History UsefulNotes / StockDinosaursNonDinosaurs

These reptiles were only unified by the fact that were aquatic but less specialized than the classic marine reptiles within the main folder above. They were also usually smaller-sized than them.

''Nothosaurus'' ("false lizard") looked a bit like ''Tanystropheus'', but its neck wasn't as excessively long, and it was actually related to the ancestors of plesiosaurs. Like the long-necked plesiosaurians, ''Nothosaurus'' had needle-like teeth set in elongated but weak jaws; unlike plesiosaurs, it had a well-developed tail for swimming by undulating like a mosasaur, and short, splayed true legs with palmated feet. Because of the latter feature, it and the other nothosaurs have often been portrayed as sort of like seals or sea otters of the Triassic, coming onto land to lay their eggs but feeding with agility in the water on fish and shellfish. ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Askeptosaurus]]'' was apparently similar to a nothosaur, but belonged to a more archaic group: The Thalattosaurs (lit. "sea lizards", even though the askeptosaur is believed a freshwater-dweller), once put together with the champsosaurs in the artificial assemblage of the Eosuchians (meaning "dawn crocs").

''Placodus'', the prototype of the eponymous Placodonts, was similar in overall shape to ''Nothosaurus'' but more massively-built and much shorter-necked, with powerful short jaws and flat crushing teeth for eating shellfish. Apart from this, its lifestyle was probably analogous to ''Nothosaurus'', and like the latter it swam using its tail. ''Placodus'' ("plate-tooth") had also light armor consisting of a line of bony plates running along its whole backbone, but the most derived placodonts like ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Henodus]]'' developed literal shells and were very turtle-like (a classic case of convergent evolution).

''[[http://en.wikipedia.org/wiki/Mixosaurus Mixosaurus]]'' has traditionally been the most familiar primitive ichthyosaur, also from the Triassic. It had already the classic head, neck and body of the more known/derived ''Ichthyosaurus'', but its tail fin was still small, because the vertebrae of its tail don't show the downward bend of the derived ichthyosaurs, and we don't know if it had a dorsal fin or not. Smaller than ''Ichthyosaurus'' (some individuals were only 1m long), ''Mixosaurus'' might recall an ichthyosaur with a mosasaurian tail, or even a tiny mosasaur that looked like a dolphin.

''Champsosaurus'' lived as late as the Cretaceous; it belonged to a particular lineage of archaic reptiles, the Neochoristodera (once put in the Eosuchians as said above), which arose in the Triassic and managed to survive beyond the great dinosaur extinction, just like turtles, crocs, tuataras, lizards, and snakes. But unlike all them, they went extinct not long after the start of the Mammal Age, long before humans appeared. ''Champsosaurus'' was like an undersized, 1.5m-long crocodile in shape (its name means "croc-lizard"), and sometimes is wrongly portrayed in documentary media as a true crocodilian living alongside others like the "supergator" ''Deinosuchus''.

''True'' crocodile-relatives, on the other hand, were the Jurassic ''Metriorhynchus'', ''Geosaurus'', and ''Teleosaurus'', which are here for comparison, but should more correctly be put together with ''Deinosuchus'' and ''Sarcosuchus''. However, unlike the mostly freshwater modern alligators and kin, they adapted to a fully marine lifestyle. ''[[http://en.wikipedia.org/wiki/Metriorhynchus Metriorhynchus]]'' ("moderated snout" because of its thin jaws) and the very similar ''[[http://en.wikipedia.org/wiki/Geosaurus Geosaurus]]'' were both Late Jurassic: they lose their armor altogether, developed a caudal fin very similar to an ichthyosaur or a mosasaur, and their limbs became similar to paddles, though still not proper flippers like those of a plesiosaur, ichthyosaur, mosasaur, or sea turtle. When they and their relatives (the aptly-named sea crocodiles, ex. ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Dakosaurus]]'') appear in docu-media, they're portrayed as underdog predators of their time with respect to giant plesiosaurs (''Liopleurodon'') and in competition with primitive sharks like ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Hybodus]]'', ichthyosaurs like ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Ophthalmosaurus]]'', or small long-necked plesiosaurs like ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Cryptoclidus]]''.

''[[http://en.wikipedia.org/wiki/Teleosaurus Teleosaurus]]'' was a more archaic Jurassic sea-crocodile, resembling a small gharial in shape: it still had a light dorsal armor, weak but still land-adapted legs, and normal tail. Some sculptures of it are portrayed in the Crystal Palace Park of London together with other more famous Mesozoic reptiles -- unusually, still accurate today.

These guys were among the oddest and most specialized reptiles ever, despite their smaller size compared to many other reptiles of the Mesozoic. They were primitive archosaur-relatives like ''Euparkeria'', but unlike the latter they have never been considered "thecodonts", not even in the past. Both lived across the Triassic.

''Tanystropheus'' was 4-5m long and notable for its enormously long neck compared with its shorter body and tail, to the point that it could be mistaken for a plesiosaur at a glance. Its neck was proportionally even longer than a classic plesiosaur or a typical sauropod, and was made by few extremely long vertebrae that made it stiff. Once, the neck and the rest of the body were believed from two distinct animals! But the tanystropheus had true, if short, legs, not flippers like the plesiosaurs, making it looking like a lizard with a giraffy neck. It was probably amphibious and a hunter of small aquatic prey, but its hunting style is unknown. Once considered a plesiosaur ancestor, ''Tanystropheus'' actually belonged to its own group of archosaur-relatives. In ''Series/SeaMonsters'' it is shown losing its tail like many modern lizards do, after Nigel Marven tempted to stop it by grabbing the tail. This is actually an [[RuleOfCool invention of the show]], because ''Tanystropheus'' was not a true lizard (unlike the mosasaurs, which also did not lose their tails like modern monitors); furthermore, it's unlikely that such a damaged animal of its size would still be able to swim correctly by using its tail as a propeller as shown in the program.

''Hyperodapedon'' was very different: it was an herbivorous land reptile of the successful group of archosauromorphs named the Rhynchosaurs. The latter could be mistaken for true archosaurs of the Triassic like the "thecodonts" or even for contemporaneous mammal ancestors like the Dicynodonts. Curiously, the rhynchosaurians were [[ScienceMarchesOn once considered]] relatives of the modern tuatara despite the two animals' different appearance. ''Hyperodapedon'' (more traditionally called ''Scaphonyx'') is portrayed in paleo-art because of its strange owl-like "face": it had an uncinated beak with a split in its upper half which the lower half fitted into when the mouth was closed, and eyes pointing forwards just like an owl. This reptile and its closest relatives have usually been described as sluggish critters unable to flee to the faster predators of the time like the rauisuchians and the first meat-eating dinosaurs, but this might not be true: the rhynchosaurs' short splayed limbs and bulky body don't mean they were slow and harmless, and ''Scaphonyx'''s parrot-like bill was powerful enough to deliver nasty bites to its attackers, like the beak of a modern macaw parrot or snapping turtle.

''Kuehneosaurus latus'' from Triassic Europe, and ''Coelurosauravus'' from Permian were much smaller than the two reptiles above, just a few feet long, but both deserve the popular nickname of "gliding lizards" — the first one was even a close relative of Lepidosaurs (snakes, lizards and tuataras), the second a basal diapsid. Both animals had protruding ribs, but not because they were especially skinny: these rib protrusions pointed sideways from the body and were connected by skin like the famous ''Dimetrodon'' sail, forming wings for gliding from one tree to another. Today, a modern true lizard convergently evolved a similar gliding mechanism, the so-called "flying dragon" of southeastern Asia (''[[http://en.wikipedia.org/wiki/Draco_volans Draco volans]]''). ''Icarosaurus'' ("Icarus lizard") was related with and similar to ''Kuehneosaurus'', but lived in Triassic North America. ''Coelurosauravus'' (whose odd name means "[[UsefulNotes/StockDinosaursSaurischianDinosaurs coelurosaur ancestor]]") was portrayed in the series ''Primeval'' as a human's pet. ''Weigeltisaurus'' was very similar to ''Coelurosauravus'', to the point once the two were considered one and the same.

Triassic ''Longisquama'' means "long scale": today regarded as an archosaur-relative, its classification has long been a headache for paleontologists. Also a few feet long like ''Kuehneosaurus'' but found in the former USSR in TheSeventies, it has usually been considered a gliding creature like the latter, using the eponymous "long scales" to cross the air like a modern flying squirrel, but this is not certain. As its huge protrusions resembled feathers a bit, it was even believed to be an ancestor of ''birds'' in the past — and anyway, the ScienceMarchesOn story of this enigmatic critter has been extremely convoluted. Another "gliding lizard", the only one known with bat-like skin-membranes, was ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Sharovipteryx mirabilis]]'' ("admirable Sharov's wing") of Triassic Asia; this one was hypothesized in the past to have been the ancestor of pterosaurs, but astonishingly, was related with the much bigger aquatic ''Tanystropheus''. ''Longisquama insignis'' (its full name, meaning "notably long scale") appears in ''WesternAnimation/{{Dinosaur}}'' as a sorta flying chameleon using its scale-things as the feathers of [[ArtisticLicensePalaeontology actual wings]].

#'''TropeMaker:''' ''Series/{{Primeval}}'' (Coelurosauravus), ''WesternAnimation/{{Dinosaur}}'' (Longisquama)

"Thecodont" ("teeth in sockets") is a now-abandoned term at least in cladistics for basal archosaurs or their close relatives that were neither dinosaurs, nor pterosaurs, nor crocodilians. They were all from the Triassic, and were the real dominant reptiles of this geological period, to the point that dinosaurs are often quoted as their natural successors in the following Jurassic and Cretaceous periods. However, at least initially they were in competition with Triassic mammal-ancestors and proto-mammals. Many "thecodonts" went extinct at the mass-extinction at the end of the Triassic: the latest ones lived alongside the first dinosaurs like ''Coelophysis'' and ''Plateosaurus'', but others went extinct earlier. [[ScienceMarchesOn Research since the 2000s]] indicates that some "thecodonts" weren't true archosaurs.

The most striking ones were perhaps the [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles giant Rauisuchians]] of the Late Triassic, because they were theropod-like predators in competition with the first carnivorous dinosaurs. ''Series/WalkingWithDinosaurs'' popularized one of them, the North American ''[[http://en.wikipedia.org/wiki/Postosuchus Postosuchus]]'' ("Posto's lizard"), found in 1985 in Texas. There were also the herbivorous, heavily-armored Aetosaurs (''[[http://en.wikipedia.org/wiki/Desmatosuchus Desmatosuchus]]'' being the most famous), and the aquatic and very croc-like Phytosaurs (''[[http://en.wikipedia.org/wiki/Rutiodon Rutiodon]]'' being the most-often portrayed), both groups also often of large size and living throughout the Triassic period. Proterosuchians like ''[[http://en.wikipedia.org/wiki/Erythrosuchus Erythrosuchus]]'' and the namesake ''[[http://en.wikipedia.org/wiki/Proterosuchus Proterosuchus]]'' roamed only the start of the Triassic, but were also as large as many modern crocodilians. All them can wrongly be presented as true crocodiles in media. Aetosaurs were a bit like ankylosaurs, Rauisuchians were more like theropods, Phytosaurs had unusual nostrils in front of their eyes, Eryrthosuchids had huge heads and forward-pointing eyes, and Proterosuchids had uncinated upper jaws like some dinosaurs like ''Dilophosaurus'' or spinosaurids.

Perhaps the most common thecodont in popular dinosaur books and documentaries has been ''[[http://en.wikipedia.org/wiki/Euparkeria Euparkeria]]'', often wrongly cited as an ancestor of the dinosaurs because of its partially-bipedal shape. Just 3ft long, this small archosauriform lived in the Early Triassic in the same epoch as many therapsids (''Cynognathus'', ''Lystrosaurus'', ''Thrinaxodon'', etc.), giant amphibians (''Mastodonsaurus'' etc.), and other much larger quasi-archosaurs (''Erythrosuchus'', ''Proterosuchus'', etc.). Some of these animals (''Cynognathus'', giant amphibians, and its fellow archosauriforms) were all potential predators of ''Euparkeria''. ''Euparkeria capensis'' means "Parker's good (animal) of the Cape" because was found in South Africa, at the start of the 20th century.

The even smaller ''[[http://en.wikipedia.org/wiki/Lagosuchus Lagosuchus]]'' (''Lagosuchus talampayensis''), only one foot long, and thus called "rabbit-croc", was an actual ancestor of dinosaurs, but lived in Middle Triassic Argentina. Some sources have wrongly classified it as "the first dinosaur" (see also ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Eoraptor]]''). It may have had some feather-like or hair-like structures in its body, like the related pterosaurs and dinosaurs.

Before the discovery of ''Lagosuchus'' in the 1970s, other "thecodonts" were considered the direct ancestors of dinosaurs, especially the European ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Saltoposuchus]]'' ("hopping-footed croc") and to a lesser degree ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Scleromochlus]]''[[note]]The latter could be an ancestor of pterosaurs, though.[[/note]] — and some were often even considered early proper dinosaurs (more precisely early theropods), notably the 12 ft long ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Ornithosuchus]]'' ("bird-croc"), the 2 ft long ''[[UsefulNotes/PrehistoricLifeOtherSmallTheropods Saltopus]]'' ("hopping foot"), and the large, 20 ft long ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Teratosaurus]]''. Actually, ''Ornithosuchus'', ''Teratosaurus'' and ''Saltoposuchus'' [[note]]but not ''Saltopus'', a close dino-relative like ''Lagosuchus''[[/note]] were more closely related to crocodilians than to dinosaurs or pterosaurs; the same is true of the Rauisuchians and Aetosaurs above. Phytosaurs, on the other hand, were long believed to be direct crocodile ancestors, but according to [[ScienceMarchesOn recent research]] they are not even archosaurs sensu stricto, just like ''Euparkeria''.

''Archelon ischyros'' lived in the Late Cretaceous inland shallow sea which once covered the Great Plains of the U.S. 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 — though in [[Series/WalkingWithDinosaurs WWD]] an ''Archelon'' is shown killed by a giant mosasaur, but the latter was oversized.

Not all Mesozoic reptiles were exotic by modern standards. ''Archelon'' was simple a sea turtle. But it perfectly fits the subtrope that 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 [[http://en.wikipedia.org/wiki/Dermochelys_coriacea Leatherback turtle]]). 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 into strong flippers (with multiple phalanges, as usual for sea reptiles), weaker hind-flippers and a 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 ''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 ''Archelon''’s preferences were. Almost certainly it came ashore to lay its eggs like its relatives.

Among ''Archelon''’s appearances 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, 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. An ''Archelon'' named [[ALizardNamedLiz Archie]] also appears in ''The Land Before Time'' film series, in the usual role of the old wise counselor typical for fictional talking turtles. 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.

''Deinosuchus'' ("[[NeverSmileAtACrocodile terrible crocodile]]", also called ''Phobosuchus'' "[[NeverSmileAtACrocodile fearsome crocodile]]"), belonged to the eusuchians, a.k.a. the true crocodilians. This gigantic alligator (thus more correctly called "Super Gator" than "Super Croc") appeared only in the Cretaceous but had the same anatomy we see today. More precisely, it was closer to alligators and caimans than to true crocodiles and gharials. Like gators and caimans, ''Deinosuchus''' skull had wide strong jaws and relatively blunt teeth, contrasting with the narrower jaws and more acute teeth of true crocs and gharials. Its head was as long as a full-grown man, but the length of its body is unknown because little more than the skull has thus far been found. By comparison with modern American alligators, ''Deinosuchus'' may 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 fossils date to more than 70 mya, ''Deinosuchus'' probably didn't live long enough to meet ''T. rex'' in RealLife, but only the latter's smaller relatives, like ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Albertosaurus]]''. It is usually shown in docu-media ambushing giant dinosaurs like a Nile Croc does with zebras, especially hadrosaurs like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Parasaurolophus]]'' or ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Corythosaurus]]'', but its actual lifestyle is unknown -- maybe it fed mainly on large fish or other water creatures such as small freshwater plesiosaurs/mosasaurs, turtles, smaller crocs, or champsosaurs (see "Primitive Reptiles"). Its reproductive methods are also unknown, but probably it built nests on riverbanks for its eggs like modern crocodilians.

''Sarcosuchus imperator'' ("Emperor meat-eating croc") lived earlier than ''Deinosuchus'', in the Early Cretaceous. It was found originally in Brazil and named "''Crocodylus'' (a modern crocodile genus)" ''hartii'' in 1869, but it was only recognized as a new genus from remains found a century later in Niger, together with some dinosaurs like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Ouranosaurus]]'' that could have been its prey. It was still too primitive to be an Eusuchian, but resembled one in shape: with its long thin jaws, it recalled closely the modern [[http://en.wikipedia.org/wiki/Gavialis_gangeticus gharial]] of India. It was about the same size of ''Deinosuchus'' but slenderer; some remains from South America are also known possibly belonging to it or to a close relative. Like ''Deinosuchus'', its lifestyle is only a guess.

For [[RuleOfCool obvious reasons]], ''Deinosuchus'' and ''Sarcosuchus'' are popular crocodilian choices in the world of DinosaurMedia, though they're not quite as common in mainstream works as they are in educational ones. Naturally, their size and abilities will usually be exaggerated, though curiously they tend to avoid foraging into PrehistoricMonster territory due to the fact that they were essentially scaled-up alligators/gharials, and we have plenty of them in the modern day to use as points of reference[[note]]Interestingly, sufficiently giant american 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 — though none of them are as massive as ''Deinosuchus''.
Also some indian gharials are said to reach similar sizes of the former gators, but never the level of ''Sarcosuchus''.[[/note]]. One noteworthy appearance of ''Deinosuchus'' was the fourth ''WesternAnimation/TheLandBeforeTime'' film, in which a cantankerous ''Deinosuchus'' appears as one of the two main villains (partnered with an equally disagreeable proto-bird, ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Ichthyornis]]''), while another was the protagonist of the last episode of the 2006 ''Series/PrehistoricPark'', wherein Nigel brings one back to the present for his dinosaur zoo - and is considered by him the hardest animal to catch of the whole series, even more than the ''Tyrannosaurus rex'' of the first episode. ''Sarcosuchus'' appeared in the 2003 miniseries ''Series/ChasedByDinosaurs'', with a rather minor role in the story -- basically the only purpose of the programmers was to add another giant reptile along with the others met by Nigel in his TimeTravel. Both ''Deinosuchus'' and ''Sarcosuchus'' reappear in 2011 in the BBC's "heir" of WWD, ''Series/PlanetDinosaur'', both with minor roles - useless to say, dinosaurs are the main characters as usual.

!! Titan Snake and Mega Lizard: ''[[http://en.wikipedia.org/wiki/Titanoboa Titanoboa]]'' & ''[[http://en.wikipedia.org/wiki/Megalania Megalania]]'' *

It's not common to see snakes in prehistory media, even documentaries; however, in recent years ''Titanoboa cerrejonensis'' ("Cerrejon's [[ExactlyWhatItSaysOnTheTin titanic boa]]") has been gaining in popularity.

This huge snake was found only in 2009, and lived in what is today Colombia (South America) just few million years after the extinction of the dinosaurs. It was one of the top predators in this Paleocenic world (unlike the famous bird ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Gastornis]]'', which recent research indicates was a herbivore). Although it was ''not'' as big as sometimes reported ("only" one or two meters longer than the biggest green anacondas or reticulated pythons), ''Titanoboa'' was more heavily-built, and may have weighed an impressive 1 ton; green anacondas reach 200 kg at the most, reticulated pythons slightly less so. Despite the early period at which it lived, ''Titanoboa'' was closely related to modern constrictors (the Boidae family), more to true boas and anacondas than to true pythons, and like all them it arguably preserved vestigial hindlimbs in the form of small "spurs". It was not venomous, and probably gave birth to live offspring like the closer boas/anacondas (pythons lay eggs and take care of them by coiling around them).

The Komodo dragon-like ''Megalania prisca'' (Megalania = "big tearer") has been known far longer; it was described by Richard Owen (the dinosaurs' TropeNamer) in the 19th century. It was an extinct goanna (the name for Australian monitor lizards), and was extremely closely related to modern ones, to the point that it's often put today in the same genus, ''Varanus'' (and thus renamed ''Varanus priscus''). It was about twice the length of the largest living monitor, the Komodo dragon, and was one of the top predators of Ice Age Australia, in competition with the marsupial lion and some land-dwelling crocodilians (the [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Mekosuchines]]). Whatever the name, this giant monitor is the largest-known fully terrestrial lizard of all time. Its behavior was arguably similar to that of modern goannas, and like them almost surely had a snake-like forked tongue to detect odors from the soil, likely laid eggs (oviparous) like all modern monitors, and likely was an intelligent animal with complex behavior like them. We don't know, however, if it was venomous like the Komodo dragon, but if it was it would have been the largest venomous animal ever. ''Megalania'' went extinct only a few thousand years ago, along with many Australian megafauna, at about the same time as the extinction of the woolly mammoths; it may have been killed at least indirectly by the fires created by the first prehistoric human colonizers of the LandDownUnder.

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

Among the rarely-seen marine reptiles in Fictionland, the giant ichthyosaur ''Shonisaurus'' deserves special mention because it's been frequently depicted in popular dinosaur books since its relatively recent discovery.

In a sense, ''Shonisaurus'' ("Shoshone lizard") could be considered the ichthyosaurian equivalent of the giant pterosaur ''Quetzalcoatlus''. Both were discovered in TheSeventies in the central USA, but their geological epochs were ''widely'' different: ''Quetzalcoatlus'' lived at the end of the Dinosaur Age, ''Shonisaurus'' at the start of it, in the Late Triassic. The wingspan of ''Quetzalcoatlus'' was also about the same as the total length of ''Shonisaurus'', 12-15m.

''Shonisaurus popularis'' was commonly accepted to have been the biggest ichthyosaur ever, and also the largest animal of the Triassic period — as long as the longest "[[UsefulNotes/PrehistoricLifeSauropodPredecessors prosauropods]]" (sauropod predecessors like ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Plateosaurus]]'') but heavier, 20-30 tons, comparable to a humpback whale or a medium-sized sauropod; but the recently- discovered ''Shastasaurus sikanniensis'' (a species of the traditionally smaller Triassic ichthyosaur ''Shastasaurus'') has revealed to have been even bigger, 20-22m long, and the biggest sea-reptile known to science. ''Shastasaurus sikanniensis'' was originally considered a species of ''Shonisaurus'', and some still argue that it should be considered so; if true, ''Shonisaurus'' would detain the record of "the Largest Ichthyosaur".[[note]]Though this could be blown out of the water if and when a more complete specimen of the 2018 "Lilstock ichthyosaur" is found; the current fragmentary remains were estimated via comparison to ''Shastasaurus'' to possibly result in a length of 26m and a weight near 100 tons, which if correct puts it within the size range of blue whales (''Balaenoptera musculus''), and thus the second largest animal to ever live.[[/note]]

''Shonisaurus'' and its relatives together comprise the Shastasaurians (once named Shastasaurids), an early lineage of true basal ichthyosaurians that went extinct in the mass extinction at the end of the Triassic, along with several non-dinosauria reptiles (the "thecodonts" or basal archosaurs, the rhynchosaurs, etc.), and most mammal ancestors. Shastasaurians had a typical ichthyosaurian fishy or dolphinish shape, but with a more primitive tail rather similar to that of the mosasaurs, longer hind-flippers than most ichthyosaurs, and fewer or none teeth in their mouths. ''Shonisaurus popularis'' had small teeth only in the front mouth, ''Shastasaurus sikanniensis'' totally lacked them. Their lifestyle is uncertain: they could be like sperm-whales in respect to dolphins or orcas, swimming slower than other ichthyosaurs and eating fish or cephalopods of small/medium size, but not hunting giant marine preys the size or bigger than them like orcas do. Some even suspect they could have also been partially filter-feeders, like modern baleen-whales.

''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 word "pterosaur" was coined; this explains why 'pterodactyl' has become the stock name of pterosaurs.

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 during the Late Cretaceous in the inland Western Interior Seaway of North America, ''Elasmosaurus'' was discovered in the USA shortly before the famous 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/PrehistoricLifeNonDinosaurianReptiles), and this explains why the animal in the oldest paleo-art [[https://youtu.be/pQJIVxzIUic has a short neck and an extremely long tail]]. The prototypical ''Plesiosaurus'' was the first described plesiosaur (1821), before even the earliest-discovered dinosaurs, ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Megalosaurus]]'' and ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Iguanodon]]''. First found in Dorset, England by Mary Anning, it was much smaller (16ft long), lived earlier (at beginning of the Jurassic) and was proportionally shorter-necked and longer-headed than ''Elasmosaurus'' -- though popular portrayals sometimes show it as a miniature elasmosaur, with a longer neck and smaller head than in RealLife.

The long-necked plesiosauroids belong to the Sauropterygia supergroup, which also includes the [[http://en.wikipedia.org/wiki/Pliosaur Pliosaurs]] (or pliosauroids, so-called from their traditionally obscure namesake, ''[[http://en.wikipedia.org/wiki/Pliosaurus Pliosaurus]]''; see below) and other lesser-known groups of sea reptiles, like [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles the nothosaurs and placodonts]]. Together, plesiosauroids and pliosauroids make the group 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 the ichthyosaurs in their own subgroup Enaliosauria, and were not believed to be related to any still-living reptilian group. Today, plesiosaurs ''sensu lato'' (pliosaurs included) are not thought to be closely related to ichthyosaurs. Instead, they seem distantly related to modern turtles (which actually doesn't help matters that much since turtles themselves are of equally unclear relationship to the other modern reptile lineages).

[[http://en.wikipedia.org/wiki/Ichthyosaur 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 snouts. 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 KT extinction for unclear reasons. 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). Ichthyosaurs were among the very first diapsids to have evolved: since they are not related to 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 descended 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 — even though 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 imprint 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 the backbone curved ''downwards'' at the tail level, and filled the lower lobe of the caudal fin, not the upper one — the exact opposite of modern sharks.

Their eyes were notably large for good vision; most portrayals 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 might have been on top of the head like modern whales (though this is totally speculative). Their skin was smooth and hydrodynamic like a dolphin, as shown in fossil prints: they were perhaps the ''only'' reptiles ever whose skin was totally scaleless, convergently with cetaceans. 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 percent of time they passed underwater; they may have been able to extract some oxygen directly from the water like modern sea turtles, but they certainly did breathe regularly like every reptile.

The resemblance to dolphins has classically led artists to 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 portrayed 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 a regular sight in dino-books. They’re very useful for showing evolutionary mechanisms, providing a classic example of convergent evolution with fish and cetaceans. On the other hand, they're rarely seen in recent stories, much less than the long-necked plesiosaurs. Maybe they're 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. While it was only 8-10ft long in RealLife, expect to see it oversized and overly scary. If shown to proper scale, expect to see its resemblance to dolphins played up heavily; it's likely that its dolphin-like appearance is precisely why ''Ichthyosaurus'' maintained "stock" status instead of being displaced by bigger but less dolphinish ichthyosaurs. Some of them (''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Temnodontosaurus, Cymbospondylus, Thalattoarchon, Shastasaurus, Himalayasaurus]]'', and the most famous, ''Shonisaurus''), were 25ft long or more, and at least two of them were apex predators that killed huge prey. The absence of the Shastasaurian ichthyosaurs (see below) is particularly strange: with some as large as a giant sperm whale, they may be the biggest known sea reptiles, and much bigger than the much-hyped [[Series/WalkingWithDinosaurs ''Liopleurodon'']].

The most recent group of Mesozoic sea reptiles, [[http://en.wikipedia.org/wiki/Mosasaur mosasaurs]], more properly the Mosasaurids, lived worldwide in the Late Cretaceous, at the end of the Age of Dinosaurs. They replaced ichthyosaurs in their ecological niche and coexisted with the last plesiosaurs. While ichthyosaurs and plesiosaurs were not closely related to any modern reptile, mosasaurs are the only prehistoric animals which literally deserve the title of "giant lizards". They belong to the [[http://en.wikipedia.org/wiki/Squamata Squamates]] (lit. "the scaly ones"), the clade 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 [[https://youtu.be/pQJIVxzIUic a speculative dragon-like crest running along their back]] in much old art.

Descended from monitor-like lizards[[note]]the scientific consensus has gone back and forth on whether monitor lizards or snakes are the closest living relative of the mosasaurs, but either way snakes are themselves currently believed to descend from monitor-like lizards[[/note]], mosasaurs often reached gigantic sizes, but exaggerations tend to be common. Some sources speak of 20m long animals, 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 but unlike plesiosaurs), but some skin prints seemingly show they preserved scales on their bodies. Their tails were long and laterally-flattened: like sharks and ichthyosaurs and unlike plesiosaurs, they swam by swinging their tails side-to-side. It's been confirmed that at least some were ovoviviparous (that is, producing eggs that hatch inside the mother’s body). Thus, they would have had no need to come ashore to reproduce, and could live entirely in water. Their limbs fin-like may be further proof. All marine reptiles described here obtained their flipper-like limbs in the same way as modern cetaceans, embedding their original digits in one single fleshy mass, and enormously multiplying the number of phalanges (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 large prey without tearing them into 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/StockDinosaursSaurischianDinosaurs Hesperornis]]'' and even smaller mosasaurs have been found.[[note]]This ''doesn’t necessarily mean'' they were cannibals, though: the preyed-upon mosasaurs might've been from different species than their predators. After all, modern orcas eat smaller dolphins.[[/note]] We don’t know if mosasaurs had a forked tongue and eyes that didn't close, like many modern squamates, nor if they had heat-sensors like some boas and rattlesnakes; these things usually don't preserve in fossils. However, it is interesting to know that a fairly close relative of both ''Mosasaurus'' and ''Tylosaurus'', ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles 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. Older depictions of mosasaurs usually gave them a rather crocodilian profile, with sword-shaped tails, but recent reevaluations of body shape together with the discovery of the ''Platecarpus'' tail fluke have led to newer reconstructions being more massive in the upper torso and neck, somewhat whale-like or ichthyosaurian in appearance.

Like pliosaurs and ichthyosaurs, mosasaurs are a staple in documentaries, but are not so common in fiction. Most giant leviathans with huge jaws seen in fiction tend to be generic monsters a la Verne, rather than exact species of sea reptiles. And don’t rule out seeing mosasaurs confused with [[ArtisticLicensePaleontology sharks]].

''Tylosaurus'' and the clade's 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 U.S.A. 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 prehistoric sea reptile ever discovered, but the second fossil recognized by science as belonging to a Mesozoic reptile, after ''Pterodactylus''. See also UsefulNotes/PrehistoricLifeNonDinosaurianReptiles.

In 2015, a (slightly oversized) ''Mosasaurus'' received top billing alongside a pack of trained ''Velociraptors'', the already-iconic ''Tyrannosaurus rex'' [[MyFriendsAndZoidberg and]] Creator/ChrisPratt in the hit film ''Film/JurassicWorld''. The image of her leaping out of the water to be fed [[TheWorfEffect 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 acknowledges its own lack of scientific accuracy.

''Pteranodon'' lived 86-84 million years ago on the shorelines of the inland sea that covers what is today Kansas, Nebraska, and other midwestern U.S. states. It had the typical traits of the most evolved pterosaurs, the pterodactyloids (aka literal pterodactyls). It had an elongated head, weak hindlimbs, only a hint of a tail, and very long wings with a huge "wing-finger," while the other digits were very small and may have been almost useless. It was one of the most specialized flying animals that ever lived, but very clumsy on land, where it walked slowly on all fours. With a wingspan of 6 m/20 ft, it was once considered the largest animal to ever fly, and the absolute limit for flying animal size.

This has been considered the ultimate GiantFlyer among prehistoric animals. Living in North America at the very end of the Cretaceous, 68-66 mya (but some think its distribution was worldwide), ''Quetzalcoatlus northropi'' 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 has 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 "[[FeatheredDragons feathered snake]]" -- the animal itself is often called "the quetzalcoatl". Its name also recalls that of the modern [[http://en.wikipedia.org/wiki/Quetzal Quetzal]], the long-tailed bird sacred to the Aztecs. In 2021, a second smaller-sized (6 m/20 ft wingspan) ''Quetzalcoatlus'' species, ''Quetzalcoatlus lawsoni'', was described.

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

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'', which shows up occasionally). As with most prehistoric animals, only the largest will be mentioned from each group, 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 it, too, was a very small member of its 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 to enter into 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: more like MixAndMatchCritter-type [[SeaMonster sea monsters]] than their RealLife counterparts. The "ichthyosaur" is similar to a mix-up of whales, crocodiles, dragons and snakes, and doesn't have the familiar fish-like shape of a real ''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 see in the individual sections below.

Another long-standing cliché makes sea reptiles the pterosaurs' archenemies. You've probably 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[[note]]Creator/DougalDixon once speculated that long-necked plesiosaurs would be specialist seabird/pterosaur hunters if they survived to the present[[/note]]. A good example of this is in Disney's ''Fantasia'', but the cliché itself is much older-- [[https://en.wikipedia.org/wiki/Duria_Antiquior an 1830 painting]] depicts a plesiosaur reaching its neck out of the water to seize a pterosaur. In RealLife this would be possible only for the biggest mosasaurs and pliosaurs, and even then, we don't have any evidence that either of these preyed on pterosaurs; in fact, we have more evidence that large fish, predatory dinosaurs, and marine crocodiles would have fancied a leathery-winged snack. 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''. Fossils of a juvenile ''Pteranodon'' have been discovered in the belly of a plesiosaur fossil, but given what is known about plesiosaur ecology, they were probably scavenged.

[[http://en.wikipedia.org/wiki/Plesiosaur Plesiosaurs]] (more correctly, plesiosauroids) are among 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 appearance 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 sticking outside their mouth, often oversized and more protruding than in RealLife, resembling the fangs of boa or python snakes.

These animals are traditionally described as slow 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, 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. There is also evidence of plesiosaurs having a fluke on their tail that acted as a rudder.

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 America, ''Elasmosaurus'' was discovered in the U.S.A. shortly before the famous 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/PrehistoricLifeNonDinosaurianReptiles), and this explains why the animal in the oldest paleo-art [[https://youtu.be/pQJIVxzIUic has a short neck and an extremely long tail]]. The prototypical ''Plesiosaurus'' was the first described plesiosaur (1810s), before even the earliest-discovered dinosaurs, ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Megalosaurus]]'' and ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Iguanodon]]''. First found in England, it was much smaller (16ft long), lived earlier (at beginning of the Jurassic) and was proportionally shorter-necked and longer-headed than ''Elasmosaurus'' — though popular portrayals sometimes show it as a miniature elasmosaur, with a longer neck and smaller head than in RealLife.

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 overturn your tiny boat or raft). Needless to say, almost every time a plesiosaur shows up, ''someone'' will bring up the [[StockNessMonster Loch Ness Monster]].

The long-necked plesiosauroids belong to the Sauropterygia supergroup, which also includes the [[http://en.wikipedia.org/wiki/Pliosaur Pliosaurs]] (or pliosauroids, so-called from their traditionally obscure namesake, ''[[http://en.wikipedia.org/wiki/Pliosaurus 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, 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 distantly related to modern lizards or maybe turtles, rather than 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 moved alternately to produce 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 an ''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 in proportion, 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-sea creatures than plesiosaurs.

Pliosaurs were variably-sized, some were no bigger than dolphins, but the biggest ones are candidates for the title of largest sea reptile ever — though their size has often been exaggerated. Among the latter, ''Liopleurodon'' and ''Kronosaurus'' were some of the top predators of the late Jurassic and early Cretaceous oceans respectively. First-found in Australia in 1924 and once estimated at 16m long (10m is more likely), ''Kronosaurus'' is named for Cronus, a Greek Titan who [[ImAHumanitarian devoured his own offspring]] (most of the Olympians among them). ''Liopleurodon'' was found in Europe in the late 19th century and was very similar to the former, but more primitive, slightly longer-necked, and with less teeth. As is usual with marine superpredators, both are usually depicted as [[PredatorsAreMean merciless ever-hungry]] [[PrehistoricMonster killing machines]].

Despite this, pliosaurs have been the least-portrayed group of sea reptiles, and still remain mainly creatures of documentaries. ''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. In the show, an old male ''Liopleurodon'' was described weighing 150 tons (a bit less than the blue whale) and the biggest predator of all time. In particular, the scene in which he chomps an ichthyosaur to pieces [[NightmareFuel disturbed many viewers]], though the sad final scene where he’s stranded like a whale and slowly dies is shown in a [[TearJerker very heartbreaking way]]. To give an 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.

For some reason, unlike dinosaurs and pterosaurs, marine reptiles are usually shown with dull colors even in modern portrayals. However, some of them might have been very colorful, like modern tropical seagoing animals. 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''.

Several interesting new pterosaurs were discovered in the second half of the 20th century: among them, ''Dsungaripterus'', ''Pterodaustro'', ''Tropeognathus'', ''Anhanguera'', ''Tapejara'', ''Eudimorphodon'', and the aforementioned "hairy" ''Sordes''; but only one managed to achieve some consideration in the media: ''Quetzalcoatlus'', because it was the only one clearly bigger than ''Pteranodon'', and the new "biggest flying animal ever." In the 2000s, ''Tropeognathus'' gained some popularity as well thanks to a memorable appearance in ''Series/WalkingWithDinosaurs'' (as "Ornithocheirus"), but only because it was (wrongly) described as the biggest flying animal that ever existed. In the 2010s, ''Hatzegopteryx'', found in year 2003 in Romania, also gained some fame thanks to its size, being possibly bigger than ''Quetzalcoatlus'' itself.

''Pteranodon''’s nifty crest, 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 could be partially justified. It’s not only one of the first-discovered pterosaurs, but perhaps also the most common in the fossil record. Hundreds of specimens are known, while most other pterosaur genera are much, much rarer, often known from a single individual. The vast majority of pteranodonts belong to the species everyone knows, ''Pteranodon longiceps'', the latter word meaning "long head" for its slender, pointy crest. The other species ''Pteranodon sternbergi'' had a somewhat more rectangular crest, which has lead some scientists to classify it as its own genus, ''Geosternbergia''.

''Quetzalcoatlus'' was not the only gigantic azhdarchid. Since the 90s others have been discovered with a similar estimated wingspan, e.g. ''[[http://en.wikipedia.org/wiki/Arambourgiania Arambourgiania]]''. But at an estimated 250 kg, ''Hatzegopteryx thambema'' was the heaviest of them, and quite possibly the [[GiantFlyer biggest pterosaur]] (and flying animal in general) of all time, a real "[[{{Badass}} Badassodactylus]]".

''Hatzegopteryx'' lived on and was named after the Late Cretaceous ''Hateg Island'' in Romania, where is today [[{{Dracula}} Transylvania]]. Here several dwarf true dinosaurs lived: dwarf titanosaur sauropods (''Magyarosaurus''), dwarf hadrosaur relatives (''Telmatosaurus''), dwarf ankylosaurs (''Struthiosaurus''), dwarf basal iguanodonts (''Rhabdodon''), small maniraptoran theropods (''Bradycneme''), but no big predatory dinosaurs due to the isolation. ''Hatzegopteryx'' was a peculiar creature for many reasons; while the island was home to dinosaurs that were subject to island dwarfism, ''Hatzegopteryx'' went the opposite direction and was subject to island gigantism. This would have put ''Hatzegopteryx'' on the top of the island's food chain. Additionally, unlike most other azhdarchids, ''Hatzegopteryx'' likely had an extremely thick and muscular build and a relatively short neck. This implies that ''Hatzegopteryx'' hunted significantly larger prey than other azhdarchids (potentially up to the size of a cow). For example, it could have swallowed a whole ''[[UsefulNotes/PrehistoricLifeAnkylosaurs Struthiosaurus]]'' armor included, which was an ankylosaur only 1.8 m long. Even though the hatzegopteryx 's wingspan was probably not wider than the one of ''Quetzalcoatlus'' or ''Arambourgiania'', its skull was much bulkier, and was probably as massive & long as the skull of a large theropod or ceratopsid dinosaur, and thus one of the biggest skulls among non-marine animals that ever existed.

''Hatzegopteryx'' is the most recent pterosaur to attain "stock" status, at least as far as nonfiction works are concerned (hence the one star above). Its current claim to fame is a memorable appearance in the documentary ''Series/PlanetDinosaur'', which ironically was made [[ScienceMarchesOn before the species' robust body plan was known]]. It has since appeared in ''VideoGame/TheIsle'', as an unlockable creature in ''Jurassic World: The Game'', and in 2022's docu ''[[Series/PrehistoricPlanet Prehistoric Planet]]'' (considered by many the "heir" of ''Planet Dinosaur'').

Among the numerous pterosaurs outside the classic five -- ''Pteranodon, Rhamphorhynchus, Quetzalcoatlus, Pterodactylus, Dimorphodon'' -- we might also mention the very short-named ''Sordes pilosus''. Even though its name is usually translated into "hairy devil", the genus name ''Sordes'' refers actually to a [[TheUnfairSex feminine]] mythical character of Central Asian folklore, and thus its species name should be rewritten ''pilosa'' (Latin feminine of hairy) according to some.

Very similar to ''Rhamphorhynchus'', this small (2 ft of wingspan) Late Jurassic "rhamphorhynch" from Kazakhstan, in the former U.S.S.R., has nonetheless had an enormous relevance in ptero-science; it was the first pterosaur ever discovered with ''fur-like covering'' (20 years before the description of the first feathered non-bird dinosaur), and thus led the start to the "[[ScienceMarchesOn Pterosaur Renaissance]]" briefly described in UsefulNotes/PrehistoricLifeDinosaurs. Today, many scientists believe all ornithodirans (= dinos + pteros + their common ancestors) were originally covered in filamentous skin structures - feathers and proto-feathers in the case of dinosaurs, "pycnofibres" in the case of pterosaurs. Both dinosaurs and pterosaurs could have inherited this trait from their earliest Triassic ancestors like ''Lagosuchus'' and ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Scleromochlus]]''. The other main archosaurian lineage, the pseudosuchians (crocs and their extinct relatives) never developed these filamentous elements on their skin during their evolution.

In paleo-art ''Sordes'' can be either shown with or without the classic ''Rhamphorhynchus'' fin on its tail, but is the ''only'' one among the pterosaurs found before the TurnOfTheMillennium that has always been shown "furred" and not naked or scaled like all the others (see also ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Avimimus]]'' for its non-bird-dinosaur equivalent). Some small ''Sordes''-looking pterosaurs are visible at the beginning of ''The Land Before Time'' film (made in 1988) together with other small reptiles of various kinds, after Littlefoot had just hatched.

The following extinct animals, to quote Lore Sjoberg, "are not technically speaking dinosaurs but end up in the dinosaur section of the plush toy aisle nonetheless."

In RealLife, pterosaurs were the dominant large flying creatures 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'' aspect of pterosaurian biology. 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 being 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 portrayed 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. While most media nowadays have done away with the bat wings, 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.

It's 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 would've meant pterosaurs were only awkward gliders — contrasting with the popular view of them as powerful fliers. Since the "renaissance" paleontologists now believe pterosaurs were the first ever vertebrates to be 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 metabolic rates. Due to the structure of their wings, pterosaurs would have been particularly adept at soaring (a bit like modern albatrosses), but they were also able to flap their wings.

Most pterosaurs discovered thus far appear to have lived in marine, coastal, or other watery habitats, but more dry land-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 may have been fruit-eaters. Some (especially ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Pterodaustro]]'') were flamingo-like filter feeders. Like dinosaurs, we don't know what coloration they had, though different kinds of pterosaurs surely had different colors. Modern artists often depict them with motifs reminiscent of those of modern birds, but may also portray them with duller colors (as happens with dinosaurs). Pterosaurs' locomotion on land has long been a mystery; their footprints were only first discovered in the 1990s. Scientists now think most or all pterosaurs were quadrupedal. Despite all these discoveries and theories, even today the pterosaurs remain one of the most enigmatic groups of prehistoric beasts, as their fossil record has always been one of the scarcest.

Sadly, all the issues above are usually glossed over in pop-media, even today.

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

Surprisingly, stock pterosaurs are ''not'' (necessarily) the biggest/coolest-looking ones — four out of seven are no bigger than an eagle or a stork. Instead, four of them were among the very first scientifically-described species, in the 19th century.

''Pterodactylus'', ''Rhamphorhynchus'', and ''Dimorphodon'' (all mid-sized) 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. Initially scientists were doubtful if pterosaurs were really fliers: since no modern reptile (in traditional sense) can fly, some thought they were ''swimmers'' using their membranes as flippers, while others believed they were terrestrial. And some, surprisingly, already postulated they were furry like mammals (even though most classical depictions show them scaly). The notion that they were covered with filamentous structures has re-emerged only since TheSeventies thanks to new fossil finds of that period (''Sordes'')

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 it still holds that status today.

Several interesting new pterosaurs were discovered in the second half of the 20th century: among them, ''Dsungaripterus'', ''Pterodaustro'', ''Tropeognathus'', ''Anhanguera'', ''Tapejara'', ''Eudimorphodon'', and the aforementioned "hairy" ''Sordes''; but only one managed to achieve some consideration in the media: ''Quetzalcoatlus'', because it was the only one clearly bigger than ''Pteranodon'', and the new "biggest flying animal ever." In the 2000s, ''Tropeognathus'' gained some popularity as well thanks to a memorable appearance in ''Series/WalkingWithDinosaurs'' (named "Ornithocheirus"), but only because it was (wrongly) described as the biggest flying animal that ever existed. In the 2010s ''Hatzegopteryx'', found in year 2003 in Romania, also gained some fame thanks to its size, possibly bigger than ''Quetzalcoatlus'' itself. If you’re looking for non-stock pterosaurs, see [[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles here]].

''Pteranodon'' lived 86-84 million years ago on what were then the shorelines of Kansas and other midwestern U.S. states. It had the typical traits of the most evolved pterosaurs, the pterodactyloids (aka literal pterodactyls). It had an elongated head, weak hindlimbs, only a hint of a tail, and very long wings with a huge "wing-finger," while the other digits were very small and may have been 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 may 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/PrehistoricLifeNonDinosaurianReptiles azhdarchids]] were known from fossils as late as 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 [[https://youtu.be/pQJIVxzIUic 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]]Astonishingly, short-crested pteranodonts are ''almost never'' shown even in documentary media![[/note]] This bony protrusion may have simply been a display device, as is hypothesized as well for ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Stegosaurus]]''’ plates, ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Triceratops]]''’ horns and frill, ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Spinosaurus]]''’ "sail," and so on. This could explain why the males’ one was so big compared with the females.

In popular portrayals, an ever-present mistake is to show ''Pteranodon'' as [[ToothyBird toothed]]. 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) may mislead people. Actually, ''odon'' is preceded by the Greek "privative ''a-''" (becoming ''an-'' when followed by a vowel). Thus, ''anodon'' means ''toothless'' (see also ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Ludodactylus]]'').

In RealLife, ''Pteranodon'' was basically a giant pelican in behavior. Its long toothless beak was useful for catching fish, and the shape of its lower jaws seem to show a sort of "pouch" to store fish in flight, 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 brown pelican; the other species of pelicans don't dive). If alive today, ''Pteranodon'' wouldn't be the danger for humans that it is in media. Weighing only about 20kg [[note]]For their body size, pterosaurs were even lighter than birds, having totally hollow bones like straws. For example, the prehistoric vulture ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Argentavis]]'' had a similar wingspan to ''Pteranodon'', but is estimated to have weighed 80kg.[[/note]], it was too light to lift a 70kg man off the ground. And even if it could have done so, it wouldn't have used its weak hindlimbs, but its mouth instead. Finally, since its beak was straight and smooth-edged, a child could easily have escaped 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 could be partially justified. It’s not only one of the first-discovered pterosaurs, but perhaps also the most common in the fossil record. Hundreds of specimens are known, while most other pterosaur genera are much, much rarer, often known from a single individual. The vast majority of pteranodonts belong to the species everyone knows, ''Pteranodon longiceps'', the latter word meaning "long head".

''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 ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Archaeopteryx]]'' and ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Compsognathus]]''. It was the second named pterosaur after the prototypical ''Pterodactylus'' (see below), 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 [[note]]Even though classic portraits show it with a straight snout[[/note]], 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 relative ''Sordes pilosus'' (which just means "hairy devil").

Its striking look, the earliness of its discovery 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''. And Harryhausen's movie Film/OneMillionYearsBC shows a huge, short-tailed (and tailfin-lacking) rhamphorhynch winning an aerial battle against an equally huge (but correctly toothless just for once) pteranodont. 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 the "raptor" dinosaurs) and often ending with ''triangular, arrow-like fins'', like [[https://youtu.be/bENtOFR66YY here]]. 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 "dragonish" rhamphorhynchoid tail to [[RuleOfCool every other]] [[MixAndMatchCritter pterosaur]], especially ''Pteranodon''. Actually, pterodactyloid pterosaurs had stubby tails without distinction. Some specialized rhamphorhynchoids had also short tails, like the tiny ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Anurognathus]]''.

This has been considered 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 northropi'' 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 "[[FeatheredDragons feathered snake]]" - the animal itself is often called "the quetzalcoatl". Its name also recalls that of the modern [[http://en.wikipedia.org/wiki/Quetzal Quetzal]], the long-tailed bird who was sacred to the Aztecs. In 2021, a second smaller-sized ''Quetzalcoatlus'' species, ''Quetzalcoatlus lawsoni'', was described.

Weighing about 80 kg like an adult human, ''Quetzalcoatlus'' was long described as similar to an upscaled ''Pteranodon'' (which weighed less-than-half). 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 been 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 [[http://pterosaurs.wordpress.com/2008/05/16/azhdarchid-paleobiology-part-i/ as tall as a giraffe]] when on land, ''Quetzalcoatlus'' could still ''fly'' -- even though some scientists still doubt that such a large critter could actually take off. If it really was a flier, 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 more menacing, with a more muscular frame and a shorter neck.

Despite its impressiveness, ''Quetzalcoatlus'' has only received great attention in dino-books and documentaries, while is still rare in films and dino-stories (the recent appearance in 2022's ''[[Film/JurassicWorldDominion Jurassic World Dominion]]'' could change it, however). No matter that, with its size and terrestrial habits, it could have been the ''only'' of the classic five stock pterosaurs 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 (a case of ScienceMarchesOn). Another less-complex flying robot built in the same years represented ''Pteranodon''.

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 — 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 have traditionally been common in documentary 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'' ("ancient winged finger"), 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 very recent discovery (made in the 2000s) 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/PrehistoricLifeNonDinosaurianReptiles Pterodaustro]]'') or perhaps a wader/prober like a shorebird. ''Ctenochasma elegans'', a close relative of the same habitat, was once classified as ''Pterodactylus elegans'', and its name means "elegant comb-jaw". Once, some dubious Jurassic pterosaurs found in Tendaguru (Tanzania) were considered ''Pterodactylus'' and ''Rhamphorhynchus'' specimens.

''Dimorphodon'' was a rhamphorhynchoid that lived in Early Jurassic, 190 mya - the most ancient of the stock pterosaurs. 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/PrehistoricLifeNonDinosaurianReptiles 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 (naturally in the [[DeathFromAbove "winged menace"]] role).

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

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

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

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

''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).

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

''Sarcosuchus imperator'' ("Emperor meat-eating croc") lived earlier than ''Deinosuchus'', in the Early Cretaceous. It was found originally in Brazil and named ''"Crocodylus (a modern crocodile genus)"'' ''hartii'' in 1869, but it was only recognized as a new genus from remains found a century later in Niger, together with some dinosaurs like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Ouranosaurus]]'' that could have been its prey. It was still too primitive to be an Eusuchian, but resembled one in shape: with its long thin jaws, it recalled closely the modern [[http://en.wikipedia.org/wiki/Gavialis_gangeticus gharial]] of India. It was about the same size of ''Deinosuchus'' but slenderer; some remains from South America are also known possibly belonging to it or to a close relative. Like ''Deinosuchus'', its lifestyle is only a guess.

''Sarcosuchus imperator'' ("Emperor meat-eating croc") lived earlier than ''Deinosuchus'', in Early Cretaceous, and was found originally in Northern Africa in the 1970s together with some dinosaurs like ''[[UsefulNotes/StockDinosaursOrnithischianDinosaurs Ouranosaurus]]'' that could have been its prey. It was still too primitive to be an Eusuchian, but resembled one in shape: with its long thin jaws, it recalled closely the modern [[http://en.wikipedia.org/wiki/Gavialis_gangeticus gharial]] of India. It was about the same size of ''Deinosuchus'' but slenderer; some remains from South America are also known possibly belonging to it or to a close relative. Like ''Deinosuchus'', its lifestyle is only a guess.

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.

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

#'''Entry Time:''' 1996
#'''TropeMaker:''' ''Literature/ASongOfIceAndFire''

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

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

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

Similarly, these animals are often collectively referred to as "marine dinosaurs," but this time they were ''not'' close relatives of true dinosaurs; some of them were not even related to each other. There ''were'' semiaquatic 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.

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

''Archelon ischyros'' lived in the Late Cretaceous inland shallow sea which once covered the Great Plains of the U.S. 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 — though in [[Franchise/WalkingWithDinosaurs WWD]] an ''Archelon'' is shown killed by a giant mosasaur, but the latter was oversized.

# '''TropeMaker:''' The ''Franchise/WalkingWithDinosaurs'' franchise and ''WesternAnimation/TheLandBeforeTime'' sequels

# '''TropeMaker:''' Popular prehistory media (''Cynognathus''), ''Franchise/WalkingWithDinosaurs'' (''Thrinaxodon''),

# '''TropeMaker:''' ''Franchise/WalkingWithDinosaurs''

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

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

# '''TropeMaker:''' ''Series/WalkingWithBeasts''

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

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

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

Among the numerous pterosaurs outside the classic FiveManBand made of ''Pteranodon, Rhamphorhynchus, Quetzalcoatlus, Pterodactylus, Dimorphodon''[[note]]''Pteranodon'' is TheLeader (because of its large size, its "royal" headcrest and its large popularity among casual people); ''Rhamphorhynchus'' is TheLancer (because has been the 2nd most famous pterosaur, and was smaller but more aggressive-looking than ''Pteranodon'' thanks to its teeth and tail); ''Dimorphodon'' is TheSmartGuy (because of its big head and small body-size); ''Quetzalcoatlus'' is TheBigGuy (because of its overall immense size and strength); and ''Pterodactylus'' is TheChick (because is probably the most harmless of the five, with its small teeth)[[/note]], we might also mention the very short-named ''Sordes pilosus''. Even though its name is usually translated into "hairy devil", the genus name ''Sordes'' refers actually to a [[TheUnfairSex feminine]] mythical character of Central Asian folklore, and thus its species name should be rewritten ''pilosa'' (Latin feminine of hairy) according to some.

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

Before the discovery of ''Lagosuchus'' in the 1970s, other "thecodonts" were considered the direct ancestors of dinosaurs, especially the European ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Saltoposuchus]]'' ("hopping-footed croc") and to a lesser degree ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Scleromochlus]]''[[note]]The latter could be an ancestor of pterosaurs, though.[[/note]] — and some were often even considered early proper dinosaurs (more precisely early theropods), notably the 12 ft long ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Ornithosuchus]]'' ("bird-croc"), the 2 ft long ''[[UsefulNotes/PrehistoricLifeOtherSmallTheropods Saltopus]]'' ("hopping foot"), and the large, 20 ft long ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Teratosaurus]]''. Actually, ''Ornithosuchus'', ''Teratosaurus'' and ''[[NamesTheSame Saltop]]osuchus'' [[note]]but not ''[[NamesTheSame Saltop]]us'', a close dino-relative like ''Lagosuchus''[[/note]] were more closely related to crocodilians than to dinosaurs or pterosaurs; the same is true of the Rauisuchians and Aetosaurs above. Phytosaurs, on the other hand, were long believed to be direct crocodile ancestors, but according to [[ScienceMarchesOn recent research]] they are not even archosaurs sensu stricto, just like ''Euparkeria''.

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

Not all Mesozoic reptiles were exotic by modern standards. ''Archelon'' was simple a sea turtle. But it perfectly fits the subtrope that 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 [[http://en.wikipedia.org/wiki/Dermochelys_coriacea 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).

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

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

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.

The lesser-known belemnites (technically belemnoids), with their straight pointed shape, were believed to be stony arrows, or even the Devil's fingers! Belemnites were cephalopods living in the Mesozoic era together with ammonites, and probably gave rise to squid. Like ammonites, only their shells are usually preserved. This shell was straight and often arrow-shaped, and was ''inside'' the animal's body and invisible in life; belemnites would resemble simple squid or cuttlefish if alive today. Their lifestyle was more active than ammonites, and they were probably able to do the same things modern squid do: spraying ink, swimming using the lateral "fins", catching prey with their suckers, seeing images with their eyes. In popular media belemnites tend wrongly to be portrayed or described as proper squids, but technically they weren't. They too tend to be show as ambient animals for mesozoic or prehistoric placements.

As a group, trilobites lived through the whole Paleozoic era, but became rarer and rarer after the Devonian, and none survived the devastating Permian-Triassic mass extinction: thus, they might taken as the Paleozoic's unofficial symbol. Though their appearance could lead to them being confused with insects or crustaceans, they were actually not related to any modern arthropod. They are classified in between the two main arthropod groups: chelicerates (arachnids + sea spiders + horseshoe crabs) and mandibulates (hexapods + myriapods + crustaceans).

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

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

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

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

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

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

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

Despite this critter's size and appearence, ''Arthropleura'' historically got little presence in the media, but in recent years it's become a common sight in paleo-books and documentaries about life before the dinosaurs. The most noteworthy appearance of an ''Arthropleura'' in a non-educational work was ''Series/{{Primeval}}'', which [[RuleOfCool for some reason]] decided to portray it as a giant venomous ''centipede''.

The potential interest toward them is tied to their size: ''Pterygotus'' was as long as a grown human; ''Cameroceras'' was much longer, as long as the armored fish ''Dunkleosteus''. They were the top predators of their seas (Silurian and Ordovician respectively). At a first glance, however, their appearence, though rather unusual by modern standards, wasn't so different from that of modern crustaceans and octopuses. The pterygotus resembled a slender lobster with big insect-like eyes and curious rear legs similar to paddles, for swimming; the "orthocone" resembled a squid inside an ice cream cone-like shell, though probably with more tentacles. MixAndMatchCritter fits well with both of them.