ''Machairodus'' etc. frequently interacting with humans, as our ancestors' main predators; in RealLife other carnivores such as the aforementioned prehistoric lions were probably more common predators of early humans. And expect to see them [[SnowySabertooths living alongside woolly mammoths]]. Even though they were contemporary, their habitats in RealLife were largely different, with ''Smilodon'' preferring warmer climates, though ''S. fatalis'' would have experienced snowy winters considering its region's climate at the time. Neither species of ''Smilodon'' lived at the far northern latitudes where woolly mammoths were found, though other saber-toothed cats such as ''Homotherium'' did. And, in less serious works, don't rule out seeing saber-toothed cats somehow living alongside dinosaurs, and in the worst-case scenario, [[NinjaPirateZombieRobot fighting against a ''T. rex'']].

In RealLife, ''Smilodon'' was an animal exclusive to the Americas (the New World), filling the niche the other sabertooths, ''Machairodus'' for example, were occupying in the Old World (Europe, Asia, Africa). ''Smilodon'' and kin were among the most specialized members of the Carnivoran order of mammals. Its hindlegs were shorter than its forelegs, like hyenas and some bears, and a stubby tail; it was powerful but quite slow-moving, and agile only in a straight line: in other words, a sort of MightyGlacier. The lower jaws were more gracile than modern big cats', and had a loose hinge that allowed them to open incredibly wide convergently with hippos, but were not apt for delivering powerful crushing bites, similar to snakes' jaws (venomous snakes have often upper fangs surprisingly similar to a sabertooth's). ''Smilodon'' had the biggest/longest fangs among all saber-toothed cats; this, together with its body size, might explain why it's become the most famous member of the group (and often cited as THE sabertooth ''par excellence''). Only the earlier, distantly-related pseudo-cat ''Eusmilus'' had fangs of comparable size.

The "sabers" of ''Smilodon'' were arguably used only for slashing the throat of prey that had already been subdued with its bodybuilder-like forearms; the molars and lower canines were smaller than those of modern cats but the incisors were bigger, and more apt than the canines for tearing off flesh from its preys' bodies. ''Smilodon'' is often portrayed living in wolf-like packs with both sexes actively hunting, though this is considered controversial by some scientists as there is not enough actual evidence to support it. Some artists have even depicted smilodonts with a totally speculative [[PantheraAwesome lion mane]], linked with the pack behavior which is practiced by lions but unusual for other modern felines. The modern feline with the longest fangs today in respect to the body is the smallish "clouded leopard" (''Neofelis'') of Asia; the one with the bulkiest body-frame is the larger jaguar (''Panthera onca'') of the Americas. The overall biggest modern feline is ''Panthera tigris altaica'', the Siberian Tiger, with some individuals as big as extinct cave lions or American lions.

Saber-toothed cats went extinct 10,000 years ago, after the Ice Age ended. Like the mammoths, [[WildMassGuessing theories have been raised]] as to how they died off, such as due to climate change thanks to the end of the Ice Age, the lack of big prey for them to hunt, or humans changing their habitat by setting fires, killing off their food supply. Anyway, it's certain that they didn't evolve into modern cats, because as mentioned above, they were from a distinct cat lineage from modern felines.

One of the largest and most spectacular land mammals that ever lived, ''Megatherium americanum'' was the same size as an elephant or a ''T. rex'': it reached 5m when standing fully erect, like a giraffe but much heavier. Indeed, the name "''Megatherium''" means... well... [[ExactlyWhatItSaysOnTheTin big beast]].

In old reconstructions, ''Megatherium'' was shown with a horse-like head and sometimes a giraffe-like tongue to reach foliage on the tree tops. The horse head and giraffe tongue are probably mere fantasies, but the high-browsing habits aren't; indeed, the robustness of its body allowed it to stand on only its hind feet - which, curiously, had only one claw each, and were not flat on the ground but facing to each other like an orangutan's feet - and on its robust tail like a tripod, while the three-clawed, bear-like forefeet were used to pull down branches, like what is thought about the large, convergently-shaped [[UsefulNotes/StockDinosaursSaurischianDinosaurs therizinosaur dinosaurs]]. When quadruped, ''Megatherium'' probably knuckle-walked with its forelimbs like a modern giant anteater (''Myrmecophaga tridactyla'').

Actually, our "big beast" was neither a horse nor a giraffe relative, nor was it a giant bear... it was a ''sloth''. More precisely, the stock animal within the group called giant ground sloths, which are not only related to modern sloths, but also to anteaters and armadillos, and ''not'' to ungulates or carnivores. The most famous pictures of ''Megatherium'' show it with fur, like a modern sloth, and to some extent this has been validated by fossilized hair imprints from other ground sloth species. However, there is also speculation that ''Megatherium'' was hairless, much like an elephant or rhinoceros. It probably gave birth to one offspring per time, like modern sloths and anteaters, but the length of its gestation can only be guessed.

An extremely controversial idea is that ground sloths might have supplemented their diet with ''meat'' that they scavenged from predators such as sabertooths by chasing them away from their kill. There isn't much to support this theory other than RuleOfCool, though. It is entirely possible they may have eaten ''some'' meat, since modern herbivores like deer have been known to do so for protein and because it's easier to digest. However, this would not be a natural part of their diet, and they would more likely prefer plants. This didn't stop ''Series/WalkingWithBeasts'' from depicting ''Megatherium'' chasing some ''Smilodon''s away from their kill and eating it, and since then, it has been forever cemented as an omnivore in video games such as ''VideoGame/ZooTycoon'' and ''VideoGame/ArkSurvivalEvolved'' [[note]]The former for being able to eat meat placed in its exhibit, though the animal itself rarely attacks other animals in the game (applying to its portrayal in ''Zoo Tycoon 2'', in ''Zoo Tycoon 1'', food is planted by the staff rather than the player, so the staff only provided plant foods in the first game, whereas the second game added more options, unusual enough compared to its reared up posture becoming its default posture in the game), the latter putting a more realistic interpretation of its carnivory by leaning it closer to being an insectivore like anteaters and armadillos, going berserk in the presence of insects and regularly attacking them, but otherwise the design is actually one of the most accurate models in the game.[[/note]] Some portrayals take this depiction up to eleven by having it be an ''active hunter'', knocking over animals like the tank-like glyptodonts to tear open their soft belly, almost like it was a mammalian version of ''Tyrannosaurus rex''.

''Megatherium'' is the most well-known species of ground sloth, due to [[BiggerIsBetter being the largest]]. Like ''Smilodon'', it's commonly depicted [[MisplacedWildlife alongside the aforementioned mammoths]], despite being strictly South American (mammoths never reached this continent). The proboscideans that ''did'' reach South America, such as ''Cuvieronius'', ''Notiomastodon'', and ''Stegomastodon'', are classified as gomphotheres, a primitive family more closely related to elephants and mammoths than mastodons were, but modern research has begun to reconsider them as mastodons (with the gomphothere family becoming a wastebucket taxon). Different sloth species that reached North America, such as ''Nothrotheriops'' and ''Megalonyx'' below, would've been the ones contemporary with mammoths and the American mastodon.

''[[http://en.wikipedia.org/wiki/Megalonyx Megalonyx]]'' was the sloth species that was common in North America, but it was about half the size of its more famous cousin. It was first described, believe it or not, by president Thomas Jefferson! Since the existence of prehistoric life was still controversial at the time, he believed that the original claw of ''Megalonyx'' ("big nail") could have been from a still-existing mysterious lion in North America. Among "small" ground sloths of South America, ''[[UsefulNotes/PrehistoricLifeMammals Mylodon]]'' is frequently found in caves like ''Megatherium''.

The most famous ground sloth in fiction is Sid from the ''WesternAnimation/IceAge'' franchise, who is only about the size of a human, and resembles ''no'' ground sloth in real life, much less ''Megatherium''. He looks more like a modern tree sloth, which the animators did indeed model him off of, but with bizarre protruding eyes. In prehistoric terms, he seems to be closest to the ''[[http://en.wikipedia.org/wiki/Nothrotheriops Nothrotheriops]]'' (or Shasta ground sloth) at least in terms of appearance. The most improbable portrayal of these critters would have to be in the 1948 B-movie ''Film/UnknownIsland'', where a ground sloth was depicted as a strange, roaring predator that resembles [[MixAndMatchCritter a cross between a gorilla and a bear]].

Mammoths weren't the only "woolly" creatures that lived in the Ice Age. Special mention should be given to the slightly less famous but still notable woolly rhinos, the "ceratopsids" of their time, and possibly subject of RhinoRampage.

''Elasmotherium sibiricum'' ("Siberian thin-plate beast"), also known as the unicorn rhino, is probably the biggest true rhinoceros known: it's often confused with the proper woolly rhino (''Coelodonta antiquitatis'', "hollow tooth of antiquity") because of their similar appearance. However, the latter was no larger than modern white rhinos and had ''two'' horns as well; it was closely related to the modern [[http://en.wikipedia.org/wiki/Dicerorhinus_sumatrensis Sumatran Rhinoceros]], the smallest extant rhino species (and the only one with some hair on its body). ''Elasmotherium'' was much larger (5 tons, like a modern bush elephant) and with a single horn... on its ''forehead'' rather than its nose, and perhaps as long as a grown man; hence [[ExactlyWhatItSaysOnTheTin unicorn rhinoceros]]. It was not closely related to any of the five modern rhinoceros species, but still belonged to the rhino family, the Rhinocerotidae.

Both rhinos lived in the Ice Age in cold climates, alongside mammoths in northern Asia, but the elasmothere had a more southerly range than the proper woolly rhino, and while both lived east of the Urals, only ''Coelodonta'' was found in Europe (there is, however, a cave painting that might stretch ''Elasmotherium'''s range as far as France); the woolly rhino ''Coelodonta'' lived alongside the other, more popular woolly ([[MammothsMeanIceAge guess what]]) in the same frozen landscapes. Interestingly, both the elephantine "woolly" and the rhinocerotine one (we're always talking about ''Coelodonta'') have left soft parts of their bodies other than bones and teeth: hair and horns included.

It's important to note that rhino's horns are ''not'' made of bone like the horns of bovids and deer, but of ''hardened hair'', and don't usually preserve as fossils. The anterior curved horn of the proper woolly rhinoceros was laterally flattened, and some have speculated it used it to free the terrain from snow to reach the vegetation below, like modern caribous do with their hooves and antlers (and like woolly mammoths may have done with their tusks). The coelodonta had also a hump on its shoulders like a bison, and nostrils curving downwards.

Unlike the woolly rhino, we don't know what size and shape the elasmothere's horn actually was, because it has never found. Traditionally, it's been believed that it was enormous, possibly the longest horn in the animal kingdom. More recently, though, it's been suggested that the elasmothere's horn was actually short and blunt, something along the lines of the modern-day [[https://en.wikipedia.org/wiki/Javan_rhinoceros Javan rhinoceros]]-- in which case ''Elasmotherium'' might not have been the "prehistoric unicorn" it is often imagined to be. Both rhinos had three toes for each foot like the modern ones, and probably reproduced in the same manner, giving birth to one (hornless) calf after a very long gestation, like modern rhinoceroses but unlike hippopotamuses, whose pregnancy is rather short for their size (8 months). Both rhinoceroses went extinct without leaving descendants.

The "unicorn rhinoceros" is often thought to have been the inspiration for the {{Unicorn}} myths found all over Eurasia in one form or another when still alive, but this is mere speculation. There's a chance the unicorn rhino might have lived into historic times, but the anecdotes and depictions of these creatures might just as well refer to one-horned bulls or animals frozen in the permafrost like mammoths are known to have been. Once again, it appears humans did these creatures in just as things were getting better.

Mammoths and mastodons often show up in anything dealing with prehistory: you can even see them living [[https://youtu.be/bENtOFR66YY in tropical volcano-filled worlds alongside dinosaurs]], but thankfully mammoths are usually [[MammothsMeanIceAge associated with the Ice Ages]]. It's hard to imagine a prehistoric icy landscape without a curly-tusked mammoth wandering in.

The species most commonly portrayed of mammoth is by far ''Mammuthus primigenius'' (lit. "primeval mammoth"), better-known as the woolly mammoth, or THE mammoth ''par excellence''. Probably the most iconic non-dino prehistoric animal of all, thanks to its resemblance to an elephant with huge curly tusks and dense hair, but also to the countless, extraordinarily well-preserved specimens with soft tissues found both in northern Eurasia and northern North America. These findings have long made it one of the most accurately-portrayed of all prehistoric animals, and one of the very rare extinct animals almost as scientifically well-known as a still-living animal. However, the real cause of its extinction during the Pleistocene epoch [[WildMassGuessing remains unclear]], as is [[WildMassGuessing the precise meaning]] of the word "mammoth", which is of Russian origins. The animal is known as ''Mammouth'' in French, ''Mamut'' in Spanish and Polish, ''Mammut'' in German and Italian, ''Mammoet'' in Dutch, ''Mamute'' in Portuguese, and so on.

Despite its familiarity, even this animal is not spared misconceptions and mistakes in its portrayals. The most common error is thinking the woolly mammoth was ''larger'' than modern elephants: actually the "woolly" was the same size as its tropical, 21st-century cousins — perhaps this is due to the confusion with other mammoth species that ''were'' a bit larger, like the Columbian or Imperial mammoth (''Mammuthus columbi''). Also note that only males had the typical huge, curled tusks; the females' tusks were not that different from those of modern elephants. As preserved fossil hair is often rich reddish-brown, some depictions show woollies with this color; actually, this is due to a chemical change in the hair during the intervening thousands of years. When alive their hair could be black, as seen in both ''Series/WalkingWithBeasts'' and ''Series/PrehistoricPark'', or more rarely, pale "ginger" or even blond. The last notion comes from a genetic analysis made in 2006 on a sample.

It's worth noting that mammoths, scientifically speaking, were just another genus of elephant, since they belonged to the same family, the Elephantidae. The Asian elephant (''Elephas maximus'') is slightly more closely related to mammoths (''Mammuthus'') than to its more distant modern African relatives (''Loxodonta africana'' and ''Loxodonta cyclotis'') — thus mammoths (and mastodons) ''weren't'' the direct ancestors of elephants as is sometimes claimed. Closely related to the several ''Mammuthus'' species were the members of the genus ''Palaeoloxodon'', the "straight-tusked elephants"; the best-known of them is ''[[http://en.wikipedia.org/wiki/Palaeoloxodon_antiquus Palaeoloxodon antiquus]]''. This was an elephantid of the Ice Ages, but living in warmer climates, bigger than the woolly mammoth and about the same size as the Columbian mammoth. Other recently-extinct elephantids underwent a high degree of insular dwarfism, some becoming as small as an average sheep or pig.

On the other hand, the proper mastodons (whose common name curiously means "breast-tooth") were ''not'' true elephants, but just distant relatives of both mammoths and surviving elephants, and were much more primitive within the phylogenetic tree than the Elephantidae. The scientific name of the commonly-known species of mastodon, ''Mammut americanum'', is partially misleading: it was American indeed, but not a mammoth, and had shorter limbs and a couple of small teeth in the lower jaw, unlike true mammoths. Other species of the genus ''Mammut'' lived in Eurasia in the same period.

Like the woolly mammoth, the American mastodon has left exquisite remains (such as those in the Californian tarpits). It lived during the Ice Ages, but in warmer climates than ''Mammuthus primigenius'', and was neighbour and possible prey of the sabertooth ''Smilodon fatalis''. Interestingly, in some languages the adjective "mastodontic" or "mastodonic" has become a household word as a synonym of "huge," "enormous," like the usage of "mammoth" as an adjective with the same meaning (see the nickname "mammoth-tree" for redwood trees or sequoia trees) but the animal wasn't actually that big compared with other extinct proboscideans: the American mastodon was a bit smaller than a bush elephant. Also worthy of note is that at the start of the Palaeontology in the late 1700 the word "mammoth" was often used to indicate the mastodon, or vice versa: sadly, some confusion still exists today in media and common speech.

For other extinct elephant relatives, see some entries below and
[[UsefulNotes/PrehistoricLifeMammals Prehistoric Life]]. Many of them are called "mastodons" or "mastodonts" in classic paleozoology, ex. ''Platybelodon'', the "shovel-toothed mastodon", and ''Anancus'', the "European mastodon", but they were not strictly related with the genus ''Mammut''; recent cladistics show the latter was actually more primitive than the other "mastodonts", and they don't form a distinct family or a true clade like the Elephantids do.

#'''Entry Time:''' N/A for the woolly mammoth, which has been a cultural icon since prehistory. 1864 for the american mastodon.
#'''TropeMaker:''' ''Literature/JourneyToTheCenterOfTheEarth'' (Mastodon)

Even prehistoric ''mammals'' are sometimes mislabeled dinosaurs. Colloquially, this is often true of prehistoric amphibians or even prehistoric fish and invertebrates, and also existing critters that are considered "living fossils" (the coelacanth, tuatara, horseshoe crab, nautilus, etc.), and mammals that went extinct after the dawn of recorded history. Only birds, whether they went extinct before recorded history or afterward, are ''not'' mislabeled when called dinosaurs.

Among mammals, those living in the Ice Age have classically been the most portrayed, because they lived alongside the most iconic hominins ([[AllCavemenWereNeanderthals Neanderthals]] and Cro-Magnons). But earlier mammals of the Cenozoic Era (the Mammal Age) occasionally appear, usually — needless to say — the [[RuleOfCool coolest-looking]] among them.

Portrayals of [[https://youtu.be/AtVGwHPzyNc prehistoric mammals]] have usually been more accurate than those of prehistoric reptiles since large extinct mammals both have left more numerous remains than the latter, and are easier to "bring to life" correctly in media by comparing directly them with their modern relatives — though this doesn't entirely prevent inaccurate reconstructions. A good percentage of them received an increase in popularity just after the TurnOfTheMillennium thanks to ''Series/WalkingWithBeasts'' and [[WesternAnimation/IceAge CGI cartoons]], but others (especially the Ice Age ones) have been popular since long before then.

!! The Symbol of the Ice Age: the [[http://en.wikipedia.org/wiki/Woolly_mammoth Woolly Mammoth]] & the [[http://en.wikipedia.org/wiki/Mastodon American Mastodon]] ***

''Moschops''' teeth were small and blunt, and all rather similar to each other, unlike most other synapsids (''Dimetrodon'' included), but they were enough for taking vegetation of the harsh landscapes it inhabited. It lived in Middle Permian South Africa (hence the species name ''capensis''); some portrayals wrongly show it living alongside ''Dimetrodon'' or ''Cynognathus'', but it actually lived in a time period between the two, later than the former and earlier than the latter. Old sources often wrongly depicted ''Moschops'' with reptilian scales (a common error with most mammal-ancestors), and even with an erroneous line of reptilian tubercles along its neck, back and tail (a bit like an iguana crest but blunter). We don't know if it had some hair on its body like ''Cynognathus'' above or was naked-skinned like a modern rhinoceros. Like the tuatara, it had a "third eye" at the top of its skull; in actuality, a tiny bunch of light-sensitive cells properly called the "pineal eye". ''Moschops'' was also the eponymous star of the British stop-motion animated kids show ''Moschops'', depicted as being best friends with an ''Allosaurus'' named [[ALizardNameLiz Ally]] and living with his Grandfather Diplodocus and Uncle Rex; neighbors included Mr. Icthyosaurus and Mrs. Kerry the ''Triceratops'' -- not the most scientifically vigorous show by any stretch of the imagination (the title character didn't even look anything like a real 'Moschops''!).

''Moschops''' teeth were small and blunt, and all rather similar to each other, unlike most other synapsids (''Dimetrodon'' included), but they were enough for taking vegetation of the harsh landscapes it inhabited. It lived in Middle Permian South Africa (hence the species name ''capensis''); some portrayals wrongly show it living alongside ''Dimetrodon'' or ''Cynognathus'', but it actually lived in a time period between the two, later than the former and earlier than the latter. Old sources often wrongly depicted ''Moschops'' with reptilian scales (a common error with most mammal-ancestors), and even with an erroneous line of reptilian tubercles along its neck, back and tail (a bit like an iguana crest but blunter). We don't know if it had some hair on its body like ''Cynognathus'' above or was naked-skinned like a modern rhinoceros. Like the tuatara, it had a "third eye" at the top of its skull; in actuality, a tiny bunch of light-sensitive cells properly called the "pineal eye".

''Dimetrodon'' was probably the top predator of its time and one of the first large terrestrial predatory vertebrates, shown in paleo-art hunting early amphibians like ''Eryops'', ''Diplocaulus, and ''Seymouria''; fish; and what could be called its Non-Identical Twin, '' Edaphosaurus'' (see below). Its crest, its deceptively reptilian appearance, and the fact that it was a large carnivore make ''Dimetrodon'' a predestined victim of DinosaursAreDragons and PrehistoricMonster both in fiction and in docu-media. However, if you put it next to other famous prehistoric animals, ''Dimetrodon'' would appear rather [[{{Narm}} narmy]]. If we imagine a battle against a ''Tyrannosaurus'', ''Deinosuchus'', ''Smilodon'' or ''Mosasaurus'', the primitive and relatively small dimetrodont would always be the loser -- this might also be true if it were pitted against modern predators (lions, tigers, Kodiak bears, polar bears, Nile crocodiles, great whites sharks, killer and sperm whales, etc.), as well as most ancient and modern giant herbivores, like the multi-ton sauropods, elephants, mammoths, trikes, stegos, rhinos, hippos etc. Its weakest point, other than the primitive gait, would be its blood-vessels-rich membranous sail, bleeding copiously to death if ripped off by its animal adversary. But in the Early Permian swamps it called home, ''Dimetrodon'' was still the fiercest and most powerful carnivore of its time, definitively debunking the {{Narm}} thing.

!Mammal-like "Reptiles"

Most non-mammalian synapsids lived well before the appearance of the first dinosaur during the Permian period (just before the Triassic); indeed, non-mammalian synapsids were the very first large land vertebrates and diversified much during their time on Earth, until most of them were wiped out in the huge Permian mass extinction. In the new world that followed, the few surviving species were progressively outcompeted by archosaurs, the group containing dinosaurs, pterosaurs and crocodilians. The last kinds were depleted at the end of the Triassic in another mass extinction, with their true mammalian descendants continuing their legacy. They are traditionally divided into the more derived therapsids and the more basal "pelycosaurs", with mammals technically being members of the former group in the same way birds are theropod dinosaurs. Although popularly called "mammal-like reptiles", they're not related to any reptiles living or extinct and should be more properly called proto-mammals, mammal-ancestors, or stem-mammals.

Even though it was almost certainly hairy, ''Cynognathus''' fur would have been less dense than modern mammals. Unlike ''Dimetrodon'', ''Cynognathus'' has never been portrayed with scaly hide; at most, it's given just naked skin. We don’t know if ''Cynognathus'' and other cynodonts had external ears or mammary glands (two distinctive mammalian traits), but the odds they had them were obviously far greater than the primitive ''Dimetrodon''. Like the latter, we have no idea how ''Cynognathus'' was colored. Media tend to depict cynodonts like it and ''Thrinaxodon'' (and other carnivorous therapsids like the apparently-similar but more primitive gorgonopsids) with a [[RealIsBrown brown color scheme]], but this might not have been the case in RealLife. The usually-bland coloration typical of mammals is thought to be an adaptation for darkness -- according to scientists, every modern mammal (even diurnal ones, like us humans) descend from night-dwellers. Nocturnal habits, however, developed within the synapsid lineage only in the Triassic, to avoid competition with dinosaurs (or at least, that’s what most scientists say). If true, this would mean non-mammalian therapsids like ''Cynognathus'' could have been very colorful, like many modern reptiles and birds.

''Moschops'' ("calf's face") is the most famous member of a peculiar subgroup of basal therapsids: the Dinocephalians, "terrible heads", much more primitive than the cynodonts like ''Cynognathus'' and also more basal than dicynodonts like ''Lystrosaurus''. It was one of the biggest among all mammal-ancestors as well (the size of a small rhino), making even the biggest ''Dimetrodon'' species small in comparison — but was still much smaller than the most popular dinosaurs.

''Moschops capensis'' (the name of the classic species) was characterized by powerful front legs longer than its hind legs: this, combined with its massive chest and muscular neck, gave to it a rather [[ComicBook/TheIncredibleHulk Hulky frame]]. It had also partially splayed front limbs, more erect hind limbs, and a short but well-developed tail. Even though little-visible in a mount or painting, the most specialized trait of ''Moschops'' is the thickened skull roof, a bit like that of a giraffe but without the "horns" of the latter (its relative ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Estemmenosuchus]]'' had some horn-like protrusions). The purpose of its hard head is not known: headbutting rivals or predators is a possibility (like a giraffe indeed), making it sort of an earlier version of the true dinosaur ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Pachycephalosaurus]]'', but it could alternatively just have been for display.

''Moschops''' teeth were small and blunt, and all rather similar to each other, unlike most other synapsids (''Dimetrodon'' included), but they were enough for taking vegetation of the harsh landscapes it inhabited. It lived in Middle Permian South Africa (hence the species name ''capensis''); some portrayals wrongly show it living alongside ''Dimetrodon'' or ''Cynognathus'', but it actually lived in a time period between the two, later than the former and earlier than the latter.

Old sources often wrongly depicted ''Moschops'' with reptilian scales (like most mammal-ancestors), and even with an erroneous line of reptilian tubercles along its neck, back and tail (a bit like an iguana crest but blunter). We don't know if it had some hair on its body like ''Cynognathus'' above or was naked-skinned like a modern rhinoceros. It's sometimes said to have had a "third eye" in the middle of its skull; actually this "eye" was just a tiny bunch of light-sensitive cells shared by many other primitive vertebrates (such as the modern tuatara).

Described only in 2019 (at the end of TheNewTens), ''Lisowicia bojani'' was found in Europe, precisely in Poland near the town of Lisowice -- hence the name. It's not only the last confirmed dicynodont known, living at the very end of the Triassic (even later than the former record-holder, ''Placerias''); reaching the size of a ''modern elephant'', it is now by far the biggest known "mammal-like reptile" ever, as heavy as the biggest contemporaneous "prosauropods" like ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Riojasaurus]]'' but still half the length and height of them because of the absence of the typically long neck and tail of the sauropods and their relatives.

Marking its similarity with an elephant even more, ''Lisowicia'' had also erect pillar-like limbs convergently like a proper dinosaur or elephant, not splayed like most other mammal-predecessors of the Triassic. And had elephantine feet, and unusually for a mammal-ancestor also almost-lacked external tail, resembling several true mammals in this. ''Lisowicia'' is destined to gain attention, possibly becoming as common in paleo-books as other more traditional therapsids.

The gorgonopsians ("monstrous faces") were the top predators of the Late Permian, but they were killed off by the huge mass extinction that divides the Paleozoic from the Mesozoic. More slender and usually smaller than dinocephalians, they are nicknamed "sabertooth" just like [[PantheraAwesome their mammalian namesakes]]; however their upper canines, though longer than most therapsids, were far less developed than those of a saber-toothed cat. They include the prototypical ''Gorgonops'', the wolf-sized ''Lycaenops'' ("wolf face") and ''Sauroctonus'', but the perhaps most portrayed has been (of course) a larger genus, the cow-sized ''Inostrancevia''. It is named after a Russian geologist, and is perhaps the biggest of the whole group. The type species is ''Inostrancevia alexandri''.

Gorgonopsians, ''Cynognathus'' and other carnivorous therapsids are often described as [[AllAnimalsAreDogs looking like dogs]]; indeed, in modern depictions, this resemblance is even more evident than in the older, more reptilian portraits. As usual for synapsids, whether or not the gorgonopsids laid eggs and/or had mammary glands is still unknown.

The gorgonopsids' history in pop culture is convoluted. The Czech paleoartist Zdenek Burian first depicted a ''Sauroctonus'' interacting with a ''Scutosaurus'' [[https://i.pinimg.com/originals/45/38/30/45383040e2067086741fd593d84c48e7.jpg in one of his old paintings]] and they have appeared seldomly in educational books. The second ''VideoGame/DinoCrisis'' game included ''Inostrancevia'', [[ArtisticLicensePaleontology inaccurately showing it as an armored monster living in volcanoes alongside Jurassic and Cretaceous-period animals]]. The {{Series/Primeval}} series made them famous by having ''Inostrancevia'' appear in the first episode, while BBC's documentary series ''Series/WalkingWithMonsters'' included the eponymous ''Gorgonops'' in the third and final episode, enlarged up to the size of ''Inostrancevia''.

# '''TropeMaker:''' ''Series/{{Primeval}}''

!! The First known Mammal-Ancestor: ''[[http://en.wikipedia.org/wiki/Dicynodon Dicynodon]]'' *

The first mammal-like "reptile" ever described was ''Dicynodon lacerticeps'' ("lizard-headed two dog-like teeth") in the middle of the XIX century, the time in which Darwin popularized his revolutionary concept of evolution.

His pupil Thomas Huxley (nicknamed "[[AngryGuardDog Darwin’s Mastiff]]") proposed a surprisingly modern hypothesis, that land vertebrates should be divided in only ''two'' branches instead of the Linnaean tripartition mammals-birds-reptiles. These lineages were: ther'''o'''psids ("beast-looking", not to confound with ther'''a'''psids) and sauropsids ("lizard-looking"). The former were basically the mammals; the latter were the reptiles (including dinosaurs ''and'' birds). Since ''Dicynodon'' was initially not thought a mammal ancestor, in Huxley’s classification it was put in the "sauropsid" branch. This was the start of the tradition to classify these animals as reptiles, and to depict them with reptilian traits. Even though the relationship therapsid-mammal was cleared at the start of the 20th century, the mammal-like "reptiles" thing has endured until the 21th century.

''Dicynodon'' lived in Late Permian Southern Africa, and is the official prototype of the Dicynodont subgroup of therapsids. Lived in Late Permian, before ''Lystrosaurus'', was relatively small-sized compared with the latter, but with the usual only-two-toothed dentition of the group. Due to the earliness of its discovery it is also the only mammal-ancestor portrayed in the Crystal Palace Park of London -- with oversized upper "canines" and, worse, with a totally erroneous turtle-shell.