The following prehistoric animals, to quote Lore Sjoberg, "are not technically speaking dinosaurs but end up in the dinosaur section of the plush toy aisle nonetheless."
This can get quite confusing, as no matter what your dictionary tells you, scientists have been waffling on the subject of dinosaurs for as long as there has been a name for them.


!Flying reptiles

[[ Pterosaurs]] (usually called pterodactyls in media and in pop language) are often referred as the "flying dinosaurs". They were closely related to them, but were not true dinosaurs.

[[folder:Pterosaurs in media]]

In RealLife, pterosaurs were the main flying beings in the Age of Dinosaurs, coexisted with their land-dwelling relatives for 160 million years and eventually went extinct together with the last dinosaurs. As with dinosaurs, there are several issues about pterosaur portrayals in media. They go much further than simple AnachronismStew and MisplacedWildlife, they regard ''every'' pterosaurian biological feature. Here, it’s easy to imagine [[ArtisticLicensePaleontology pterosaur scientists crying more than every other colleague]].

* In fiction, these "reptiles" usually act as [[GiantFlyer airborne terrors]] to menace humans and/or other animals, usually grabbing them with improbable eagle-like feet and magically strong enough to lift and carry their victims in flight, often giving them to their nestlings just like eagles. In RealLife pterosaurs had very weak legs with non-opposable digits and caught their food with their mouths instead. And they didn't have any nestlings to feed: pterosaurs reproduced like lizards, burying and abandoning their soft eggs, until the hatchlings (termed "flaplings" by some paleontologists) emerged, strong-boned and ready to fly on their own.
* Especially in older media, they are often portayed with [[MixAndmatchCritter Bat Wings]], tying into the whole DinosaursAreDragons thing. Actually their wing membranes were sustained by ''only one'' overly-long digit, the fourth one (not the fifth as sometimes shown), which was as robust as the rest of the forelimb. The first, second and third fingers were normal-sized and protruded from the anterior wing-edge like the first digit of modern bats. More persistent is the depiction of the wings as loose, bat-like flaps of skin — in RealLife, the wing membranes were thin but taut sheets of muscle, containing several distinct layers of complex muscle fibers which essentially made them into shape-shifting organs for on-the-fly adjustments.
* We don’t know at all which kind of sounds they emitted in RealLife, but expect to hear them [[NoisyNature screeching loudly and continuously]] (usually in a mixed crow-vulture-seagull manner), and also fanning their wings as noisily as possible.
* They tend to be represented ''always'' huge. In RealLife there were ''many'' types of pterosaurs (just like modern birds) and they were astonishingly diverse in size, being from the size of a crow up to a small airplane.
* They weren't dinosaurs, nor were they birds. Further, they were not even the ancestors of any modern flier[[note]]dinosaurs were the ancestors of birds; synapsids (below), being the ancestors of ''all'' mammals, were the ancestors of modern bats, and invertebrates aren't even worth mentioning in this note[[/note]]: instead, they were only ''relatives'' of dinosaurs (and thus birds, of course).

Its worth noting, however, that ScienceMarchesOn has been a crucial factor in pterosaur portrayals. Like dinosaurs, pterosaurs have undergone a sort of scientific "renaissance" since the seventies. Before that, they were considered cold-blooded creatures covered in scales and very unlike modern birds. Scientists used to think pterosaurs had weak wing muscles and fragile wing membranes; this made the RealLife pterosaurs qualified as awkward gliders — contrasting with the "powerful flyers" popular view. Since the "renaissance" palaeontologists have upgraded these animals as "the first ever vertebrates able to fly properly", and nowadays it's clear they were active and efficient fliers with large brains, good eyesight, excellent sense of balance, skin covered in down-like structures (just like the most bird-like theropods), and with high-rate metabolism. Due to the structure of their wings pterosaurs should be particularly able in soaring (a bit like modern albatrosses), but were also able to flap their wings.

Most discovered pterosaurs appear to have lived in marine, coastal, or other watery habitats, but more dryland-loving kinds surely existed as well: some of the smallest species were probably able to climb trees. They were mainly predators of small prey (insects, fish, small land vertebrates etc. according to the species), but some could have been fruit-eaters. Some (especially ''Pterodaustro'') were flamingo-like filter feeders. Like dinosaurs, we don't know what coloration they had: different kinds of pterosaurs surely had different colors. Modern artists can depict them with motifs reminescent of those of modern birds, but may also portray them with duller colors (just like what happens with dinosaurs). The pterosaurs' motion on land has long been a mystery: their footprints have been discovered only since the 1990s, and scientists now think most (if all) pterosaurs were quadrupedal. Despite all these discoveries and theories, even today the pterosaurs remain one of the most enigmatic group of prehistoric beasts, as their fossil record has always been one of the scarcest of all.

Sadly, all the issues above are usually glossed over in pop-media, even today. See PteroSoarer to get into this in depth.

!!Stock Pterosaurs

Very few pterosaurs have been portrayed in non-documentary media, despite their notable variety in RealLife. Among pterosaurs listed here, only three can be called pterodactyls without getting totally wrong: ''Pteranodon'', ''Quetzalcoatlus'', and of course ''[[ExactlyWhatItSaysOnTheTin Pterodactylus]]''. The other two, ''Rhamphorhynchus'' and ''Dimorphodon'', were more primitive than the former and are usually called rhamphorhynchs.

Surprisingly, stock pterosaurs are ''not'' (necessarily) the biggest/coolest-looking ones — three out of five are not bigger than an eagle or a stork. Instead, they were among the very first scientifically-described kinds, in the 19th century. ''Pterodactylus'', ''Rhamphorhynchus'', and ''Dimorphodon'' [[note]]The mid-sized ones[[/note]] were discovered in Europe ''before'' the 1820s (the decade in which the first dinosaurs were named). The last two were initially classified as ''Pterodactylus'' and recognized as distinct only after the 1820s. With its 7m/24ft wingspan, ''Pteranodon'' was found in the USA in the last quarter of the 19th century, during the "Bone Wars." [[note]]Oddly, it too was initially classified as ''Pterodactylus''.[[/note]] Its sheer size ("Whoa the biggest flier ever!") and its crest soon made it the new iconic pterosaur, and still preserves its status today.

Several interesting new pterosaurs were discovered in the second half of the 20th century, but only one managed to achieve some consideration in media: ''Quetzalcoatlus'', because it was the only one clearly bigger than ''Pteranodon'', and the new "biggest flying animal ever." In the 2000s, ''Ornithocheirus'' gained some popularity as well thanks to a memorable appearance in ''Series/WalkingWithDinosaurs'', but only because was (wrongly) described as [[UpToEleven the biggest flying animal ever existed]]. The others (''Dsungaripterus'', ''Pterodaustro'', ''Tapejara'', ''Eudimorphodon'', ''Sordes'', and so on) were largely ignored outside dino-books and documentaries. If you’re looking for these and other non-stock pterosaurs, see [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles here]].

!! Toothed or toothless? ''[[ Pteranodon]]'' ***

''Pteranodon'' lived 86-84 million years ago on what were then the shorelines of Kansas and other midwestern US states. It had the typical traits of the most evolved pterosaurs, the pterodactyloids a.k.a. "literal pterodactyls." It had an elongated head, weak hindlimbs, only a hint of tail, and very long wings with a huge "wing-finger," while the other digits were very small and maybe almost useless. It was one of the most specialized flying animals that ever lived, but very clumsy on land, where it arguably walked slowly on all fours.

It was thought pteranodonts lived a bit like modern seashore birds, laying their eggs on cliffs and using ascendant winds to take off. However, the takeoff method is now known to have been wrong; rather, pteranodonts, like all pterosaurs, could vault from level ground with their wings. Roosting on cliffs is not entirely unlikely, though. Like the modern albatross, they could have been vagrant or migratory. Contrary to what is sometimes said, ''Pteranodon'' probably didn’t survive enough to see the meteorite — its fossil record ends a dozen million years before the mass extinction. Until 2018, only [[UsefulNotes/PrehistoricLife azhdarchids]] have left fossils from 65 mya: one of them was ''Quetzalcoatlus'' (see below). Findings early in 2018 revealed that pteranodontids and their smaller, more derived relatives the nyctosaurids also reached that point, though ''Pteranodon'' itself still hasn't left any fossils from that time.

The backwards-pointing crest is the most striking feature of ''Pteranodon''. It was laterally flattened in RealLife, but in media expect to see it with a conical shape, often resembling a ''horn''. The real purpose of this crest is still unclear. It is traditionally described as a sort of balancing pole to better balance the long head, or as a rudder to keep it stabilized during flight. However, this doesn’t explain why only males had such a big crest, while the females’ one was extremely shortened. It was once thought long- and short-crested individuals belonged to different species. [[note]]An astounding thing is, short-crested pteranodonts are ''almost never'' shown even in documentary media![[/note]] This bony protrusion could simply be a display device, as is hypothesized as well for ''Stegosaurus''’ plates, ''Triceratops''’ horns and frill, ''Spinosaurus''’ "sail," and so on. This could explain why the males’ one was so big compared with the females.

In popular portrayal, an ever-present mistake is to show ''Pteranodon'' as [[ToothyBird toothy creatures]]. When present, these teeth usually resemble those of the other well-known pterosaur, ''Rhamphorhynchus'' (see below). The fact that the genus’ name ends in ''odon'' (meaning tooth in Greek) could lead people in error, too. Actually, ''odon'' is preceded by the Greek "privative ''a-''" (becoming ''an-'' when followed by a vowel). Thus, ''anodon'' means ''toothless''. (See also ''[[UsefulNotes/PrehistoricLife Ludodactylus]]''.)

In RealLife, ''Pteranodon'' was basically a giant pelican in behaviour. Its long toothless beak was useful to catch fish, and the shape of its lower jaws seem to show a sort of "pouch" to store fish in flight, even though this is not certain. It was once thought that ''Pteranodon'' would snatch fish on the fly with its beak, but now it's believed that it would have dived into the water and swam for food (again, much like a pelican). If alive today, ''Pteranodon'' could not be that dangerous for us folks as shown everywhere in media. Weighing only about 20kg, [[note]]Compared to body size pterosaurs were even lighter than birds, having totally hollow bones like straws. For example, the prehistoric vulture ''Argentavis'' had a similar wingspan to ''Pteranodon'', but is estimated to have weighed 80kg.[[/note]] it was too light to lift a 70kg man up in the air. And even if it could have done so, it certainly didn’t with its weak hindlimbs but with the mouth instead. Finally, since its beak was straight and smooth-edged, a child could easily have got out of it by wriggling.

''Pteranodon''’s nifty crest on its skull, along with the fact that it held the size record for almost a century, has made it THE pterosaur in popular imagination. Its iconic status among pterosaurs coud be partially justified. It’s not only one of the first discovered pterosaurs, but perhaps also the most common in fossil record. Hundreds of specimens are known, while most other pterosaur kinds are much, much rarer, often known from a single individual. The vast majority of pteranodonts belong to the species everyone knows, ''Pteranodon longiceps''.

# '''Entry Time:''' 1925
# '''TropeMaker:''' ''Film/TheLostWorld'' (film)

!! Dragon-tailed fisher: ''[[ Rhamphorhynchus]]'' **

''Rhamphorhynchus'' ("sharp beak") was first found in Germany in the 19th century, and lived in the Late Jurassic in the same location as several other pterosaurs and also ''Archaeopteryx'' and ''Compsognathus''. It was the second named pterosaur after the prototypical ''Pterodactylus'', and the first one known with a long tail. It’s the namesake of the primitive pterosaurs called Rhamphorhynchoids. Like ''Archaeopteryx'', ''Rhamphorhynchus'' has left exquisite remains. Some specimens with prints of wing membranes have been known since the 19th century. It was just these ''Rhamphorhynchus'' that definitively showed pterosaurs were airborne critters, not water-dwelling as believed by some at the time.

''Rhamphorhynchus'' had a wingspan of about 2m/6ft, relatively short wings, a narrow snout slightly pointing upwards, robust hindlimbs, and long tail. Two recognizable traits are the protruding teeth and the diamond-shaped "fin" set vertically on the tip of its tail. As ''Rhamphorhynchus'' lived in coastal lagoons, the teeth were probably apt to either catch fish in flight or catch them by swimming and diving. The typical tailfin was made of soft tissue (it’s known only thanks to prints in the rocks).

''Rhamphorhynchus''’ tail has often been compared with a dragon’s or a devil’s, and the large teeth give it a deceptively "menacing" look (actually it wouldn’t be more dangerous than a gull if alive today). We now know it was covered in hair-like structures like its close relative ''[[UsefulNotes/PrehistoricLife Sordes pilosus]]'' (which just means "[[RuleOfCool hairy devil]].")

Its striking look, the earliness of its discover and the completeness of many remains have contributed to make ''Rhamphorhynchus'' the second most commonly portrayed pterosaur in media — especially older media. In particular, the ''Literature/{{Pellucidar}}'' series features the Mahars - a race of ''psychic'' ''Rhamphorhynchus''. The species has become quite rare today — pterosaurs shown in the most recent movies generally are ''Pteranodon'' or (more often) imaginary Giant Fliers.

Like ''Pteranodon'', ''Rhamphorhynchus'' tends to be portrayed incorrectly in fiction, often as big as a ''Pteranodon'' or even bigger. Another classic mistake is to show rhamphorhynchs with flexible tails (a bit like what happens to "raptors") and sometimes with ''triangular'' fins. Actually their tail was stiffened by bony tendons, and was a steering device during flight. [[note]]It's not yet ruled out that only males had the "fin." If so, this thing could have been for display.[[/note]] Finally, a very [[UndeadHorseTrope Undead Horse]] subtrope is to apply the "devilish" rhamphorhynchoid tail to [[RuleOfCool every other]] [[MixAndMatchCritter pterosaur]], especially ''Pteranodon''. Actually pterodactyloid pterosaurs had stubby tails without distinction.

# '''Entry Time:''' 1940
# '''TropeMaker:''' Disney/{{Fantasia}}

!! Divine beast: ''[[ Quetzalcoatlus]]'' *

This is, for now, the ultimate GiantFlyer among prehistoric animals. Lived in North America at the very end of the Cretaceous 70-65 mya (but some think its distribution was worldwide). ''Quetzalcoatlus'' was discovered in the 1970s in Texas from incomplete remains. Its wingspan was estimated from 10m/35ft up to 16m/50ft, with the lower range being the most likely. [[RuleOfCool Of course]], pop-media have often followed the higher one. This "living airplane" took ''Pteranodon'''s reputation over as "the biggest flier ever" in those years. Its describer named it from an Aztec divinity: Quetzalcoatl, the "feathered snake" (the animal itself is often called "the quetzalcoatl").

''Quetzalcoatlus'' was long described as similar to an upscaled ''Pteranodon''. Indeed, both animals had a long toothless beak and an atrophied tail. Some depictions show ''Quetzalcoatlus'' with a small cranial crest, others show it crestless. Compared to ''Pteranodon'', ''Quetzalcoatlus'' had much longer, stronger hindlimbs, a bigger body, a longer, stiffer neck, and shorter, wider wings with the "hands" closer to the wingtips than to the shoulders. Its diet has long been an enigma (Fish? Small reptiles? Carrion?). In the 2000s, scientists re-studied its anatomy, and today ''Quetzalcoatlus'' is thought to have a mainly terrestrial animal, walking on its four long limbs, and eating small land critters like a stork. [[note]]It's worth noting that the terrestrial hypothesis was already postulated just after the first find, but initially not demonstrated.[[/note]]

The astonishing thing is, in spite of being [[ as tall as a giraffe]] when on land, ''Quetzalcoatlus'' could still ''fly''. Giving its size, it should have been an extremely powerful flier, capable of frequenting several habitats, and maybe even traveling worldwide. An almost-identical relative, ''[[ Hatzegopteryx]]'', was described from Europe in 2002. It was estimated even bigger than ''Quetzalcoatlus'', with a 36 to 39ft wingspan and was probably even more menacing as well, with a more muscular frame and a shorter neck.

Despite their impressiveness, ''Quetzalcoatlus'' has received great attention only in dino-books and documentaries, while is still rare in films and dino-stories. No matter that, with its size and terrestrial habits, it could have been the ''only'' pterosaur potentially dangerous for humans if alive today. A downsized ''Quetzalcoatlus'' flying robot capable of flapping its wing was built in the 1990s, although it did not have the proportions that the animal is now known to have had.

# '''Entry Time:''' 1980s
# '''TropeMaker:''' Documentary media

!! The first named Mesozoic reptile: ''[[ Pterodactylus]]'' *

Rarely will you see any other pterosaur in fiction, but if you do, it will either be ''Pterodactylus'' or ''Dimorphodon''. In the original novel ''Literature/{{The Lost World|1912}}'' (1912), the two scientists argue if the pterosaurs they meet are one of the two. Whatever kind they were, they are enormously oversized — [[UpToEleven even bigger than a Pteranodont]]. In RealLife both were not bigger than a large seagull. In recent stories, ''Pterodactylus'' and ''Dimorphodon'' are rarely portrayed, but are common in documentaristic media due to their historical relevance.

''Pterodactylus'' was the ''first'' fossil recognized by science as belonging to a prehistoric animal completely different to the modern ones (well before the first dinosaurs); this happened in year 1809, when concepts like "extinct" and "antediluvian" (the word "prehistoric" came later) were still highly controversial. Obviously, ''Pterodactylus'' was the very first flying reptile ever found, and even early paleontologists tended to refer to the whole group as 'pterodactyls' long before the name pterosaur was coined; this explains why ''pterodactyl'' has become the stock name of pterosaurs.

Several ''Pterodactylus'' species were recognized in the past. Today only one has remained valid, ''Pterodactylus antiquus'', about the same size of a ''Rhamphorhynchus''. Some alleged ''Pterodactylus'' species were described from individuals no bigger than a sparrow: this led the genus to be described as "one of the tiniest pterosaurs ever." [[ScienceMarchesOn Recent research]] suggests these specimens were actually juveniles, which deceptively resemble miniaturized adults. The fact that newborn pterosaurs were virtually identical to adults is a recent discovery which astonished scientists: none of the extant fliers shows powered flight soon after its birth.

''Pterodactylus'' was one of the first pterodactyloid pterosaurs to appear (Late Jurassic Europe), and shared its habitat with the more archaic ''Rhamphorhynchus''. Its body shape was more similar to a miniaturized pteranodont than to a rhamphorhynch, with long, thin jaws, elongated wings, weak hindlimbs, small "wing-hands," and stubby tail. Usually depicted as a generic-as-it-gets pterosaur, the latest findings show it had a small crest made of skin on the back of its head. Moreover, its apparently generic teeth could have been specialized for something — traditionally described as a fish- or insect-hunter, ''Pterodactylus'' could have been a filter feeder in coastal lagoons (though not so specialized as another relative, ''[[UsefulNotes/PrehistoricLife Pterodaustro]]'') or perhaps a wader/prober like a shorebird.

# '''Entry Time:''' 1852
# '''TropeMaker:''' Crystal Palace Park

!! A toothed toucan: ''[[ Dimorphodon]]'' *

''Dimorphodon'' was a rhamphorhynchoid that lived in Early Jurassic, 190 mya. Found in England, it shared with ''Rhamphorhynchus'' the elongated stiffened tail, but we don't know if it had a "fin." Its more striking trait is its oversized skull, even bigger than the body itself! Despite appearances, the head of ''Dimorphodon'' was lightened by wide openings in the skull, and the animal couldn’t have had trouble lifting it, a bit like modern toucans and hornbills with their beaks.

Its name, "two-shaped teeth," recalls that of the famous ''Dimetrodon'' ("two-measured teeth"). It had [[ExactlyWhatItSaysOnTheTin two kinds of teeth]] (while most pterosaurs had only one or none). Some teeth were bigger and sparse among the smaller ones. With this kind of dentition, the feeding habits of ''Dimorphodon'' have always been matter of speculation. It could have been a fisher, a hunter of small land animals, an insectivore, or all these things. Newer evidence reveals that the latter two were more likely, however, as it has few to no adaptations for fishing, but many for terrestrial hunting and leaf-litter grubbing.

''Dimorphodon'' is often depicted as a frequent flyer (the ''Literature/{{Dinotopia}}'' books even portray it as an InstantMessengerPigeon!), but later research suggests that it was quite the opposite. While ''Dimorphodon'' could fly, it was also rather heavy for such a small animal, making flight rather strenuous for it. It's believed that, like similarly loaded birds, ''Dimorphodon'' would have only flown in times of emergency. Interestingly, this is ''not'' an illustration of ''Dimorphodon's'' primitiveness, as many pterosaurs before it were excellent flyers. This likely means that ''Dimorphodon's'' poor flight ability was actually an evolutionary adaptation.

More archaic than ''Rhamphorhynchus'', ''Dimorphodon'' shows several primitive traits which betray how dinosaurs and pterosaurs were closely related. The three free wing-fingers were strong and large-clawed, not unlike those of a feathered theropod (indeed, its species name, ''macronyx'', means "large claw"). The hindlegs were long and powerful, and the animal was believed to have walked bipedally used its long tail for balance, but this is unlikely. Its stocky skull was more similar to a theropod dinosaur than to a pterosaur, with nasal openings on the tip of the nose (most pterosaurs had nostrils just in front of the eyes). A strange anatomical feature is one elongated digit in each hindfoot, which could have been attached to the wing membrane. If so, the dimorphodont could have used it to better-control the flight, like modern bats do with their feet. More evolved pterosaurs lost this super-toe altogether. Despite its primitive anatomy, ''Dimorphodon'' was fully pterosaur with all the pterosaurian traits. (See also ''[[UsefulNotes/PrehistoricLife Eudimorphodon]]''.)

''Dimorphodon'' doesn't typically appear in the media beyond dinosaur books. However, this might be due for a change with the release of ''Film/JurassicWorld'', which had ''Dimorphodon'' as a featured creature ([[PteroSoarer naturally]] in the [[DeathFromAbove "winged menace"]] role). There's even a toy of it!

# '''Entry Time:''' 1912
# '''TropeMaker:''' ''Literature/{{The Lost World|1912}}''

!!Other pterosaurs
Sorry, these ones aren't here. If you're looking for ''Nyctosaurus'', ''Geosternbergia'', ''Dsungaripterus'', ''Ornithocheirus'', ''Anurognathus'', and others, see [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles here.]]

!Swimming Reptiles

Similarly, these animals are often collectively referred to as "swimming dinosaurs," but this time they were ''not'' close relatives of true dinosaurs; some of them were not even related to each other. There ''were'' aquatic dinosaurs (''Spinosaurus'', for one), not to mention modern-day diving birds such as [[EverythingsBetterWithPenguins penguins]], but none of them were completely marine in the way that these reptiles were.

[[folder:Sea reptiles in media]]

Four main groups of sea reptiles can be recognized in media: plesiosaurs, ichthyosaurs, mosasaurs, and pliosaurs. In RealLife there were other sea-going reptiles in the Mesozoic, but being less impressive than the former, they don’t gain much attention (except for the giant turtle ''Archelon'', that shows up occasionally). As with most prehistoric animals, only the largest will be mentioned from each group: ''Elasmosaurus'' for plesiosaurs, ''Liopleurodon'' for pliosaurs, and ''Tylosaurus'' for mosasaurs — with the exception of the ichthyosaurs. Ichthyosaurs will be represented only by ''Ichthyosaurus'', which was actually small for the group, though that won't stop writers from making it bigger. However, in old media ''Plesiosaurus'' is frequent as well, even though was a very small member of the eponymous group (but don’t worry: it is regularly shown oversized as well).

Interestingly, unlike dinosaurs, marine reptiles were ''already'' well-known to science at the beginning of the 19th century. Their fossil record is overall wealthier and better-preserved than that of the dinosaurs. Significantly, the very ''first'' "antediluvian" reptiles entered in narrative media were not dinosaurs, but the ichthyosaur and the plesiosaur which battle each other in the novel ''Literature/JourneyToTheCenterOfTheEarth'' written by Jules Verne in 1864. Both animals were enormously oversized and depicted in a ''very'' fanciful way: if you read the novel, you'll find them more like MixAndMatchCritter-type [[SeaMonster sea monsters]] than their RealLife counterparts. The "ichthyosaur" is similar to a mixup of whales-crocodiles-dragons-snakes-whatnot, and has not the familiar fish-like shape of a RealLife ''Ichthyosaurus''. The plesiosaur is a bit more realistic, but has a serpentine neck and the shell of a sea turtle. However, some of these errors are due to ScienceMarchesOn, as we’ll se in the single sections below.

Possibly thanks to Verne, the battle between prehistoric marine reptiles has become stock in paleo-art and pop culture, just like its land-based equivalent "Carnivorous vs. Herbivorous Dinosaur." One of the opponents is always a long-necked plesiosaur, while the other may alternate between a mosasaur (known plesiosaur predators), an oversized ''Ichthyosaurus'' (other ichthyosaurs were plesiosaur predators, but not this one), or a pliosaur (graphic RealLife evidence exists in the form of a decapitated plesiosaur). In these portrayals, ichthyosaurs, mosasaurs, and pliosaurs tend to be used indifferently, often confused each other and portrayed as generic "giant swimmers."

Another long-standing cliche makes sea reptiles the pterosaurs' archenemies. You probably have already seen the scene of a "prehistoric leviathan" emerging abruptly from the surface of the sea, grabbing a giant flying reptile with its jaws (the victim is usually ''Pteranodon''), and dragging it underwater to eat it (Creator/DougalDixon once speculated that long-necked plesiosaurs would be specialist seabird/pterosaur hunters if they survived to the present). In RealLife this could be possible only for the biggest mosasaurs and pliosaurs[[note]]and even then, we don't have any evidence that either of these types of animals preyed on pterosaurs; in fact, we have more evidence that large fish, predatory dinosaurs, and marine crocodiles would have fancied a leathery-winged snack[[/note]]. Giant ichthyosaurs did roam the seas, but in their time pterosaurs were still ''very'' small. Even though giant plesiosaurs like ''Elasmosaurus'' could have interacted with giant pterosaurs, their small mouths were unable [[FridgeLogic to swallow whole]] [[GiantFlyer Giant Fliers]] like ''Pteranodon''. ''Pteranodon'' bones have been discovered in the belly of a plesiosaur fossil, but they come from a small, female or juvenile pterosaur, not a gigantic male, and in any case they were probably shaken about before being eaten, or more likely scavenged.

!! Turtles inside a snake's body: [[ Plesiosaurs]] **

Plesiosaurs (more correctly, plesiosauroids) are the most distinctive marine reptiles, and lived worldwide throughout the Mesozoic, 210-65 mya. With their long necks, massive bodies, short tails, small heads, and four paddle-like limbs, their look may recall that of a "flippered brontosaur," but they were actually very different from sauropod dinosaurs. They were carnivorous, like all known marine reptiles. With their small mouths, they arguably ate only small prey, like fish, juvenile reptiles, or shellfish. Their hunting techniques are still a matter of discussion — active hunting, ambush predation, bottom-feeding or even partial filter-feeding are all possible. They had pointed teeth which protruded from their jaws, but were perhaps covered by lips in the living animals. [[RuleOfCool For obvious reasons]], expect to see plesiosaurs with ever-visible teeth fitted outside their mouth, often oversized and more protruding than in RealLife, literally making a snake-like head.

The association with snakes and turtles seems a constant when talking about plesiosaurs. Even scientists once used to describe these animals as "[[MixAndMatchCritter a turtle in a snake’s body]]" or "[[MixAndMatchCritter a snake in a turtle’s body]]." Their bodies were actually turtle-like (except for the lack of a shell, of course), and their necks had a huge number of vertebrae (76 in ''Elasmosaurus''!). Classic depictions show plesiosaurs with extremely flexible necks capable of coiling and darting like a snake. ScienceMarchesOn however, and it was discovered in the 2000s (thanks to simulations in CGI) their necks were much more rigid than previously thought, a bit like what has happened to sauropod dinosaurs.

These animals are traditionally described as slow turtle-like swimmers, using their four flippers as oars and awkwardly propelling their bulk through the water. In classic art, plesiosaurs are usually portrayed in a swan-like posture when surfacing, and often use their necks as periscopes when swimming underwater. According to biomechanical studies, they'd have kept their neck straight to better plough the water, and used their flippers to literally "fly" underwater, even though the exact movement of the flippers is still uncertain (see also the pliosaurs, below). Plesiosaurs may have been among the most skilled swimming animals of all time. Like whales compared to dolphins, larger species may have been less agile than smaller ones. Some portrayals show plesiosaurs with a sort of fin at the end of their tail, but this is only speculative. If present, it acted only as a rudder, as a plesiosaur's tail was too weak to propel the animal.

The most commonly shown species in recent media is ''[[ Elasmosaurus]]'', while ''Plesiosaurus'' is more common in older works. ''Elasmosaurus'' was one of the largest plesiosauroids, 40ft/13m long (about as long as a grey whale), but since only a small portion of its length was the body, it weighed only 8-10 tons (about as heavy as a large killer whale). The 20ft/7m long neck made more than half the entire length, and was actually longer than the body. Living in the Late Cretaceous in the inland Western Interior Seaway of North American, ''Elasmosaurus'' was discovered in the USA during the Bone Wars. Its describer, Edward Cope, made an astounding mistake in his first attempt to rebuild its skeleton by putting the head at the end of the tail (see UsefulNotes/PrehistoricLife). The prototypical ''[[ Plesiosaurus]]'' was the first described plesiosaur (1810s), before even the earliest-discovered dinosaurs, ''Megalosaurus'' and ''Iguanodon''. First found in England, it was much smaller (16ft long), lived earlier (at beginning of the Jurassic) and was proportionally shorter-necked than ''Elasmosaurus''.

Possibly thanks to their dinosaurian look and the association with snakes, plesiosaurs have been the most iconic and depicted sea reptiles in media. Like dinosaurs and pterosaurs, expect to see them as [[PrehistoricMonster scary monsters]] with a [[EverythingTryingToKillYou killing attitude towards humans]]. If alive today, even the biggest ''Elasmosaurus'' wouldn't be more aggressive than most whales (although they could unintentionally capsize your tiny boat or raft). Almost every time a plesiosaur shows up, ''someone'' will bring up the [[StockNessMonster Loch Ness Monster]].

# '''Entry Time:''' 1852 (''Plesiosaurus''); 1933 (''Elasmosaurus'')
# '''TropeMaker:''' Crystal Palace Park (''Plesiosaurus''); ''Film/KingKong1933'' (''Elasmosaurus'')

!! Kron and his (oversized) son: [[ Pliosaurs]] *

The long-necked plesiosauroids belong to the Sauropterygia supergroup, which also includes the pliosaurs (or pliosauroids, so-called from their obscure namesake, ''[[ Pliosaurus]]'') and other lesser-known groups of sea reptiles. Together, plesiosauroids and pliosauroids make the Plesiosauria, a.k.a. "plesiosaurs" in broader sense, originating from the same common ancestor in the Triassic seas. The relationship of sauropterygians to modern reptiles has long been unclear. Once, they were placed with ichthyosaurs in their own subgroup (see further), and not related with any still-living reptilian group. Today, plesiosaurs ''sensu lato'' (pliosaurs included) are not thought to be closely related to ichthyosaurs. They seem loosely related to modern lizards, rather that to crocodiles and dinosaurs.

Like plesiosauroids, pliosauroids were widespread throughout the Mesozoic, 218-65 mya. Both subgroups shared the same body plan, with rigid bodies, short tails, and two pairs of powerful flippers — perhaps alternately-moved making a typical "double-wing" swimming effect (as seen in ''Series/WalkingWithDinosaurs''). The difference is in front of their shoulders. Pliosaurs had very short, stocky necks, and their heads were far bigger than that of ''Elasmosaurus''. Their teeth were less numerous, but much longer and stronger: like elasmosaurs, expect to see them visible when the mouth is closed, even though they may have been hidden by lips in RealLife. Despite the differences, the head anatomy of plesiosaurs and pliosaurs was the same. Both had eyes and nostrils placed above to see out of water when the rest of the head was submerged. Both shared a singular trait: each nostril had two chambers like fish, possibly giving them a directional sense of smell. We don’t know if they passed more time near the surface or in the deeps, but some think pliosaurs were more deep-creatures than plesiosaurs.

Pliosaurs were variably-sized, some were not bigger than dolphins, but the biggest ones are candidates for "the largest sea reptile" title — even though their size has often been exagerrated. Among the latter, ''[[ Liopleurodon]]'' and ''[[ Kronosaurus]]'' were among the top predators of the Jurassic and early Cretaceous oceans respectively. Once estimated at 16m long (10m is more likely), ''Kronosaurus'' is named for Cronus, a Greek Titan who [[ImAHumanitarian devoured his own offspring]] (Zeus and Poseidon among them). About the same length was the equally-coolly named ''Liopleurodon'', virtually identical to the former but with less teeth. As is usual with marine superpredators, both are usually depicted as [[CarnivoreConfusion merciless ever-hungry]] [[PrehistoricMonster killing machines]].

Despite this, pliosaurs have been the least-portrayed group of sea reptiles, and still remain mainly documentary animals. ''Kronosaurus'' was long the most commonly shown pliosaur in books and documentaries until 1999, when a memorable appearance of an [[RuleOfCool extraordinarily oversized]] [[note]]The fictional length 80ft/25m was based on misidentified bone fragments; in reality, the species maxed out at 25ft/7m long.[[/note]] ''Liopleurodon'' on Series/WalkingWithDinosaurs rapidly made it the new iconic member of the family (very similarly to ''Deinonychus'' à ''Velociraptor'' thanks to ''Film/JurassicPark''). In the show, an old male ''Liopleurodon'' was described weighing 150 tons (a bit less than the blue whale) and [[UpToEleven the biggest predator of all time]]. In particular, the scene in which he pulls the ichthyosaur in pieces [[NightmareFuel disturbed many viewers]] (even though the sad final scene where he’s stranded and slowly dies gives it a bit of humanity). To give the idea about how the animal remained impressed in pop consciousness: [[FollowTheLeader all successive depictions]] have shown ''Liopleurodon''s with the WWD blue-white color pattern. [[note]]For some reason, unlike dinosaurs and pterosaurs, marine reptiles are almost always shown with dull colors even in modern portraits. However, they might have been very colorful, like modern tropical seagoing animals.[[/note]] Another species that is starting to rise in popularity is ''Pliosaurus funkei'', known in popular culture as ''Predator X''. At an estimated 13 metres and 25 tons in weight (originally it was over 15 metres and 45 tons but ScienceMarchesOn), it's likely that it was the largest of this group and this was coupled with a bite that was estimated to be four times that of ''T. rex''. Is it any wonder this thing is becoming popular?

# '''Entry Time:''' 1999
# '''TropeMaker:''' ''Series/WalkingWithDinosaurs''

!! Fishes, dolphins, or lizards? [[ Ichthyosaurs]] *

Ichthyosaurs have the very evocative name of "fish-lizards": they really resembled large fish in shape and swimming style, but recall modern dolphins as well thanks to their flippers and their long "noses." Like fishes and unlike dolphins, they had ''four'' flippers (foreflippers were usually bigger) and an ''upright'' caudal fin. As a group, ichthyosaurs were the most ancient marine reptiles, and were widespread from the Middle Triassic until the Late Cretaceous, 245-90 mya, but went extinct 25 million years before the mass extinction. Once, ichthyosaurs, plesiosaurs and pliosaurs were put together in their own group, the "euryapsids," unified by having a single pair of fenestrae on the top of the skull. Today, "euryapsids" are firmly put in the diapsid group (which also included dinosaurs, pterosaurs and all living reptiles except maybe turtles). Ichthyosaurs were among the very first diapsids to have evolved: since they are not related with any modern animal group (thus preventing good comparisons), they still remain quite mysterious critters.

Descended from a still-unknown land-dwelling ancestor (remember ''every'' lineage of marine reptiles did descend from four-limbed terrestrial reptiles), ichthyosaurs were the most marine of all marine reptiles and never came onto land, not even to lay eggs. In fact, their young were born alive just like modern dolphins, as we can see in some fossils of mothers dead with their offspring ''just getting out of their body''. We now know that plesiosaurs also reproduced in the same way and probably never left the water either — however, the scene of a long-necked plesiosaur which crawls on the seashore like a sea lion is a [[ScienceMarchesOn staple in artwork]]. Ichthyosaurs are extremely abundant in fossil record: several individuals are preserved with soft tissue and, sometimes, ''even the print of the whole body''. Thanks to the latter, we know they had a dorsal fin and a crescent-shaped caudal fin as well as the four paired "flippers." A strange thing is, unlike modern sharks, the backbone curved ''downwards'' at the tail level, and filled the lower lobe of the caudal fin, not the upper one.

Their eyes were noticeably large for good vision; most portraits show ichthyosaurs with round pupils and no eyelids, like a typical fish. Skull nasal openings were just in front of the eyes, but the nostrils could have been on top of the head. Their skin was smooth and hydrodynamic like a dolphin, as shown in fossil prints. The mouth was usually filled with acute teeth: most ichthyosaurs ate fish, but ammonites and other shellfish were also on their menu. We don't know what amount of time they passed underwater: maybe they could extract some oxygen directly from the water like modern sea turtles, but they certainly did breath regularly like every reptile. The resemblance with dolphins means artists classically show ichthyosaurs jumping out of water in a dolphinish style, but this is not proven. Unusually for extinct reptiles, "fish-lizards" often escape the fate of being described as "monsters"... at least in modern documentaries. [[ScienceMarchesOn Originally]], ichthyosaurs were depicted as more crocodile- or mosasaur-like, with no caudal or dorsal fins. The famous "ichthyosaur" in Verne’s novel is based on this early interpretation. Several other fictional ichthyosaurs [[FollowTheLeader have then been inspired by the original]].

Today, more updated ichthyosaurs are regular sights in dino-books. They’re very useful to show evolutionary mechanisms, making a classic example of "convergent evolution" with fish and cetaceans. On the other hand, they are rarely seen in recent stories, much less than the long-necked plesiosaurs. Maybe they are not that exotic-looking, or just not impressive enough to attract writers’ interest. The species shown is always ''[[ Ichthyosaurus]]'', because was the first discovered [[OverlyLongGag in the 1810s in England, before the "first known dinosaurs]]," and the prototype of the group. Being only 8-10ft long in RealLife, expect to see it oversized and over-scary. And never mind that some other ichthyosaurs (''[[UsefulNotes/PrehistoricLife Temnodontosaurus, Cymbospondylus, Thalattoarchon, Shonisaurus]]''), being 25ft long or more and at least two of them being apex predators that killed huge prey, could be very apt for the role. The absence of ''Shonisaurus'' is particularly strange: as large as a sperm whale, it may be the biggest known sea reptile (and much bigger than the much-hyped [[Series/WalkingWithDinosaurs ''Liopleurodon'']].)

# '''Entry Time:''' 1852
# '''TropeMaker:''' Crystal Palace Park

!! Sea-serpents: [[ Mosasaurs]] *

The most recent group of Mesozoic sea reptiles, mosasaurs lived worldwide in the Late Cretaceous, at the end of the Age of Dinosaurs. They replaced ichthyosaurs and coexisted with the last plesiosaurs. While ichthyosaurs and plesiosaurs were not closely related with any modern reptile, mosasaurs are the only prehistoric animals which literally deserve the title of "giant lizards." They belong to the [[ squamates]], the group containing modern lizards and snakes [[note]]Never forget snakes ''are'' legless lizards just as birds are flying dinosaurs[[/note]], and were closely related to modern snakes and monitor lizards. Indeed, due to their elongated shape, they have often been compared with the legendary "sea serpent," and often depicted with a speculative dragon-like crest running along their back in much old art.

Descended from monitor-like animals, mosasaurs often reached gigantic sizes, but exaggerations tend to be common. Some source talk about 20m long animals, even though most giant mosasaurs were probably no more than 10m long. With their slender bodies, they were also less heavy than the robust plesiosaurs and pliosaurs. To be more hydrodynamic, they may have lost the original lizard scales and developed a smooth skin texture, like ichthyosaurs and plesiosaurs. Their tails were long and laterally-flattened: unlike plesiosaurs, they swam in a shark-like manner, swinging their tails side-to-side. Since many modern snakes and lizards are ovoviviparous (that is, produce eggs that hatch inside the mother’s body), this might also have been true for mosasaurs. In this case, they would have had no need to come ashore to reproduce, and could live entirely in water (now confirmed). Their limbs fin-like could be further proof. All marine reptiles described here obtained their flipper-like limbs in the same way of modern cetaceans, embedding their original digits in one single fleshy mass, and enormously multiplying the number of phalanxes (ichthyosaurs took this to an extreme).

Mosasaur heads were similar to those of modern lizards, but with longer snouts. Like the latter, they'd have had fleshy lips. Like modern snakes, their mouths had notably loose hinges between the jaws: this allowed mosasaurs to swallow big items without tearing them in pieces (which they could still do). The teeth were conical or specialized for crushing smaller species and serrated on the three largest species (the 40+-foot giants that are most often depicted), the upper ones placed in two rows on each half-jaw, again like modern snakes and monitors. According to stomach contents, mosasaurs were very generalist feeders: fish, sharks, squids, pterosaurs, early birds like ''[[UsefulNotes/PrehistoricLife Hesperornis]]'' and even smaller mosasaurs have been found. [[note]]This ''doesn’t necessarily mean'' they were cannibals, though: the preyed upon mosasaurs could be from different species than their predators. After all, modern orcas do eat smaller dolphins.[[/note]] We don’t known if mosasaurs had a forked tongue and ever-open eyes like many modern squamates, nor if they had heat-sensors like some boas and rattlesnakes: these things usually don't preserve in fossil record. However, it is interesting to know that a fairly close relative of both ''Mosasaurus'' and ''Tylosaurus'', ''Platecarpus'', is known to have a tail fluke on the dorsal and ventral sides of the tail, akin to sharks. It's thus possible that all mosasaurs shared this feature.

Like pliosaurs and ichthyosaurs, mosasaurs are a staple in documentaries, but are not-so-common in stories. Most "giant leviathans" with huge jaws seen in fiction tend to be generic monsters a la Verne, rather than precise kinds of sea reptiles. And don’t rule out seeing mosasaurs confused with [[ArtisticLicensePaleontology sharks]]. ''[[ Tylosaurus]]'' and the namesake ''[[ Mosasaurus]]'' are the stock members of the mosasaur family: needless to say, they're among the largest, up to 10-15m long. The former was found during the Bone Wars in the USA. The latter has a much more fascinating story. Found in the Netherlands near the Meuse river at the end of the 1700 (hence its name), ''Mosasaurus'' was not only the first sea reptile ever discovered, but the second fossil recognized by science as belonging to a Mesozoic reptile, after ''Pterodactylus''. See also UsefulNotes/PrehistoricLife.

In 2015, a (slightly oversized) ''Mosasaurus'' received top billing alongside a pack of trained ''Velociraptors'', the already-iconic ''TyrannosaurusRex'' [[MyFriendsAndZoidberg and]] Creator/ChrisPratt in the hit film ''Film/JurassicWorld''. The image of her leaping out of the water to be fed a shark was the second major marketing image used for the film (the first being Chris Pratt riding a motorcycle alongside the raptors), and it's been suspected that this film might help contribute to the species becoming more popular among a whole new generation of paleontology geeks. It was also regarded as the most accurate animal in the film despite being slightly oversized, which is quite an achievement in a film series that admits it's not scientifically accurate in the same film.

# '''Entry Time:''' 1852
# '''TropeMaker:''' Crystal Palace Park

!! A turtle outside a snake's body: ''[[ Archelon]]'' *

The only other marine reptile which has appeared in fiction more than once, ''Archelon'' lived in the same Late Cretaceous inland shallow sea which once covered the Great Plains. Discovered at the start of the 20th century, it shared its habitat with ''Elasmosaurus'', ''Tylosaurus'', and the flying ''Pteranodon'': its size and armor made adult ''Archelon'' virtually immune to predators. (Even though in [[Series/WalkingWithDinosaurs WWD]] a dead ''Archelon'' is shown killed by a giant mosasaur, but the latter was oversized.)

Not all Mesozoic reptiles were exotic critters, however. ''Archelon'' was just what it seems: a sea turtle. But it fits perfectly the subtrope "everything was huge in dinosaur times": it's among the largest known fossil turtles — 4m/13ft long and weighing several tons, ''Archelon'' was two to three times bigger than the biggest modern turtle (the [[ Leatherback turtle]], confirming TurtlePower is TruthInTelevision. However, it was not the ancestor of modern sea turtles: it belonged to a different lineage, the protostegids, which went extinct along the other giant reptiles at the end of the Cretaceous. Its name is a {{Portmanteau}} of ''arche'' (primeval) and ''chelon'' (turtle).

As turtles and tortoises have remained virtually unchanged since their first appearance in the Triassic, ''Archelon'' had the same traits seen in modern chelonians: beaked jaws, forelimbs transformed in strong flippers (with multiple phalanges as usual), weaker hind-flippers and short tail. However, its armor was lighter than most modern turtles, and the shell may have been leathery instead of horny. The modern turtle which mostly resembles an ''Archelon'' might just be the leatherback. As modern species of sea turtles eat very different items (some eat shellfishes, others seaweed, and some jellyfishes), we don’t know what were the ''Archelon''’s preferences. Almost certainly it came ashore to lay its eggs like its relatives.

Among the rare ''Archelon'' appearences in fiction, the most remembered is in Harryhausen's ''One Million Years B.C.''. The turtle is the first animal cavemen encounter in the island, [[UpToEleven upsized to be as big as a house]]. Surprisingly, many viewers think it was [[{{Slurpasaur}} live-acted by a Real Life turtle]], but it too is stop-motion like most other animals here. A Franchise/{{Pokemon}} based on ''Archelon'' made its debut in ''VideoGame/PokemonBlackAndWhite''; a two-stage fossil Pokémon, Tirtouga and Carracosta are interesting, as even fully grown they're actually ''smaller'' than their real world inspiration.

# '''Entry Time:''' 1966
# '''TropeMaker:''' ''Film/OneMillionYearsBC''

!! The Super Croc that's actually a Super Gator: ''[[ Deinosuchus]]''*

Okay, so it's not a ''sea'' reptile, but it's aquatic so it's just as good.

''Deinosuchus'' ("terrible crocodile", also called ''Phobosuchus'' "fearsome crocodile") belonged to the eusuchians, a.k.a. the "true crocodilians." This gigantic gator appeared only in the Cretaceous but had the same anatomy we still see today. More precisely, it was closer to alligators and caimans than to true crocodiles, hence the nickname "giant alligator". Like gators, the ''Deinosuchus''' skull had wide strong jaws and relatively blunt teeth. Its head was as long as a fully grown man, but the length of its body is unknown because the skull is the only surviving part. Comparing with modern alligators, ''Deinosuchus'' could have reached 15m in length and weighed more than a ''Tyrannosaurus''. Its home was freshwater basins in Late Cretaceous North America, but it could also have frequented the inland sea that divided the continent at the time. Since its fossil is from 75 mya, ''Deinosuchus'' could not have lived long enough to meet ''T. rex'' in RealLife, but only the latter's smaller relatives, like ''Albertosaurus''.

For [[RuleOfCool VERY obvious reasons]], ''Deinosuchus'' is a popular crocodilian choice in the world of DinosaurMedia, though curiously enough it's not quite as common in mainstream works as it is in educational ones. Naturally, its size and abilities will usually be exaggerated, though fortunately it tends to avoid foraging into PrehistoricMonster territory due to the fact that it was essentially a scaled-up alligator, and we have plenty of those in the modern day to use as points of reference[[note]]Interestingly, sufficiently giant alligators exist even today -- the largest on record was a whopping 15 feet in length and reportedly another one was caught that was around 19 feet in length -- though none of them make it to the same level of massiveness that ''Deinosuchus'' did[[/note]]. One noteworthy appearance was the fourth ''WesternAnimation/TheLandBeforeTime'' film, a cantankerous ''Deinosuchus'' appears as one of the two main villains (partnered with an equally disagreeable ''Ichthyornis''), while another was in an episode of ''Series/PrehistoricPark'', wherein Nigel brings one back to the present for his dinosaur zoo.

# '''Entry Time:''' 2006
# '''Trope Maker:''' Prehistoric Park

!!Other sea reptiles
Sorry, these aren't here. If you're looking for ''Stenopterygius'', ''Temnodontosaurus'', ''Mixosaurus'', polycotylids, thalattosuchians, nothosaurs, placodonts, and others, see [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles here.]]


!Mammal-like reptiles

At least pterosaurs and the above-mentioned seagoing animals are from the same Mesozoic time period. Don't even get us started on how [[ Synapsids]] (commonly named "mammal-like reptiles") are sometimes labeled dinosaurs.

[[folder:Synapsids in media]]

Most synapsids lived well before the appearance of the first dinosaur; indeed, synapsids were the very first large land vertebrates and diversified much during their time on Earth, until most of them got wiped out in the Permian mass extinction. In the Brave New World that followed, the few surviving non-mammalian species were outcompeted by [[ archosaurs]], the group containing dinosaurs, pterosaurs and crocodilians.

Synapsids had an extraordinary relevance in the history of evolution because they were the ancestors of mammals and thus of '''[[WhatMeasureIsANonHuman mankind ]]''' itself, and yet they have not gained popularity like that of the dinosaurs, probably because of their relatively small size compared to things like ''T. rex'' or sauropods.

''[[TaxonomicTermConfusion Technically]]'' they are not even "reptiles": they would better be called "mammal ancestors" or "proto-mammals".

!! Hairy lizard, or naked mammal? ''[[ Dimetrodon]]'' **

Lived in North America 280 million years ago, in the Permian period (just before the Triassic one). It is the only mammal-like "reptile" whose popularity matches that of the stock dinosaurs, thanks to its mohawk-esque crest (sail) on its back. Its iconic status among mammal-like reptiles is partially justified by its fossil abundance — dozens of specimens are known, juveniles included. As one could expect at this point, it was discovered [[OverlyLongGag in North America during the Bone Wars, in the second half of the 19th century]].

Being a very early mammal-ancestor, ''Dimetrodon'' still had a lizardy shape, with long tail, long body, splayed legs, and skull with a small braincase. Fossil prints show a lizard-like gait. Other traits, on the other hand, were quite mammalian: a laterally-flattened trunk (not wider-than-taller like most modern reptiles); a solid skull with one single pair of temporal openings placed near the maxillary hinge (the so-called "synapsid" condition also seen in mammals, us humans included); and differently-shaped teeth — ''Dimetrodon'' just means "teeth with two lengths." Even though all teeth were conical, the anterior ones were small and crammed together like incisors, while the longest teeth were in the place mammals have usually their canines. Behind them, the posterior teeth were small and not apt for chewing food unlike our molars, but are somewhat analogue to those seen in primitive insectivorous mammals. More evolved synapsids like ''[[Usefulnotes/PrehistoricLife Cynognathus]]'' achieved a clearly mammalian anatomy, with more erect limbs, shorter tails, larger brains, and teeth very similar to mammals.

Its "sail" sustained by elongated vertebral spines has always been a headache for scientists. The classic theory considers it a thermoregulating device. Turned to face the solar rays, it could have captured much heat like a solar panel; if turned parallel to them, it would have been more like a radiator, dispersing heat. Considering its desertic habitat, this hypothesis still remains a good one. Other theories are mating or threat display, inter-specific identification, and so on. Maybe the sail served for all these purposes. Among external features, ''Dimetrodon'' could also have had some sparse hair, hints of auricles and maybe even proto-milk glands. These things are totally uncertain, and given its primitiveness, are unlikely. The coloration is totally speculative — living in harsh habitat, it was likely brownish like modern desert mammals, but its sail could have been vividly coloured and/or able to change colors for display purpose. Sadly, synapsid soft tissues are virtually unknown. No eggs or nests are known from the dimetrodont, and we don’t know if it was oviparous, or viviparous like modern mammals (if the latter is true, viviparity was achieved independently).

''Dimetrodon'' is usually described as the top predator of its time, shown hunting early "amphibians" like ''[[UsefulNotes/PrehistoricLife Eryops, Diplocaulus, Seymouria]]'' etc., as well as what could be called its Non-Identical Twin, ''Edaphosaurus''. Its crest, its (apparently) [[ReptilesAreAbhorrent reptilian look]] and the meat-eating attitude makes the dimetrodon a predestined victim of DinosaursAreDragons and PrehistoricMonster both in fiction and in docu-media. However, if compared with other famous prehistoric animals, ''Dimetrodon'' could appear rather [[{{Narm}} narmy]] in comparison. If we imagine a battle against a ''Tyrannosaurus''/''Deinosuchus''/''Smilodon''/''Mosasaur'', the primitive and relatively small dimetrodont would always be the loser — this could also be true when put against modern predators (lions, Kodiak bears, Nile crocs etc), as well as most ancient and modern giant herbivores. But in Permian landscapes, ''Dimetrodon'' was still faster and more powerful than every other land animal, definitively debunking the {{Narm}} thing.

Although ''Dimetrodon'' is more closely related to ''you'' than to any dinosaur, and predated the first dinosaur by at least a country mile of geologic time, it is often mixed with dinosaurs in toy collections just because it [[RuleOfCool looks cool]]. In movies and comics, it may even show up living with cavemen. Expect to see it with a giant iguana-like look and ''scaly'' skin. Actually, scales are a strict reptilian thing, and ''Dimetrodon'' hide was probably naked like modern hairless mammals, with some [[ScienceMarchesOn hardened fish-like belly scales left over from its amphibian ancestry]]. Its shape makes the dimetro the most abused animal within the {{Slurpasaur}} trope. For example, in the 1970 film version of ''Literature/JourneyToTheCenterOfTheEarth'' some Caribbean iguanas with a ridiculous crest on their backs live-act ''Dimetrodon''s, which of course attack the humans.

# '''Entry Time:''' 1940
# '''TropeMaker:''' Disney/{{Fantasia}}

!! Other synapsids
Sorry, these aren't here. If you're looking for ''Ophiacodon'', ''Sphenacodon'', ''Cotylorhynchus'', ''Estemmenosuchus'', ''Anteosaurus'', ''Titanosuchus'', ''Dicynodon'', ''Thrinaxodon'', and others, see [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles here.]]


Even prehistoric ''mammals'' are sometimes mislabeled dinosaurs. Colloquially, this is often true of fish as well, or any prehistoric-looking creature, such as the [[UsefulNotes/PrehistoricLife Coelacanth]].

[[folder:Mammals in media]]

Among mammals, those living in the Ice Age are the most portrayed, because they lived along with [[AllCavemenWereNeanderthals the most iconic hominid species]].

!!One and the same? The [[ woolly mammoth]] and the [[ American mastodon]] ***

Mammoths and mastodons often show up in anything dealing with prehistory, though usually associated with the Ice Ages thankfully. The species definitely most portrayed of these is ''Mammuthus primigenius'', better-known as the woolly mammoth. Probably the most iconic non-dino prehistoric animal of all, thanks to the countless, extraordinarily well-preserved specimens with soft tissues, which make it perhaps the ''only'' prehistoric animal almost as scientifically well-known as a still-living animal.

A common misconception about the woolly mammoth is that it 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 [[UsefulNotes/PrehistoricLifeMammals Columbian mammoth]]. Also note that only males had the typical huge, curly tusks: the females' tusks were not that different from those of modern elephants. As preserved fossil hair is often reddish-brown, some depictions show woollies with this color: actually, this is due to a chemical change since 10,000 years ago. When alive they were blackish, as seen in the ''Series/WalkingWithBeasts''.

It's worth noting that mammoths, scientifically speaking, were just another type of elephant, since they belonged to the same phylogenetic branch. The Asian elephant is slightly more closely related to mammoths than to its more distant modern African relative (thus mammoths ''weren't'' the direct ancestors of elephants as sometimes said). On the other hand, the mastodon was ''not'' a true elephant, but just a distant relative of ''both'' modern pachyderms ''and'' mammoths — its scientific name, ''Mammut americanum'', is misleading. Like the true mammoths, the mastodon has left exquisite remains (ex. those in the Californian tarpits). Lived during the Ice Ages but in warmer climates than ''Mammuthus primigenius'', and was neighbour and possible prey for the "saber-toothed" ''Smilodon''. Interestingly, in some languages the adjective "mastodontic" has become a household word as a synonym of "huge," "enormous," but the animal wasn't actually that big compared with other extinct proboscideans (it was a bit smaller than a bush elephant). For other extinct elephant relatives, see [[UsefulNotes/PrehistoricLifeMammals Prehistoric Life]].

#'''Entry Time:''' N/A for the woolly mammoth which has been a cultural icon since prehistory. 1863 for the mastodon.
#'''TropeMaker:''' Literature/JourneyToTheCenterOfTheEarth (Mastodon)

!!Knife-teeth: ''[[ Smilodon]]'', aka the "saber-toothed tiger" ***

Saber-toothed cats, with their distinct fangs, are just as iconic in pop culture. There were many species of them, but the only saber-toothed cats you'll ever likely see are ''Smilodon fatalis'' and ''Smilodon populator'', which is larger but [[RuleOfCool has a less awesome name]].

Although "saber-tooths" belongs to the cat family Felidae, they are in a separate branch of that clade from modern felines; thus, the popular denomination "saber-toothed tiger" is not correct at all. The "tiger" thing means that ''Smilodon'' is often heard roaring just like an actual tiger or a lion, though only the big cats of the genus ''[[PantheraAwesome Panthera]]'' (that is, lions, tigers, jaguars and leopards) can roar thanks to the structure of their larynxes unique to this group. Even though scientists say the structure of the small bones in the saber-tooth's mouth are set up for making a sort of roar, this roar arguably was ''not'' identical to that of modern big cats.

It will probably use its sabers for every conceivable task, like slaying herbivores the size of mastodons or ''Megatherium'' with a single stab, despite the fact that most real saber-tooths (as well as their relatives, the [[UsefulNotes/PrehistoricLife scimitar-tooths]] and [[UsefulNotes/PrehistoricLife dirk-tooths]]) had relatively delicate fangs that could not safely be used for stabbing. Instead, it probably slashed out the throats of prey from below. Oh, and it'll be stripy, like a tiger, which — in ''S. populator'' 's case — isn't completely impossible, given that it lived on grasslands.

Expect to see ''Smilodon'' heavily interacting with humans, as our ancestors' main predator: in RealLife other carnivores such as [[UsefulNotes/PrehistoricLife prehistoric lions]] were probably more important predators. And expect to see it ''living alongside woolly mammoths''. Even though they were contemporary, their habitat in RealLife was largely different, with ''Smilodon''s preferring warmer climates[[note]]Though ''S. fatalis'' would have experienced snowy winters considering its region's climate at the time[[/note]]. And, naturally, don't exclude seeing saber-toothed cats somehow living alongside dinosaurs, and in the worst scenario, [[NinjaPirateZombieRobot fighting against a ''T. rex'']].

In RealLife, ''Smilodon'' was a bear-like specialized predator that was powerful but very slow-moving and mobile only in a straight line (in other words, a MightyGlacier). The teeth were used only for slashing the throat of prey that had already been subdued with its bodybuilder-like forearms. It is often portrayed living in wolf-like packs with both sexes actively hunting, though this is considered controversial by some scientists and there is not enough actual evidence to support it. It went extinct 10,000 years ago, after the Ice Age ended. Theories have been raised as to how they died off, such as through climate change thanks to the end of the Ice Age, the lack of big prey for it to hunt, or that humans changed their habitat by setting fires, killing off its food supply.

#'''Entry Time:''' 1903
#'''TropeMaker:''' The paintings of Charles R. Knight

!!Extinct rhinos: [[ Woolly rhinoceros]] and ''[[ Elasmotherium]]'' **

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.

''Elasmotherium'', also known as the unicorn rhino, is often confused with the woolly (''Coelodonta antiquitatis'') because of their similar appearance: however, the latter was no larger than modern white rhinos and had ''two'' horns as well; ''Elasmotherium'' was much larger (5 tons, like a modern bush elephant) and with one single horn... perhaps as long as a grown man, and located on the forehead rather than upon the nose: hence [[ExactlyWhatItSaysOnTheTin unicorn rhinoceros]].

Both lived in the Ice Age in cold climates, alongside mammoths in northern Asia, but the elasmothere had a more southerly range than the woolly rhino, and while both lived east of the Urals, only the woolly rhino was found in Europe[[note]]Possibly. There's [[ one cave painting]] that might stretch ''Elasmotherium'''s range as far as France[[/note]]; the latter lived alongside the other, more popular woolly ([[RhetoricalQuestionBlunder guess what]]).

Interestingly, both woollies have left soft parts of their bodies other than bones, hair included. The "unicorn rhinoceros" is often said to have been the inspiration of the {{Unicorn}} myths found all over Eurasia in one form or another when still alive, but this is probably a legend. Possibly. 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.

#'''Entry Time:''' 1918 (''Coelodonta''), 2006 (''Elasmotherium'')
#'''TropeMaker:''' Literature/TheLandThatTimeForgot (''Coelodonta''), Series/PrehistoricPark (''Elasmotherium'')

!!Big badass sloth: ''[[ Megatherium]]'' **

One of the largest land mammals that ever lived, ''Megatherium'' was the same size as an elephant or a ''T. rex'': it reached 5m when fully erect, and its name means... well... [[ExactlyWhatItSaysOnTheTin big beast]].

Lived just few thousands years ago in South America, and ancient humans knew it, to the point that they actually might have used it and other relatives as a... living pantry! Megathere's remains have been discovered in ancient caves, and it is thought that some human hunters enclosed some of these animals in those caves.

In old portraits, ''Megatherium'' was classically 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), while the three-clawed forefeet were used to pull down branches. Actually, our "big beast" was neither a horse nor a giraffe relative... 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, not to ungulates.

An extremely controversial idea is that ground sloths might have supplemented their diet with meat that they scavenged from predators such as saber-tooths by chasing them away from their kill. There isn't much to support this theory other than RuleOfCool, though.[[note]]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.[[/note]] This did not stop ''Series/WalkingWithBeasts'' from depicting ''Megatherium'' chasing some ''Smilodon'' 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''. Some portrayals take this depiction UpToEleven by having it be an ''active hunter'', knocking over animals like glyptodonts to tear open their soft belly.

''Megatherium'' is the most well-known species, due to being the largest. It's commonly depicted alongside the aforementioned mammoths, despite being strictly South American. ''Megalonyx'' was the sloth species that was common in North America, but it was about half the size of its more famous cousin.

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. In prehistoric terms, though, he seems to be closest to the [[ Nothrotheriops]] at least in terms of appearance. The most bizarre portrayal would have to be in the 1948 B-movie ''Film/UnknownIsland'', where a ground sloth was depicted as a strange, roaring predator that resembles a cross between a gorilla and a bear.

#'''Entry time:''' 1864
#'''TropeMaker:''' Literature/JourneyToTheCenterOfTheEarth

!!Ancient bears: [[ Cave bear]] and [[ short-faced bear]] **

The most famous extinct bear is the cave bear (''Ursus spelaeus''), whose remains are extremely abundant in European caves. Quite similar to a modern Kodiak in shape and size, but with a bigger hump on its shoulder and a more prominent skull, the cave bear is often portrayed as [[BearsAreBadNews the archenemy of Neanderthals]], because both lived in the same places (Pleistocene Europe) and were forced to share the same caves to repair themselves from the frigid Ice Age winters. But it's more probable that Neanderthals (and humans) were actually the worst enemies of cave bears, and some think they could even have contributed to cave 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 be what contributed to its extinction.

The North American short-faced bear (''Arctodus''), in contrast to its stockier cousin, had long limbs, a [[ExactlyWhatItSaysOnTheTin bulldog-like snout]], and 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 is 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. However, 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.

Expect the two to be confused in pop culture, despite being quite different in appearance, and the short-faced bear being more related to the South American spectacled bear than the modern grizzly. 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, its South American relative ''Arctotherium'' is actually larger.

#'''Entry Time:''' 1897
#'''TropeMaker:''' A Story of the Stone Age

!!Big Badass Wolf: [[ Dire wolf]] **

The dire wolf (''Canis dirus'') was a wolf bigger than ours, possibly a hunter of giant bison in competition with saber-tooths. 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 ''Rancho la Brea'', in Los Angeles.

In real life, the dire wolf wasn't much larger than the modern grey wolf, and probably not too different in appearance. However, it had a much more powerful bite, well over twice that of its relative. 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).

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.

!!UpToEleven trophy: ''[[ Megaloceros]]'' **

Now we enter the world of the most successful ungulates today, Artiodactyls (even-toed ungulates), and how could make this without starting with the most spectacular extinct deer (and one of the most astonishing mammals ever)? But wait: even though it is commonly referred to as the Irish elk, ''Megaloceros'' (more precisely ''Megaloceros giganteus'', also called "Megaceros" in older sources) was more closely related to the European fallow deer. Maybe it was not the largest deer ever (being moose-sized), but its antlers were another matter: they could make the modern moose's antlers appear insignificant in comparison. Each one was ''as long as the entire animal's body'', and each weighed more than 100kg. Obviously, only males had such a thing, as with most modern deer. Some scientists believe that ''just this headgear'' was the cause of its extinction, having grown too much, and making the animal too clumsy... but this is unlikely; if they actually were too big, evolution would have simply made them smaller at some point. ''Megaloceros'' lived in Europe in the Ice Ages alongside woolly mammoths and other large mammals, and was possibly prey for ancient humans; its nickname "Irish elk" is due to its remains being very common in {{Oireland}}. ''Eucladoceros'' ("well-ramified horn") and ''Cervalces'' ("moose-deer") were other spectacularly big-antlered extinct cervids, but other prehistoric deer had normal-sized prominences on their heads.

!!Bigfoot?: ''[[ Gigantopithecus]]'' **

''Gigantopithecus'' was a relative of the orangutan that also exhibited gorilla-like characteristics. Found in Southern Asia from China to India, its name means "giant ape," and with good reason. It measured up to 10 feet when standing upright, ''two times'' bigger than a modern silverback gorilla: a sort of middle-way between a RealLife gorilla and Film/KingKong.

Sadly, the only certain thing we know about it is just a fossil lower jaw; the shape of the teeth show us it was a plant-eater, possibly specialized to a bamboo-based diet, to the point that some experts think competition with ''the giant panda'' actually drove it to extinction.

At least part of the reason the ape has entered stock territory is due to some scientists speculating that it might have been the inspiration for the mythical yeti (especially since it was discovered in the Himalayas). Some cryptozoologists have taken these theories UpToEleven, speculating that not only did it survive to modern times, but at least one lineage migrated to North America and evolved into Bigfoot. Thanks to this radical theory, ''Gigantopithecus'' has been mentioned in virtually every Bigfoot documentary.

There are quite a few problems with this theory. First of all, there is absolutely zero fossil evidence that it survived that long, much less that it made it to North America. It's quite unlikely that such a large creature could go unnoticed for so long without leaving ''some'' sort of proof of its existence. Secondly, since the creature was specialized for eating mostly bamboo, it's doubtful it would survive in a temperate environment without its preferred diet, much less spread throughout North America.

Despite this, the "Gigantopithecus = Bigfoot" theory is so persuasive that the ape is often depicted in models and illustrations in an upright stance like a man, just to fit into this theory. Since all we have are its jaw and teeth, its hard to be sure, but judging by its relationship with other apes, it most likely walked on its knuckles like they did. Since primates standing upright requires 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.

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 [[Disney/TheJungleBook the 1967 Disney classic]], King Louie was [[AdaptationSpeciesChange changed]] from an orangutan to a ''Gigantopithecus'' to avert MisplacedWildlife. 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 animated counterpart, chasing Mowgli through the ancient temple ruins in a memorably chilling sequence. Both film appearances [[ShownTheirWork correctly]] depict ''Gigantopithecus'' as orangutan-like apes, walking quadrupedally on its knuckles as opposed to upright like a human.

!!Big badass armadillos: ''[[ Glyptodon]]'' and ''[[ Doedicurus]]'' *

After ankylosaurs went extinct, evolution decided to create their mammalian equivalents: the glyptodonts. They were xenarthrans as well, but related to armadillos rather than to sloths.

Lived in South America for a dozen million years, before going extinct only a few thousand years ago: in short, they had the same history as their cousins, the giant sloths. Both groups were herbivores (though giant sloths might have been at least partially scavengers), and when adult, they feared no predators except humans. There is a secret behind giant sloths' and glyptodonts' success: their backbone. It was far, far stronger than that of any other mammal, permitting them to carry such heavy bodies around without suffering back pain.

''Glyptodon'' is the most well-known glyptodont, but it's also worth mentioning ''Doedicurus'': with its mace-like tail, it was the most ankylosaur-like of them all. These were among the biggest glyptodonts, and thus [[RuleOfCool the most depicted]].

Speaking of glyptodonts' armor, it 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 whose armor was more flexible and spiky. With their compact frame and rigid armor, Glyptodonts were probably slower-moving than ankylosaurs, 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 their tail was also covered by bone.

Like ''Megatherium'', ''Glyptodon'' was known to ancient humans; we now know human hunting wiped out these species, as the species on islands were the last to go, and as there is evidence of human hunting and change in their habitat. Now, only far smaller xenarthrans survive; armadillos, tree sloths and true anteaters (sadly, the natural history of anteaters is poorly-understood).

!!South American tapir-camel: ''[[ Macrauchenia]]'' *

This bizarre creature resembles a llama or humpless camel in appearance (its name even means “long llama”), but actually belongs 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, or odd-toed ungulates.)

One of its most distinct features is its nostrils, which are placed on its ''forehead''. This results in it always being depicted with a flexible tapir-like proboscis. However, if you compare a [[ tapir skull]] to that of [[ Macrauchenia]], you can see that the tapir has a bony projection on its forehead to hold the skull in place, which ''Macrauchenia'' lacks. Therefore, it's more likely the animal had a bulbous trunk similar to that of a Saiga antelope.

Another distinct feature is its leg bones, which are not only built for extremely fast speeds, but also some of the sharpest turns of any herbivorous mammal. This makes sense when you realize it evolved alongside the infamous [[UsefulNotes/StockDinosaursTrueDinosaurs terror birds]], which were not only fast runners but, like most birds, had really good color vision, meaning camouflage wasn't an option.

Other predators of it included carnivorous sprassodonts like ''[[UsefulNotes/PrehistoricLifeMammals Thylacosmilus]]'', and, after the Great American Interchange, North American invaders like cougars, jaguars, the giant bear ''Arctotherium'', and, most famously, ''Smilodon''.

It 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}}''. If it ever appears in non-documentary fiction, don't expect it to be referred to by name.

!!A run toward the future: [[ Horse ancestors]] *

Horses. The eternal symbol of evolution. Almost as much as the dodo is the icon of extinction. And yet, horse ancestors weren't so cool-looking compared to most other extinct [[ hoofed mammals]], really. The most famous of these is, obviously, the [[RuleOfCool least horse-like]] of them all: ''Eohippus'' --> ''Hyracotherium'' --> ''Eohippus'' --> ''Protorohippus''. An almost-unbelievable ScienceMarchesOn affair has encircled horse's evolution, despite its iconic role in popular science. Anyway, all this doesn't involve us so much. Expect to see this (whatever name is to be used) small, basal ungulate called ''horse'' anyway, despite it actually having nothing more in common with horses than with tapirs or rhinos: the "Hyracotheohippus stew" includes several different early ungulates, some of theme ''were'' horse ancestors and some weren't. Systematics of primitive ungulates (called "condylarths") is a total mess. Among confirmed horse ancestors, they make a sort of {{pun}} if read together: ''Mesohippus'', ''Merychippus'', ''Pliohippus'' and dozens of other ''-hippus''... all North American. Also worth of note is ''Hipparion'' which, sadly, breaks the theme of having ''-hippus'' as suffix; it also breaks the geographic rule, being an Old World critter, an offshoot of the horse tree which didn't leave any descendants. Remember that ''all'' modern equines descended from North American ancestors. And oh: the latter were not only the horse's ancestors, but also the donkey's and zebra's, never forget this. Modern equids are so closely related to each other, they could well be considered variations of a single kind of animal; indeed, they are all put in a single genus, ''Equus''.

Whenever ''Hyracotherium'' or ''Eohippus'' shows up in media, expect them to be portrayed as a RedShirt often falling prey to the giant flightless bird ''Gastornis''. Now that [[ScienceMarchesOn science has marched on]], it is highly unlikely for the birds to have any interests in the small ungulates due to their herbivorous diet.

!!Saber-toothed rhino: ''[[ Uintatherium]]'' *

As we'll say later, not all rhinoceros-looking fossil mammals were real rhinos, although they'll probably get identified as such in popular media. Among the most well-known is ''Uintatherium'', found in huge numbers in several fossil deposits in the western USA and in China. The uintathere is perhaps [[TheWoobie the most mistreated]] extinct mammal of them all: expect somebody describing its appearance as "[[PrehistoricMonster monstrous/scary]]." Right, it had six giraffe-like horns and two upper protruding tusks, but, honestly, if ''Uintatherium'' was alive today, it would probably appear no more scary than an elephant, rhino, hippo or giraffe. Also expect a crack about its "tiny" brain (just like what happens to its [[TheWoobie Woobiesaurian]] equivalent, ''[[StockDinosaurs Stegosaurus]]''), and just like the stegosaur, expect the writer to cit [[TooDumbToLive its dumbness as the real reason for its extinction]]. 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[[note]]In [[ the Eocene epoch]], to be precise[[/note]], before being outcompeted by the even larger brontotheres (see below) and the first true rhinos.

!!Thunder beasts: ''[[ Megacerops]]'' and '' [[ Embolotherium]]'' *

''Megacerops'' (formerly called ''Brontotherium''... these ''[[UsefulNotes/StockDinosaursTrueDinosaurs Bronto]]''s just can't keep their names) the prototype and the most well-known member of its group of mammals, the [[ExactlyWhatItSaysOnTheTin brontotheres]]. [[note]]However, one brontothere, the primitive ''Brontops'', preserved its bronto- prefix... until it was reclassified as a synonym for ''Megacerops''[[/note]] While ''Uintatherium'' was not related with any modern hoofed mammals, brontotheres were distant relatives of [[ horses, tapirs and rhinos]]. The biggest brontotheres were almost Triceratops-sized or elephant-sized, and their cool name indeed means "thunder beasts." They had a more rhino-like look than uintatheres, having one single "horn" on their nose: ''Megacerops'' 's prominence was forked and slingshot-like, while that of ''Embolotherium'' (the brontothere portrayed in ''Series/WalkingWithBeasts'') was shovel-like and not forked. Like uintatheres, brontotheres too roamed plains of the northern continents in huge numbers in the Early Cenozoic; they eventually went extinct, perhaps because they weren't able to adapt to the diffusion of the very first grasslands which replaced their former foods (scrub and non-grass herbs).

!!Brontomammal has many names: ''[[ Paracera-Indrico-Baluchi-therium]]'' *

Here is Our Majesty, the biggest land mammal that ever lived — though some [[ScienceMarchesOn recent research]] seems to indicate that some mammoths and the giant straight-tusked elephant ''Palaeoloxodon namadicus'' were heavier, but both were certainly not as tall. Despite its really gigantic size — it was as tall as an ''Apatosaurus'' up to the shoulders, and weighed as much as ''three'' elephants or, better, three ''T. rex''es — it still had a quite slender, elegant frame: a sort of muscular giraffe with a long neck, small hornless head, and long, slender limbs. Its behavior itself was probably more giraffe-like than rhinoceros-like, browsing the tree tops. In short, it was the new mammalian brachiosaur. Lived at the middle of the Cenozoic (the Age of Mammals), 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 — for example the prototype of the group, ''Hyracodon''. Our record-holder is also a prime example of IHaveManyNames among prehistoric critters: now called ''Paraceratherium'', its traditional names are ''Indricotherium'' and ''Baluchitherium''.

!!Forks, shovels, and spears: [[ Gomphotheres]] and ''[[ Deinotherium]]'' *

There were A LOT of other extinct elephant relatives in prehistory: not so in {{Prehistoria}}. Don't expect to see any proboscideans in TV outside docus unless it's a woolly mammoth or an [[StockDinosaurs American mastodon]], even though many of them were far cooler-looking than the latter two. If you don't believe us, take a look at the following examples.

''Gomphotherium'' 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. Smaller than modern elephants, they were once classified within the "mastodons," but the latter has revealed to be an artificial assemblage of archaic proboscideans, only united by one thing: they had a pair of tusks ''both'' in their upper jaw ''and'' in the lower one. In ''Gomphotherium'', ''Platybelodon'', and other "gomphotheres," the upper ones were small and normal-looking; the lower tusks were placed on the tip of the jaw, were flat and very untusk-like, maybe used to "gather" ground-level vegetation like a literal shovel. One gomphothere, ''Amebelodon'', had expecially long "shovels" on a relatively short mandible; others, like ''Stegotetrabelodon'', had more pointy lower tusks. Gomphotheres are often shown with bizarre ''flat'' trunks, but this is actually unproven — trunks have not bones within, so they didn't fossilize. However, recent studies suggest gomphotheres had 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, the aforementioned Mûmakil were shown in TheFilmOfTheBook with a pair of gomphothere-like lower tusks.

Other "mastodons" were more similar to elephants, but even they would appear cool-looking by our standards: see ''Anancus'', the "European mastodon," with its straight, spear-like upper tusks (while the lower ones were almost missing). Even closer to the proper elephants (forming the sister clade outside the elephant-mammoth group) were the stegodonts. Among them, ''Stegodon ganesa'' had huge parallel tusks so close to each other that illustrations show the animal as obligated to keep its trunk ''aside'' the two tusks!

A more primitive proboscidean lineage includes the huge ''Deinotherium'' ("terrible beast"). Unlike the former, it had only two tusks like modern pachyderms... only, they ''grew out of the lower jaw''. Curved downwards, the function of these tusks is still uncertain (maybe to strip the bark from trees). Some deinotheres were as big as the aforementioned giant mammoths, but others were no bigger than a modern Asian elephant. Deinotheres lived in the Cenozoic era, and some managed to survive long enough to meet our first human ancestors in Africa.

!!Other prehistoric mammals
Sorry, these aren't here. If you're looking for ''Mammuthus columbi'', ''Mammuthus trogontherii'', dwarf elephants, ''Titanohyrax'', ''Machairodus'', ''Homotherium'', ''Megantereon'', ''Dinofelis'', ''Miacis'', ''Bison priscus'', ''Bison antiquus'', ''Andrewsarchus'', ''Livyatan'', ''Mylodon'', ''Castoroides'', Ceratogaulids, ''Phoberomys'', ''Palaeochiropteryx'', ''Planetetherium'', ''Diprotodon'', ''Thylacosmilus'', ''Thylacoleo'', and others, see [[UsefulNotes/PrehistoricLifeMammals here.]]


!Prehistoric Fish

It's not often that you'll see prehistoric fish in paleo-media, but when you do, it will usually be these guys.

[[folder:Fish in Media]]

!!''Jaws'' on steroids: The [[ Megalodon]] shark ***

It's usually accepted that the biggest/most spectacular prehistoric animals lived in the Dinosaur Age: well, sharks are 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 even 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 is ''Carcharodon megalodon'' or ''Carcharocles megalodon''. [[note]] If it was an extremely close relative of the great white shark (''Carcharodon carcharias''), the correct name is ''Carcharodon''; if not, it's ''Carcharocles''. [[/note]]. Like the most impressive extinct beasts, the Megalodon is often victim of sensationalism. Some sources describe it as 30m long, like a blue whale; actually it was only slightly over half this length. Still, it remains the biggest known fish and largest and most successful (with a tenure of 20 million years, when most last just one) apex predator ever.

It may have been a specialist whale hunter, and its bite marks have been found in whale skeletons, but it could also have fed on smaller prey, too. We don't know why it went extinct; maybe because of climatic changes that deprived it of its main food source, in particular the closing of the Central American Seaway, which was an important hunting and migration area. One final note about Megalodon: it was so successful it held back the evolution of whales, which underwent a third explosion in diversity right after its extinction (therefore, the theory orcas outcompeted the shark is highly unlikely).

Megalodon is probably the one prehistoric creature that gets almost as much sensationalism as ''TyrannosaurusRex'' itself. From frequent, fraudulent reports of it still patrolling the seas or erroneous portrayals of it chomping on marine reptiles (despite not appearing until ''after'' those creatures had already gone extinct), ''Megalodon'' is frequently cast as the ultimate sea predator, despite basically just being a scaled-up great white.

# '''Entry Time:''' Late 2000s
# '''Trope Maker:''' Itself

!!Killer Fish: ''[[ Dunkleosteus]]'' (once called ''Dinichthys'') *

Most placoderms were small. But ''Dunkleosteus'' is a ''real'' exception. 19ft long, the size of a great white shark, it was only outmatched by its larger but gentler cousin ''Titanichthys'' and an obscure chimera known as ''Parahelicoprion'' for the title of largest animal in the Paleozoic. It was the same shape as the smaller and lesser known ''Coccosteus'', with the same kind of armored head and the same strange scissor-like teeth (well, actually, they're plates of sharpened bone). It was evidently the top predator of its time (the Devonian), able to chop up even the toughest prey. Studies of its jaw reveal that it probably sucked up food like a vacuum, using its bone plates to slice prey into chunks with a bite force of ''4400 pounds''. Its fossilized vomit has been found too, indicating that they often regurgitated the armour and bones of their prey. Also of interest is that several ''Dunkleosteus'' fossils preserve evidence of being attacked by another ''Dunkleosteus'', which has led some to suggest they were active cannibals. In older sources it is referred to as ''Dinichthys'' ("terrible fish"; may or may not be a separate animal though); the much less awesome name ''Dunkleosteus'' means "Dunkle's bone" after a museum curator.

Despite its impressiveness, ''Dunkleosteus'' has not gained much attention outside paleo books; in ''Series/ChasedByDinosaurs'' it appears as one of the "[[PrehistoricMonster monsters]]" encountered by Nigel Marven during his time travel, and to fit better the role is portrayed [[RuleOfScary overscary]], with cat eyes and blood-red coloration.

# '''Entry Time:''' 1956
# '''Trope Maker:''' Documentary and book media

!!Other prehistoric fish

Sorry, these aren't here. If you're looking for ''Coelacanthus'', ''Leedsichthys'', ''Hybodus'', ''Tullimonstrum'', and others, see [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures here]].


!Prehistoric Invertebrates

[[folder:Invertebrates in Media]]

!!The first eyes: [[ Trilobites]] ***

Some things are more important than others. Trilobites are among them. Their [[http:/ extreme abundance]] in the fossil record had made them index fossils: that is, Paleozoic terrains can be easily recognized ''just because'' they almost certainly contain at least one trilobite. As a group, trilobites lived through the whole Paleozoic era, but became rarer and rarer after the Devonian, and none survived the Permian-Triassic mass extinction. Though their appearance could lead to them being confused with crustaceans, they were actually not related to any modern arthropod; they are classified in the middle between the two main arthropod groups: chelicerates (arachnids + sea spiders + horseshoe crabs) and mandibulates (hexapods + myriapods + crustaceans).

"Trilobite" means "three lobes." Their body was divided in three parts: the head, the segmented thorax, and the telson (the scute at the rear end of the body). But their flattened body also shows three parts in the longitudinal sense, the middle one and the two lateral. Like a millipede they had many pairs of legs (up to 100), one pair of antennae, and two usually large eyes similar to those of insects: trilobites were among the first creatures capable of seeing images. They mainly lived in the benthic zone; some were diggers, other active swimmers; some were able to curl themselves for protection. Most were not bigger than a human hand; the biggest were 3ft long. Like the contemporary jawless fishes, trilobites only ate small items, and were prey for other arthropods, cephalopods, or jawed fish. We don't know if trilobites were totally aquatic or came to land to lay their eggs. Their young were identical to the adults. The kinds of trilobites commonly shown in media pertain usually to the Phacopida subgroup; good luck if you see an agnostid or a proetid trilobite.

In fiction, trilobites can often be seen in underwater visuals (even in the Mesozoic, despite this being millions of years after their extinction) as ambient animals that skitter about on the ocean floor. They're much more common in older works, and tend to solely exist as a "Look, something that looks primitive! We're in prehistory alright!" type of thing.

# '''Entry Time:''' Unknown
# '''Trope Maker:''' Educational media.

!!Ammon's horns: [[ Ammonites]] ***

Is there anyone who hasn't seen those spiral stony shells emerging from the surrounding rocks? Ammonites (technically the ammonoids) have always been among the most iconic fossil invertebrates, together with the trilobites. Like the latter, they have been used as index fossils, but for the Mesozoic era. Actually, some ammonites lived in the Paleozoic, but they reached their prime in the Dinosaur Age. They went definitively extinct at the end of the Mesozoic, when the comet struck. [[note]] Even though it resembles an ammonite, the extant nautilus is not an ammonite descendant. [[/note]] Despite the abundance of their shells, their soft bodies are rarely preserved and little-known. Like octopuses and squid, they had certainly tentacles and the beak typical of cephalopods, but the number of tentacles is uncertain. They may have had more than eight to ten tentacles, more like a nautilus than a squid. It's unsure if their tentacles had suckers like octopuses and squid, or lacked them like a nautilus.

And we don't know if they sprayed ink, nor if they had complex eyes to see images like octopuses and squid.

With their heavy shells, ammonites were probably slow swimmers; they were surely predators like every other cephalopod, but they probably caught only small prey. Their hard shells were an excellent protection against predators, as shown by some ammonites with marks of teeth left by an ichthyosaur or a mosasaur which tried to break the shell in vain. Though most ammonites were no bigger than a human hand, some reached a diameter of 3m (smaller than a giant squid in length, but heavier in weight). In media, ammonites are always shown with the classic curly, laterally-flattened shell; however, the shells of some Cretaceous ammonites showed unusual forms. Some had [[ loosely uncoiled shells]], some had [[ u-shaped shells]], some had [[ spiny tower-like shells]], some just had [[ straight shells]], other had [[ shapes so bizarre]], no one is sure how they survived.

Ammonites, like trilobites, are common as ambient animals in paleo-media, though their presence in Mesozoic works at least makes more sense seeing as they were ''extremely'' common back then and their fossils are among the most common ones discovered. So common in fact, individual ammonite species are used as "index fossils", with their presence in layers of rock denoting specific geological time zones.

# '''Entry Time:''' Unknown
# '''Trope Maker:''' Educational media.

!!First Flyer: ''[[ Meganeura]]'' **

''Meganeura'' was a griffinfly (basically a giant dragonfly relative); with a wingspan like a crow, it is the biggest known TRUE insect of all times (millipedes are NOT insects!), and a very powerful flyer like modern dragonflies. Unlike ''Arthropleura'', ''Meganeura'' was carnivorous and fed on smaller insects and maybe even small amphibians. Both animals were usually safe from the super predators of the time: the millipede's armor and the griffinfly's agility protected them against giant amphibians and fish.

In media, ''Meganeura'' is more common than its land-bound neighbor, but not quite common enough to be counted as "Great Stock." Unlike ''Arthropleura'', ''Meganeura'' tends to be an ambient animal that exists mostly to show something prehistoric and (given its size) possibly ramp up the {{Squick}} factor. Frustratingly, older works tended to portray ''Meganeura'' living alongside dinosaurs, despite the fact that it had already died out long before the dinosaurs arrived on the scene. A particularly confusing appearance of a ''Meganeura'' was in the novel version of ''Jurassic Park'', where a cloned one was present in the park despite having gone extinct long before any mosquitoes or even amber would have existed.

# '''Entry Time:''' 1885
# '''Trope Maker:''' Educational media.

!!Monster Millipede: ''[[ Arthropleura]]'' *

Why did land arthropods reach such a large size in the Carboniferous? [[note]]But don't forget most Carboniferous land arthropods were normal-sized; [[BiggerIsBetter obviously]], those don't gain much attention in media.[[/note]] Probably because the oxygen content at the time was much greater than every other period. The tracheal respiratory system of insects and land arthropods prevents them from reaching a big size: over a certain size, this system just doesn't work. The maximum an insect can reach depends also on the quantity of oxygen in the atmosphere; thus, more oxygen —> bigger size. The myriapod ''Arthropleura'' was the UpToEleven case: as long as a human, it is the the biggest known land arthropod of all time. But it was an inoffensive herbivore that fed on the rotting vegetation extremely abundant in the Carboniferous forests. In truth, this "giant millipede" didn't even resemble a millipede. Wide and flattened, it resembled more a overly long trilobite. Actually there are modern millipedes that have the same body shape of ''Arthropleura'', though obviously much smaller.

Despite this critter's bizarre and frightening appearance, it has very little presence in the media. However, it has become noteworthy enough that it's now a common sight in paleo-books and documentaries talking about life ''before'' the dinosaurs. The most noteworthy appearance of an ''Arthropleura'' in a non-educational work was ''Series/{{Primeval}}'', which for some reason decided to portray it as a giant venomous centipede.

# '''Entry Time:''' 2005
# '''Trope Maker:''' ''Series/WalkingWithMonsters''

!!Other prehistoric invertebrates
Sorry, these aren't here. If you're looking for prehistoric crustaceans, ''Palaeophonus'', belemnites, rudists, graptolites, and others, see [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures here]].

!! Other extinct creatures
Sorry, these aren't here. If you're looking for crocodylomorphs, ''Protosuchus'', ''Hallopus'', ''Pristichampsus'', mekosuchines, ''Bavarisaurus'', ''Varanus priscus'', ''Postosuchus'', ''Rutiodon'', ''Euparkeria'', ''Erythrosuchus'', ''Kuehneosaurus'', ''Sharovipteryx'', ''Longisquama'', ''Scutosaurus'', ''Procolophon'', ''Eudibamus'', ''Triadobatrachus'', ''Karaurus'', ''Eocaecilia'', ''Eryops'', ''Cacops'', ''Platyhystrix'', ''Cothurnocystis'', and others, see [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles here]] or [[UsefulNotes/PrehistoricLifeOtherExtinctCreatures here]].