History UsefulNotes / StockDinosaursOrnithischianDinosaurs

''Styracosaurus'' frill spikes were ''not'' true horns as commonly said, but only an exaggerated version of those protuberances commonly seen in ceratopsid species. Even though the most common portrayal has six spikes, it seems most specimens had only ''four''. But don't rule out seeing styracosaurs with eight spikes (like in Disney's ''WesternAnimation/{{Dinosaur}}'') or more in popular works, or even with no frill and the spikes protruding directly from the back of the neck like the horned lizard of the deserts of North America. Interestingly, another modern species of lizard, the Jackson's chamaeleon of Africa, has three horns and a frill very reminiscent of ''Triceratops'', and the cowl of the Australian frilled lizard kinda resembles a ''Triceratops'' shield when open.

''Torosaurus latus'' was described during the Bone Wars by Marsh as a distinct ceratopsid genus from ''Triceratops''. It was basically identical to the latter, only with a much longer frill that reached the shoulders when held horizontally: this shield was smooth-edged and with the typical two openings hidden by skin in life. ''Triceratops'' lacked these openings: indeed, "Torosaurus" means "open lizard" precisely because of this, and ''not'' "bull lizard" as stated in many sources. ''Toro'' means "bull" in Spanish and Italian, but the Latin word is ''taurus'' (from which comes the French word ''taureau''). The torosaur lived in the same places and epoch as ''Triceratops'', the extreme Late Cretaceous North America, but its fossils have always been rarer than the latter.

In 2010, some scientists proposed that ''Torosaurus'' may not have been its own genus at all, but instead may have simply been the mature form of ''Triceratops''. This, naturally, led to a number of ill-informed Internet articles claiming that ''Triceratops'' was somehow invalid. However, thanks to how scientific names work (if two different names are given to a species, the first one is the one that stays valid), this is impossible; instead, the name ''Torosaurus'', created a few years after the name ''Triceratops'', would be retired and ''Triceratops'' would remain in use. In any case, there is still good reason to believe that ''Torosaurus'' is a valid species. ''Torosaurus'' fossils have been found in areas where ''Triceratops'' fossils have not, and at least one sub-adult ''Torosaurus'' specimen is known.

Known since the first half of the 20th century from remains discovered in New Mexico, ''Pentaceratops'' gained more attention in the 1990s after the discovery of a gigantic skull which was attributed to its genus. Before that, ''Torosaurus'', with its 2.5m-long skull, bore the record for the biggest-headed land animal ever; this putative ''Pentaceratops''' skull was ''3 m long''. [[ScienceMarchesOn Science Has Marched On]] however, and this specimen has been deemed a separate animal in January 2011, meaningfully named ''Titanoceratops'' (although there are still those who maintain it's just a large ''Pentaceratops''). ''Pentaceratops'' has appeared in the video game ''VideoGame/JurassicWorldEvolution'' as one of the cloned dinosaurs in the park.

The TurnOfTheMillennium saw a sudden increase in ''Pachyrhinosaurus'' appearances in pop culture, starting as a background character in Disney's ''WesternAnimation/{{Dinosaur}}'', then as a major character in ''[[WesternAnimation/TheLandBeforeTimeVIIITheBigFreeze The Land Before Time 8]]'', and then as the lead role in the ''Film/WalkingWithDinosaurs'' film. It was, at one time, planned to appear in ''Film/JurassicWorldFallenKingdom'', but was replaced with the much more obscure ''[[UsefulNotes/PrehistoricLifeCeratopsids Sinoceratops]]''. ''Series/PrehistoricPlanet'' prominently features a herd of bristly ''Pachyrhinosaurus'' being menaced by a trio of ''Nanuqsaurus'' in the midst of a huge blizzard. It seems its oddness among the "classic" ceratopsids has contributed to this formerly unexpected success. Some part of its prominence can also be contributed to specimens being found in Arctic fossil deposits, leading some to imagine it as the dinosaur equivalent of the woolly mammoth or woolly rhino, complete with a speculative coat of insulating down.

Anyway, "Stygimoloch spinifer" did get a memorable scene in ''Film/JurassicWorldFallenKingdom''; it's worthy to be noted that film consultant Jack Horner advised against featuring the "Stygi" due to the above controversy, but was overruled by the filmmakers. But its first apparition in cinema is in 2000's Disney's ''WesternAnimation/{{Dinosaur}}''. Talking about "Dracorex hogwartsia", our "[[Franchise/HarryPotter harrypottersaur]]" is one of the few real nonbird dinosaurs portrayed in the TV series ''Series/{{Primeval}}'', even though in a [[ArtisticLicensePaleontology quite fanciful way]], with an [[DinosaursAreDragons actual dragon-like crest]] on its back. ''Pachycephalosaurus'' also showed up in the second season of ''Series/PrehistoricPlanet'', using its famous dome to show off to rivals before engaging in a fight that's equal parts headbutting and flankbutting.

Like the [[AquaticSauropods sauropods]], hadrosaurs were associated with [[AquaticHadrosaurs water]] in pre-Renaissance times. Indeed, the sauropods and the hadrosaurs were once considered the two amphibian lineages of dinosaurs -- all the other dinosaurs were considered adapted for a land-living style. Why? Because the early discovery of some mummified hadrosaurs whose skin on their hands was believed to be remnants of webbing made scientists believe they were semi-aquatic creatures with literally duck-like webbed hands -- not because they were thought too heavy to sustain their bulk on land, unlike the giant sauropods. [[ScienceMarchesOn We know now]] this skin bound the fingers together into a single, toughened "hoof" apt for walking on dry soil. Also, when on land, hadrosaurs were once shown assuming the same upright posture of an old-fashioned theropod. After the Renaissance, scientists described hadrosaurs as terrestrial animals, similar to modern ungulates but capable of shifting from a quadrupedal to a bipedal posture. Needless to say, amphibious hadrosaurs with webbed hands and upright stance still appear in recent media (see ''WesternAnimation/TheLandBeforeTime'').

This dinosaur has appeared in almost every dino-film, but usually in minor roles -- basically with the sole purpose of increasing the variety of the "dinosaur world". And don't expect to hear its name, either -- even though it's not one of the shortest dino-names, it remains cool-sounding anyway. A good example is in the ''Franchise/JurassicPark'' films. Some ''Parasaurolophus'' are visible behind the ''Brachiosaurus'' in the famous "Welcome to Jurassic Park!" scene of the first film; they are also seen in every following sequel, too. But all these were simple cameos, and the animal is never named. (One character does make an attempt in the 2nd movie, but gives up fairly quickly.) Other unnamed appearances are in Disney movies -- ''WesternAnimation/{{Fantasia}}'' (where they have the old upright pose and a huge flap of skin between the crest and the neck) and ''WesternAnimation/{{Dinosaur}}'' (where are more modern-looking). One rare example of a major-character ''Parasaurolophus'' is seen in ''WesternAnimation/TheLandBeforeTime''... at least, Ducky and her parents are officially labeled as such: they're actually based on its distant relative ''Saurolophus''.

''Edmontosaurus'' is one of the most scientifically known dinosaurs, with more than ''10,000'' known specimens (most other dinosaurs have less than 100 known specimens, but usually much fewer) showing every detail about its life, even diseases like cancer or fractures. The most striking ones are the "petrified mummies" (all of ''E./A. annectens''), which have preserved not only skin prints, but also ''hardened muscles''. If you don't believe us, [[http://en.wikipedia.org/wiki/Trachodon_mummy see]] [[https://en.wikipedia.org/wiki/Edmontosaurus_mummy_SMF_R_4036 them]] [[http://en.wikipedia.org/wiki/Dakota_(fossil) here]]. The third find shows an unexpected thing: hadrosaurs had a much more massive tail than traditionally thought. If this'd be true for all dinosaurs, then [[ScienceMarchesOn many classic studies about dinosaur biomechanics should be reviewed]]. For example, hadrosaurs and their kin are often thought mainly quadrupedal, but a heavier tail would make their center of gravity just under their hips, perfectly balancing their body on two legs. Maybe hadrosaurs mainly walked on two feet and walked on all fours only when grazing, drinking or resting, like kangaroos -- a possible proof of this is that most hadrosaur and iguanodont tracks seemingly do not show prints of forelimbs. Interestingly, Mummy #3 also tells us hadrosaurs were much faster than previously thought, up to speeds of 45km/hr.

"Trachodon" first appeared in pop-media in 1925 (''Film/TheLostWorld'' film adaptation), in which it's portrayed as prey for a giant carnivore. After that, it became THE duckbill in the public consciousness, to the point where "trachodont" was also used as a popular synonym of "hadrosaur" (a bit like how "brontosaur" was a synonym of sauropod). After 1990 however, "Trachodon" rapidly disappeared from pop-consciousness -- although its ghost is still seen from time to time. Meanwhile, "Anatosaurus" experienced a surge in popularity during the Dino-Renaissance and became the most widely-used name in pop-culture until the 90s popularized "Anatotitan", mainly thanks to ''Series/WalkingWithDinosaurs'' (which acknowledged the possibility of it being the same as ''Edmontosaurus annectens'' in the companion book some 10 years before it was proven true). But after "Anatotitan" was sunk into ''Edmontosaurus annectens'', ''Edmontosaurus'' has been growing in popularity, albeit primarily in docu-media. "Anatotitan" and "Anatosaurus" still appear semi-regularly though, with the latter being used in ''VideoGame/{{Saurian}}'' as an informal name for ''E. annectens''.

That said, ''Edmontosaurus'' hasn't gone an especially long way in non-docu media: when ''Edmontosaurus'' appears, it's simply known as a "duckbill," and the crested ''Parasaurolophus'' has become the most portrayed hadrosaur in fiction today (probably because of the crest and the less convoluted backstory). ''Edmontosaurus/Anatosaurus annectens'' is also ''much'' more common in documentaries than ''Edmontosaurus regalis'', and for good reason: With the possible exception of ''Hypacrosaurus'' (see below), ''E./A. annectens'' is the only hadrosaur known from the same time and place as ''Tyrannosaurus'', ''Triceratops'', and the other famous dinosaurs from the end of the Cretaceous. Therefore, if a work is showing the end of the Cretaceous and wants to be accurate, this is usually the hadrosaur they'll use. ''E. regalis'' tends to show up much more in popular dino-books by contrast. Additionally, the unnamed Alaskan ''Edmontosaurus'' we briefly brought up at the start has shown up in the ''Film/WalkingWithDinosaurs'' movie and ''WesternAnimation/MarchOfTheDinosaurs'', albeit mostly identified with ''E. regalis''.

This hadrosaur deserves a special mention. The same size of ''Parasaurolophus'' and contemporary to it, 76-74 mya, ''Maiasaura'' did not have the striking headgear of it (only a small relief above the eyes), nor did it have such a wide bill like ''Edmontosaurus''. Nonetheless, it has been one of the most important dino-finds ever.

Hundreds of ''Maiasaura''s were discovered together in Montana in 1980 by famous paleontologist [[http://en.wikipedia.org/wiki/Jack_Horner_(paleontologist) Jack Horner]] (better known as the ''Franchise/JurassicPark'' official consultant, and also for having defended against colleagues the unpopular "scavenging T. rex" theory in some TV apparitions), in what is known today as the "Egg Mountain" -- at that time a small lake-island. His mountain showed not only adults, but also many fossilized, 6 ft wide, crater-like nests made of earth and full of hadrosaurian eggs, hatchlings of all ages, and even skeletons of ''embryos'' still inside the eggshells!

Before the 1980s only few dinosaurian eggs were known to science: those of ''Protoceratops'', oviraptorids, "Hypselosaurus", ''Psittacosaurus'', and few others, and parental caring among dinosaurs was still a very speculative issue. Horner's discovery was a true snapshot of daily dino-life. He noted that the youngest specimens still had incomplete limb-bones: this meant they were incapable of leaving their nests. And yet, their teeth were noticeably worn, as they were already eating tough vegetation. How could they feed on themselves? ''Here'' is the proof of parental care: only adult ''Maiasaura'' could have fed the young such plant matter until they grew large enough to finally leave their nest. Horner gave a MeaningfulName to his caring dinosaur: ''Maiasaura peeblesorum'' means "Peebles' good mother lizard" (note the unusual feminine suffix ''-saura''). It was his deep study of this dinosaur and its parenting habits that gave Horner his prestige in the scientific community.

Horner and other scientists have since made a possible reconstruction of the ''Maiasaura'' lifestyle. [[SocialOrnithopod Huge herds of possibly up to 10,000 individuals]] used to migrate across Western North America from Canada to Montana for wintering at their nesting islands. Here, they mated, built their nests, laid their eggs, and filled their nests with decaying vegetation to keep the precious eggs warm: remains of fossilized rotting plant material have been found in these nests (being too heavy adult ''Maiasaura''s didn't brood their eggs like modern chickens do.) After the hatching, adults fed their helpless babies good food, moved by their cute appearance: the babies' skulls show large eyes and short muzzles like modern mammal cubs. After developing their skeletons, the youngsters started to search for food on their own; finally, the whole herd undertook again their migration once more. In short, an overall behaviour ''very'' similar to many modern migrating birds.

This reconstruction made the top of the Dinosaur Renaissance, definitively debunking the old [[DumbDinos big, stupid, unfeeling, oafs]] thing, and making ''Maiasaura'' just as common in popular books as ''Parasaurolophus'' and ''Edmontosaurus''. However, ''Maiasaura''s inconspicuous appearance was [[RuleOfCool not interesting enough]] to earn it any movie appearances. Even though the "good mother dinosaur" and the whole argument around are often mentioned in the first ''Franchise/JurassicPark'' novel (which, by the way, had Horner as the consultant), this was totally overlooked in Creator/StevenSpielberg's following film. Other Hollywoodians resolved the problem in another way: giving ''Maiasaura'''s behaviour to other dinosaurs. In ''WesternAnimation/TheLandBeforeTime'' for instance, all the herbivorous dinosaurs migrate through the lands and hatch their young in crater-like nests made of earth. All OK? Not really. It's like saying ostriches and penguins build cup-like nests just because songbirds build cup-like nests. In fact, evidence suggests some dinosaur groups, like the sauropods, did not take care of their young at all, and other would have likely practiced different styles of parenting. However, our knowledge of dinosaur parenting in most groups is still incomplete and a lot of their behaviors remain speculative.

In TheNewTens, ''Maiasaura'' finally made its first notable film appearance in the Japanese animated movie ''Anime/YouAreUmasou'' where it's shown to live up to the "Good Mother" in its name, taking in an orphaned ''Tyrannosaurus'' and lovingly raising it as its own along with its biological children, a bit like the songbirds that adopt unwillingly cuckoo chicks. Before, the ''Maiasaura'' had also appeared ''Series/DinosaurPlanet'' as one of the protagonists alongside the tyrannosaur ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Daspletosaurus]]'', as well as an episode of ''WesternAnimation/TheMagicSchoolBus'' as one of the dinosaurs encountered by Ms. Frizzle and her students on a TimeTravel field trip to Late Cretaceous North America.

Hadrosaurs were very diverse in RealLife. Even though they all shared the same body-plan, their heads were ''wildly'' different between species. They are divided in two main lineages: the lambeosaurines (those with hollow crests, like ''Parasaurolphus'') and the saurolophines (those without, such as ''Edmontosaurus'' and ''Maiasaura''). Other than ''Parasaurolophus'', the only lambeosaurine with a significant number of appearances in pop-media is ''Corythosaurus''. Naturally, the latter has been a rarer sight. In the ''Franchise/JurassicPark'' film series, ''Corythosaurus'' joins ''Parasaurolophus'' only in the third film. Just like ''Parasaurolophus'', good luck ever hearing ''Corythosaurus'' get named in fiction. Compensating this, it has been just as common as ''Parasaurolophus'', ''Maiasaura'', and ''Edmontosaurus'' in documentary works, which regularly show it with its distinctive crested look.

''Corythosaurus'' was slightly smaller than ''Parasaurolophus'' (7-9 m long), and lived in Late Cretaceous North America about 77-75 mya. A classic error in paleo-art is to depict these two dinosaurs living alongside ''Tyrannosaurus rex''. Since the "rex" was discovered in more recent terrains (68-66 mya), this makes a slight AnachronismStew case. If the artist did the research these two hadrosaurs will interact with other smaller tyrannosaurids like ''Daspletosaurus'' or ''Gorgosaurus''.

A frequently ignored fact about hadrosaurs was that they were the biggest plant-eating non-sauropodian dinosaurs. The most massive species were [[https://youtu.be/rRiecAmGWHU taller, longer and heavier]] than even the largest ceratopsians, stegosaurs, or ankylosaurs. And though not necessarily taller/longer, thanks to their massive bodies, they were heavier than giant theropods like ''Tyrannosaurus'' and maybe even ''Spinosaurus'' itself! But which one was the record-holder?

Discovered in the 1970s, ''Shantungosaurus giganteus'' ("gigantic Shandong lizard", from the Chinese province it was first found) was quite similar to ''Edmontosaurus'', and usually believed closely related with it. However, it was bigger than the latter, the same size of the aforementioned "giant lambeosaur" ''Magnapaulia'' (15m/50ft long and 12 tons or more in weight). Despite the fact they rivalled certain sauropods in size, neither hadrosaur has received any attention in fiction yet, although they are staples of dino-books. Both subfamilies of duckbills, the lambeosaurines and saurolophines, have members both in Asia and in North-America -- giving more proof of a connection between the two landmasses in the Late Cretaceous by the today-Bering Strait.

Few other dinosaurs have had such a tormented ScienceMarchesOn story like that of ''Tsintaosaurus''. It was initially described from fragmentary remains that seemed to show a single horn-like crest pointing forward and upward upon its head like a unicorn's horn. Said crest was often shown with [[DoesThisRemindYouOfAnything a pair of small speculative airsacs at the base of its long, thin, rod-shaped crest]]. Then, scientists took the crest away in the 1990s, thinking it was actually a misplaced piece from the rest of its skull, with some even hypothesizing that ''Tsintaosaurus'' was the same as another less-known Asian duckbill, the crestless saurolophine ''[[http://en.wikipedia.org/wiki/Tanius Tanius]]''. However, a later find to show that ''Tsintaosaurus'' really did have a crest... until a 2013 study showed the "horn" was just a fragment from a ''backwards''-pointing crest, looking a bit like that of its also-Asian relative ''[[UsefulNotes/PrehistoricLifeHadrosaurs Olorotitan]]'' but more elongated.

In old books, ''Kritosaurus'' used to be shown as one of the prototypical hadrosaurs, along with "Anatosaurus", ''Parasaurolophus'', ''Corythosaurus'', and ''Saurolophus'', and their skulls were often shown together making a sorta [[FiveManBand Five Hadro Band]]. This "band" has also appeared once in cinema: in 1940, the "Rite of Spring" of ''WesternAnimation/{{Fantasia}}'' portrayed all but one member -- but the missing one was ''Saurolophus'', not ''Kritosaurus''. More precisely, the kritosaur is the one with the bulged-nose: this sort of "Roman nose" has often been cited as the origin of its name, "noble lizard", though the real meaning of "krito-" is uncertain. The classic species of ''Kritosaurus'' is ''K. navajovius'', after the Navajo people.

''Hadrosaurus'' was the very first dinosaur ever identified as such in North America (and outside of Europe) from more remains than simple isolated teeth, as early as in year 1858. Like most early discoveries, ''Hadrosaurus'' has a generic-meaning name, "heavy lizard". Oddly for a US dinosaur, it was found in New Jersey -- dinosaur remains are extremely rare west of the Mississippi. In fact, dino-discoveries in EagleLand began in the East Coast, and it was only with the start of the "Bone Wars" did the American West become more important; one could call it a veritable Dino-Rush -- fossil of dinosaurs are true ''gold'' for paleontologists, also because of their rarity.

Living 126 to 122 million years ago in Early Cretaceous Europe, this is one of the most iconic non-avian dinosaurs from the "old continent" together with ''Compsognathus'', ''Plateosaurus'', ''Megalosaurus'', ''Baryonyx'', and to an extent, ''Archaeopteryx''. It's also one of the most scientifically well-known dinosaurs, and one of the most abundant in the fossil record. ''Iguanodon'' has had a special role within the stock dino-ensemble. Along with ''Megalosaurus'' and ''Hylaeosaurus'', it's the only dinosaur that has covered the whole history of scientific and popular portraits, but unlike the rarely-portrayed-these-days megalosaur & hylaeosaur, ''Iguanodon'' is still pretty common today in pop-media.

Although nearly as big as ''Tyrannosaurus'' (10 m or more, and up to 4 tons), ''Iguanodon'' has not an especially striking look among Stock Dinosaurs. Being an earlier relative of hadrosaurs and possibly their ancestor, its shape resembled one of the latter, with three-toed hindfeet, a flexible neck (but less so than hadrosaurs), a long muscular tail stiffened by bony tendons, a massive body, and hindlimbs longer and stronger than forelimbs. Non-hadrosaurian traits include: the backbone not being curved at the shoulder level; grinding teeth much less numerous and put in one single row on each half-jaw like almost all non-hadrosaur dinosaurs; a totally crest-less, bump-less head; and a deep, narrow beak very unlike the duck-billed one.

The hands of ''Iguanodon'' contain all the "oddities" in its skeleton. The best known is the [[HookHand spike on its hand]], made of the first digit's phalanxes fused together and encapsulated in a horny sheath, usually shown in books as a weak weapon against enemies. It also had a very flexible, opposable "pinkie" finger, maybe to grasp vegetation. Hadrosaurs too had a little-finger in their hands other than the three main digits, but was smaller than the ''Iguanodon'''s one and maybe useless and vestigial. Like hadrosaurs, the three central fingers of ''Iguanodon'' were fused together in a hoof-like structure and supported the weight of the dinosaur when on four legs, though incorrect freely-fingered iguanodonts and hadrosaurs often appear in portraits.

We don't know for sure if iguanodonts and hadrosaurs were mainly tree-browsers or ground-grazers. However, classic portraits usually show iguanodonts in the usual "tripodal" stance and browsing like a giraffe. Several paleo-works have also added a long extendable giraffe-like tongue to reach tree foliage, but this is unlikely. In these old portraits, ''Iguanodon'' was substantially the reptilian equivalent of the giant ground sloth ''[[UsefulNotes/StockDinosaursNonDinosaurs Megatherium]]'', also often portrayed as an upright tree-browser with a horsey head, robust clawed forelimbs, a giraffe-tongue, and a tail used as a tripod together with the hindlegs.

''Iguanodon'' is one of the three animals along with ''Megalosaurus'' and ''Hylaeosaurus'' called "dinosaurs" for the first time in history (1842), by the infamous English paleontologist [[http://en.wikipedia.org/wiki/Richard_Owen Richard Owen]]. ''Iguanodon'' was already identified in 1825, just one year after ''Megalosaurus'', by English doctor and fossil collector Gideon Mantell: it's the second non-bird dinosaur to have received an official name. It was initially described from its iguana-like teeth and a few other incomplete remains: hence its name meaning ''iguana's tooth''. But then, in 1877 [[SocialOrnithopod about 40]] ''Iguanodon'' skeletons were discovered within a coal mine in Belgium near the town of Bernissart, the very first "dino graveyard" ever found. These remains were named ''Iguanodon bernissartensis'' and described by Belgian zoologist Louis Dollo. Many other remains were later assigned to ''Iguanodon'', often found outside Europe and across the full timespan of the Jurassic and Cretaceous. Most have since been split in other genera, making it a wastebasket taxon much like the more classic "Megalosaurus wastebasket". Among these genera include ''Hypselospinus'', ''Dakotadon'', ''Altirhinus'', ''Cumnoria'', ''Mochlodon'', and ''Mantellisaurus'', the last of which was named after Gideon Mantell.

Most dinosaurs have changed their look at least once: ''Iguanodon'' has done this ''twice''. The first attempt at reconstruction showed [[http://www.places-to-go.org.uk/crystal_palace_iguanodon.htm a huge dragon-like quadruped]], and one of its thumbspikes was inaccurately put on its nose -- this is justified by the very fragmentary nature of its original remains. The life-sized ''Iguanodon'', alongside ''Megalosaurus'', ''Hylaeosaurus'', and other extinct animals (including Ice Age megafauna, marine reptiles, and pterosaurs), were sculpted by Benjamin Waterhouse Hawkings and shown to the public during the 1856 Universal Exposition in London, at the famous Crystal Palace. A banquet was organized to celebrate the event... inside the still incomplete iguanodon model! Even though the palace was ultimately destroyed by a fire, the sculptures survived the incident, and are still visible at the eponymous park.

After the discovery of the complete skeletons from the Belgan "dinosaur mine" in the 1870s, the ''Iguanodon'' became [[https://youtu.be/pQJIVxzIUic bipedal and upright, but still reptile-looking]], often shown with iguana-spikes running along its back, and with an overall theropod appearance. Finally, studies started in the 1970s and led by English paleontologist David Norman made Iguanodon quadrupedal again (though still capable of standing and running on two legs), with cheeks hiding the teeth in the living animal.[[note]]Once, all ornithischian dinosaurs were portrayed with no cheeks and a wide mouth running from ear to ear, like saurischian dinosaurs: this was based on modern reptile, which are unvariably cheek-less. The shape of ornithischian jaws showed they could have had cheeks to store plant matter during mastication, like modern herbivorous mammals. This is confirmed by the "hadrosaur mummies." If alive today, an ornithischian's head would resemble a hairless [[MixAndMatchCritter ungulate with a beak]].[[/note]] An excellent example of this new portrait is seen in Disney's ''WesternAnimation/{{Dinosaur}}'', which made ''Iguanodon'' the main character in the story -- [[ExecutiveMeddling exaggerating its horse-like look]] with fleshy lips instead of the proper bill, and showing it always running on all fours like an actual horse.

Even though it has been extremely common in dino-books and other non-fictional media, ''Iguanodon'' did not make any significative apparitions in cinema or TV before Disney's ''WesternAnimation/{{Dinosaur}}'' and ''Series/WalkingWithDinosaurs'' were broadcast during the [[TurnOfTheMillennium 20th-21st century change]]. The most recent one is in 2022's ''[[Film/JurassicWorldDominion Jurassic World Dominion]]''. RuleOfCool easily explains why: with its generic look and weak weapons, it doesn't bear comparison with ''UsefulNotes/TyrannosaurusRex'' jaws, ''[[TemperCeratops Triceratops]]'' horns, ''[[ToughArmoredDinosaur Stegosaurus]]'' plates, "[[RaptorAttack raptor]]" claws, or the immense size of [[GentleGiantSauropod sauropods]] -- and some portraits could even leave the beak or the thumbspikes substituting them with a lizard-head and generic hands, making it even more inconspicuous. However, its historical and scientific importance won't ever be deleted in dino-fans' consciousness, as no other dinosaur has run the whole two centuries of popular portraits: from [[https://nixillustration.com/science-illustration/2022/retro-vs-modern-02-iguanodon/ Crystal Palace rhinos, to giant two-legged iguanas, up to Disneyan horses]].

# '''TropeMaker:''' Crystal Palace Park

This dinosaur has appeared in almost every dino-film, but usually in minor roles -- basically with the sole purpose of increasing the variety of the "dinosaur world". And don't expect to hear its name, either -- even though it's not one of the shortest dino-names, it remains cool-sounding anyway. A good example is in the ''Franchise/JurassicPark'' films. Some ''Parasaurolophus''es are visible behind the ''Brachiosaurus'' in the famous "Welcome to Jurassic Park!" scene of the first film; they are also seen in every following sequel, too. But all these were simple cameos, and the animal is never named. (One character does make an attempt in the 2nd movie, but gives up fairly quickly.) Other unnamed appearances are in Disney movies -- ''WesternAnimation/{{Fantasia}}'' (where they have the old upright pose and a huge flap of skin between the crest and the neck) and ''WesternAnimation/{{Dinosaur}}'' (where are more modern-looking). One rare example of a major-character ''Parasaurolophus'' is seen in ''WesternAnimation/TheLandBeforeTime''... at least, Ducky and her parents are officially labeled as such: they're actually based on its distant relative ''Saurolophus''.

That said, ''Edmontosaurus'' hasn't gone an especially long way in non-docu media: when ''Edmontosaurus'' appears, it's simply known as a "duckbill," and the crested ''Parasaurolophus'' has become the most portrayed hadrosaur in fiction today (probably because of the crest and the less convoluted backstory). ''Edmontosaurus/Anatosaurus annectens'' is also ''much'' more common in documentaries than ''Edmontosaurus regalis'', and for good reason: With the possible exception of ''Hypacrosaurus'' (see below), ''E./A. annectens'' is the only hadrosaur known from the same time and place as ''Tyrannosaurus'', ''Triceratops'', and the other famous dinosaurs from the end of the Cretaceous. Therefore, if a work is showing the end of the Cretaceous and wants to be accurate, this is usually the hadrosaur they'll use.''E. regalis'' tends to show up much more in popular dino-books by contrast. Additionally, the unnamed Alaskan ''Edmontosaurus'' we briefly brought up at the start has shown up in the ''Film/WalkingWithDinosaurs'' movie and ''WesternAnimation/MarchOfTheDinosaurs'', albeit mostly identified with ''E. regalis''.

Even after it was established that hadrosaurs were mainly terrestrial, scientists still said they were more skilled swimmers than most other dinosaurs and would flee into the water to escape the less able giant theropods. Later research seems to indicate that hadrosaurs were no more accomplished swimmers than any other dinosaurs were, and that tyrannosaurs were probably just as capable of swimming as any other land animal was (ostriches can swim pretty well, and they don't have arms for paddling). Really, a lot of the bias regarding hadrosaurs as being exceptional swimmers or semi-aquatic has to do with the fact they are nicknamed "duckbills", naturally leading many to think think of them in comparison to modern-day waterfowl.

Even though has been extremely common in dino-books and other non-fictional media, ''Iguanodon'' did not make any significative apparitions in cinema or TV before Disney's ''WesternAnimation/{{Dinosaur}}'' and ''Series/WalkingWithDinosaurs'' were broadcast during the [[TurnOfTheMillennium 20th-21st century change]]. The most recent one is in 2022's ''[[Film/JurassicWorldDominion Jurassic World Dominion]]''. RuleOfCool easily explains why: with its generic look and weak weapons, it doesn't bear comparison with ''UsefulNotes/TyrannosaurusRex'' jaws, ''[[TemperCeratops Triceratops]]'' horns, ''[[ToughArmoredDinosaur Stegosaurus]]'' plates, "[[RaptorAttack raptor]]" claws, or the immense size of [[GentleGiantSauropod sauropods]] -- and some portraits could even leave the beak or the thumbspikes substituting them with a lizard-head and generic hands, making it even more inconspicuous. However, its historical and scientific importance won't ever be deleted in dino-fans' consciousness, as no other dinosaur has run the whole two centuries of popular portraits: from [[https://nixillustration.com/science-illustration/2022/retro-vs-modern-02-iguanodon/ Crystal Palace rhinos, to giant two-legged iguanas, up to Disneyan horses]].

The TurnOfTheMillennium saw a sudden increase in ''Pachyrhinosaurus'' appearances in pop culture, starting as a background character in Disney's ''WesternAnimation/{{Dinosaur}}'', then as a major character in the eighth ''WesternAnimation/TheLandBeforeTime'' film, and then as the lead role in the ''Film/WalkingWithDinosaurs'' film. It was, at one time, planned to appear in ''Film/JurassicWorldFallenKingdom'', but was replaced with the much more obscure ''[[UsefulNotes/PrehistoricLifeCeratopsids Sinoceratops]]''. ''Series/PrehistoricPlanet'' prominently features a herd of bristly ''Pachyrhinosaurus'' being menaced by a trio of ''Nanuqsaurus'' in the midst of a huge blizzard. It seems its oddness among the "classic" ceratopsids has contributed to this formerly unexpected success. Some part of its prominence can also be contributed to specimens being found in Arctic fossil deposits, leading some to imagine it as the dinosaur equivalent of the woolly mammoth or woolly rhino, complete with a speculative coat of insulating down.

Discovered by a French expedition to Niger led by Philippe Taquet in the 1970s, ''Ouranosaurus [[ExactlyWhatItSaysOnTheTin nigeriensis]]'' lived in what is today the Sahara Desert, just like ''Spinosaurus aegyptiacus'' (which was found a bit further north, ex. [[ExactlyWhatItSaysOnTheTin in Egypt]] and Morocco). Some thought the two animals' dorsal crests were a common adaptation for an arid environment, acting as solar panels or radiators like what is often thought for the plates of stegosaurians or the frill of ceratopsians, but like the latter cases, this is unproven. Additionally, we need to consider the fact when these dinosaurs were alive, the Sahara was a lush wetland, with ''Spinosaurus'' being an amphibious fish-eating dinosaur. Like ''Spinosaurus'', some scientists argue that ''Ouranosaurus'' had a fleshy and/or fatty hump instead of a “sail”, because its vertebrae are similar to those of modern bison. But others say that comparing dinosaurs with modern big mammals is not correct, since these are two completely distinct zoological groups. Until we don't found remains of soft tissues of both dinos, the question will remain unanswered. Interestingly, because of the scarcity of its fossil record (only two individuals were found in the expedition, and nothing more since) some think ''Ouranosaurus'' was more solitary than other ornithopods, averting SocialOrnithopod.

In 2021 ''Ouranosaurus'' has made its way into fiction, appearing in the third season of ''WesternAnimation/JurassicWorldCampCretaceous''. Here, they are presented as dangerous herd animals, almost like "duck-billed spinosaurs". Before, it is spottable in one of the many sequels to ''WesternAnimation/TheLandBeforeTime'' (''The Great Longneck Migration''), recognizable thanks to its "sail".

About the same size as ''Camptosaurus'', ''Ouranosaurus'' or ''Tenontosaurus'', the muttaburrasaur was visually distinct from all of them, thanks to its defining trait, an evident bulged nose reminiscent of the old portraits of the hadrosaur ''Kritosaurus''. This "big nose" is an unusually specialized trait for a basal iguanodontian like this, making its head more similar externally to that of a Late Cretaceous hadrosaurid than to a camptosaur or tenontosaur. No fossil hands are known from ''Muttaburrasaurus'', but it is typically represented with well-developed thumb-spikes in drawings -- even though their presence is impossible due to its primitiveness. Among the ornithopods we've covered here so far, only ''Tenontosaurus'' is considered more primitive than ''Muttaburrasaurus''; even ''Dryosaurus' is considered more derived despite it living long before the ''Muttaburrasaurus'' or the ''Tenontosaurus'' did. Thus, ''Muttaburrasaurus'' is considered a late-surviving basal animal, like ''Leaellynasaura'', ''Minmi'', and the giant amphibian ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Koolasuchus]]''. It seems Australian, Antarctic, and (in part) South American fauna remained primitive across the Mesozoic, perhaps until the Great Extinction of 66 mya. Even today, the mammalian fauna of Australia and (in part) of South America is rather peculiar compared with the other continents, while Antarctica has lost it completely when it froze, during the Mammal Age, aka the Cenozoic. This can be attributed to the isolation these continents experienced for much for the Mesozoic and Cenozoic -- something that continues today for Australia's marsupials and monotremes.

''Styracosaurus''' frill spikes were ''not'' true horns as commonly said, but only an exaggerated version of those protuberances commonly seen in ceratopsid species. Even though the most common portrayal has six spikes, it seems most specimens had only ''four''. But don’t rule out seeing styracosaurs with eight spikes (like in Disney's ''WesternAnimation/{{Dinosaur}}'') or more in popular works, or even with no frill and the spikes protruding directly from the back of the neck like the horned lizard of the deserts of North America. Interestingly, another modern species of lizard, the Jackson's chamaeleon of Africa, has three horns and a frill very reminiscent of ''Triceratops'', and the cowl of the Australian frilled lizard kinda resembles a ''Triceratops''' shield when open.

''Pachycephalosaurus wyomingensis'', the only known species (possibly; see below), owes its name to Wyoming. This dinosaur is distinguished by its dome-like head, which makes it look very [[MyBrainIsBig intelligent]]. However, the height of the dome was almost entirely made of almost one-foot-thick bone, and its brain wasn't larger than other dinosaurs', making its nickname "The Boneheaded Dino" quite accurate. A number of bony knobs and blunt spikes around the base of the dome and on its nose contrast with the smoothness of the dome to create a look of partial baldness or a monk's tonsure, i.e. a "Roman tonsure"; hence the epithet "[[RobinHood Friar Tuck]]-osaurus" in ''Film/TheLostWorldJurassicPark'' film. These knobs and spikes were homologous to those on the head and frill of the ceratopsians.

Juvenile pachyrhinosaurs did have a typical ceratopsid nose horn that was absorbed into the skull as they grew. This detail, along with its great size, massive limbs and other elements, firmly demonstrates that this animal is a true ceratopsid, more precisely a centrosaurine. ''Pachyrhinosaurus'' was both the largest and the last of the centrosaurines, going extinct 68 million years ago, at the same time its distant relative ''Triceratops'' first appeared. However, it's unlikely the two could have met, because because ''Pachyrhinosaurus'' lived much farther north--far north enough to experience snow in the winter, in fact!. The biggest species of pachyrhino (''P. canadensis'') was larger than the other species of its ceratopsid subfamily, but didn't reach the size of a ''Triceratops'' or a ''Torosaurus''.

That said, ''Edmontosaurus'' hasn’t gone an especially long way in non-docu media: when ''Edmontosaurus'' appears, it's simply known as a "duckbill," and the crested ''Parasaurolophus'' has become the most portrayed hadrosaur in fiction today (probably because of the crest and the less convoluted backstory). ''Edmontosaurus/Anatosaurus annectens'' is also ''much'' more common in documentaries than ''Edmontosaurus regalis'', and for good reason: ''E./A. annectens'' is the only hadrosaur known from the same time and place as ''Tyrannosaurus'', ''Triceratops'', and the other famous dinosaurs from the end of the Cretaceous. ''E. regalis'' tends to show up much more in popular dino-books by contrast. Additionally, the unnamed Alaskan ''Edmontosaurus'' we briefly brought up at the start has shown up in the ''Film/WalkingWithDinosaurs'' movie and ''WesternAnimation/MarchOfTheDinosaurs'', albeit mostly identified with ''E. regalis''.

Late Cretaceous North America has several examples of dinosaurs that were very common in older popular dino-books but now have been "substituted" in their role by close relatives. The carnivorous ''Gorgosaurus'' was synonymized with ''Albertosaurus'' between the 1970s and the 2000s, though this has been reversed, and it is now a valid genus again; the hadrosaur ''Kritosaurus'' was revealed to be based upon the related ''Gryposaurus'' in the 1990s (although it is still a valid genus); the ceratopsid ''Monoclonius'' is today thought by several experts as a non-diagnostic juvenile centrosaur; and the small deinonychosaur ''Stenonychosaurus'' was synonymized with ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Troodon]]'' since the 1980s but now it has again resurrected (with ''Troodon'' being rendered dubious). All this to not mentioning the notorious ''Trachodon''/''Edmontosaurus''/''Anatosaurus''/''Anatotitan'' case. The original specimen of ''Euoplocephalus'' was discovered in 1902, but between 1923 and 1929, three other genera very similar to it (''[[UsefulNotes/PrehistoricLifeAnkylosaurs Dyoplosaurus]]'', ''Scolosaurus'', and ''[[http://en.wikipedia.org/wiki/Anodontosaurus Anodontosaurus]]'') were named. All these three were combined into ''Euoplocephalus'' in 1971, but were rescued from the Invalid Box between 2007 and 2013 after showing that some patterns of armor were useful in classifying their owners.[[note]]For example, the ''Dyoplosaurus'' club was different from that of ''Euoplocephalus'', being longer than wide, while the ''Anodontosaurus'' club had pointed ends like a giant pickaxe. ''Dyoplosaurus'' was also older than most ''Euoplocephalus'' specimens, while ''Anodontosaurus'' lived after the latter but before ''Ankylosaurus''.[[/note]]

Several old books and models have portrayed the resulting "stegosaur-tailed ankylosaur", wrongly showing it with much more generic armor than the RealLife fossil. They usually named it correctly "Scolosaurus", but sometimes "Euoplocephalus" or even "Ankylosaurus": the ur-example is the picture by Zdenek Burian which shows this critter defending itself against a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Gorgosaurus]]''. Though few noticed, even [[WesternAnimation/TheLandBeforeTime one very popular work]] has made the same mistake: if observed carefully, the wise "Euoplocephalus" Rooter of the original film has armor analogous to Burian's picture, and also shows the pair of spikes on the tip of its tail when he goes away, revealing he's actually based on ''Scolosaurus''.

''Hypacrosaurus'' was, notably, the last of the lambeosaurines to live in North America, with its most recent fossils dating back to the time just before ''T. rex'' and ''Triceratops'' showed upon the scene. So while it probably wasn't around to be hunted by the rex, it did coexist with dinosaurs like ''Anchiceratops'', ''Arrhinoceratops'', ''Pachyrhinosaurus'', (see the ceratopsians folder above) and the previously mentioned ''Edmontosaurus regalis'' and ''Saurolophus'' -- all preyed upon by ''Albertosaurus''. In the nineties, a nidification site in North America full of ''Hypacrosaurus'' nests and hatchlings has been discovered, analogue to the classic ''Maiasaura''; this find has made ''Hypacrosaurus'' a much more well-understood duckbill among scientists.

Juvenile pachyrhinosaurs did have a typical ceratopsid nose horn that was absorbed into the skull as they grew. This detail, along with its great size, massive limbs and other elements, firmly demonstrates that this animal is a true ceratopsid, more precisely a centrosaurine. ''Pachyrhinosaurus'' was both the largest and the last of the centrosaurines, living just 1-2 million years before its distant relative ''Triceratops'', but much farther north (far north enough to experience snow in the winter, in fact!). The biggest species of pachyrhino (''P. canadensis'') was larger than the other species of its ceratopsid subfamily, but didn't reach the size of a ''Triceratops'' or a ''Torosaurus''.

The several ''Stegosaurus'' species ranged from 24 ft/7.5 m up to 30 ft/9 m long, and weighed from 1.5 up to 5 metric tons. The two most known have been ''S. stenops'' (stenops = "narrow face") and ''S. ungulatus'' (ungulatus = "the hoofed one"). Its plates and deep body made it look bigger than it was when seen from the side: actually, the stegosaur’s body was laterally flattened, and not as heavy as it seems. Its limbs were pillar-like; the front legs were much shorter than the hind legs, and the neck was set low above the ground (but not the degree seen in old portraits). Despite its overall size, ''Stegosaurus'' had a remarkably small head, with room for only 2.8 oz/80 g of brain: often stated as "walnut-sized", but actually it was larger than a walnut, closer to an apple in size. This has made it the most iconic dinosaur within the DumbDinos trope, though sauropods, also with small brains, are not far away. The small brain does ''not'' mean that stegosaurs and sauropods were witless, though. And they ''didn't'' have a secondary brain in their hip region as is often stated; the extra space there probably accommodated the nerves for the hindquarters, hindlegs and tail, and/or was partially occupied by fat or connective tissue. Not mentioning that this extra space in the sacrum is present also in modern reptiles/birds (except for the legless ones, like snakes) for these purposes.

Living 68 to 66 million years ago in Late Cretaceous North America, ''Triceratops'' was one of the last discoveries from the Bone Wars: its original find, an isolated horn-core, was first believed to be from a bison, despite bison living in the Cenozoic (the dating of rocks was still inaccurate at the time). Its name means "three-horned face" after its most prominent feature. It was about 26-30 ft/7-9 m long and weighed about 5-9 metric tons, and was one of the biggest ornithischian dinosaurs (only some hadrosaurs were larger). Hundreds of skulls are known, but amazingly not a complete skeleton. The biggest known ''Triceratops'' specimen is known with the nickname [[http://en.wikipedia.org/wiki/Big_John_(dinosaur) Big John]].

''Styracosaurus albertensis'' ("Alberta's thorny lizard") lived in North America 75 million years ago, slightly earlier than ''Triceratops''. It was discovered in 1913 during the second great North American "dino-rush". Most North American Cretaceous dinosaurs were actually described during this "rush", but only the coolest-looking ones joined the stock dinosaur ensemble. About half as long as ''Triceratops'', only 18 ft/5.5 m and weighing nearly 3 tons, the styracosaur was actually even more rhino-like. It had much longer horn above the nose but only hints of horns above its eyes. It had a round, short frill, but with several pairs of long spikes protruding from the top in a rayed manner, and shorter protuberances on the anterior edge. This sort of horned hairdo incidentally makes its head resemble the ''Statue of Liberty'' (built completed 1886, well before its discovery). ''Styracosaurus'' had also shorter and stronger jaws than ''Triceratops''. Based on huge bonebeds containing hundreds of individuals, some speculate it was more sociable than ''Triceratops''es and lived in larger herds.

''Protoceratops'' lived 75—71 million years ago in Late Cretaceous Asia, unlike the giant ceratopsids, which were almost exclusively North American in distribution (the Chinese ''Sinoceratops'' being the sole exception). It was around 6 ft/1.8 m in length and weighed no more than 400 lbs/180 kg. Protoceratopsids are generally smaller and more primitive than ceratopsids, and were once considered the ancestors of the latter group: hence the name, meaning "first horned face".

''Pachycephalosaurus'' (pronounced "pAcky-sEfalo-[=SAURus=]"; "-kEfalo-" is OK too) means "thick-headed lizard", and is by far the biggest known pachycephalosaur, but it's still small compared to most stock ornithischian dinosaurs. Its actual length is uncertain: popular books often set its size at up to 30 ft/9 m, but a length of 15-18 ft/4.6-5.5 m is more likely. All of its relatives were no longer than 10 ft. Described in 1931 from a single skull, it was initially identified as ''Troodon'' because the ''Troodon'' was at the time known only from one tooth, which is similar to some pachycephalosaur teeth, and was renamed ''Pachycephalosaurus'' only in 1943. No other parts of the body have been found since then: reconstructions are typically based on smaller pachycephalosaurians, especially ''Stegoceras'', the most complete pachy to date.

25-30 ft/8-10 m long and weighing 4-5 metric tons, roughly as much as an elephant, ''Parasaurolophus'' was a typical hadrosaur, with longer and stronger hindlimbs than forelimbs, three-toed feet ending in blunt nails, a long powerful tail not ending in a whip-like shape, a small "hump" on its shoulders, a short but flexible neck with many short vertebrae like a bird (unlike the long but rigid neck of sauropods), and the classic "duck-billed" head, although the "bill" was not as flat and wide as in other relatives. It lived 76 to 73 million years ago in Late Cretaceous North America. . Its long, backwards-pointing protrusion made its skull a bit longer than an adult human’s height. Even though it is often called a "horn", it was actually an extension of the nasal cavities, and ended in a blunt point. Of course, you can often expect to see "paras" in media with the crest looking like a literal horn. Its striking crest makes ''Parasaurolophus'' one of the most popular hadrosaurs, if ''the'' most popular. Significantly, ''Parasaurolophus''[='=] remains are rarer than other duckbills. There are usually three species recognized: ''P. walkeri'' (the classic one), ''P. tubicen'' (tubicen = trumpet player), and ''P. cyrtocristatus'' (meaning "short-crested"). ''P. tubicen'' is the largest of the three and ''P. cyrtocristatus'' has both the smallest body size and smallest crest of the bunch, with both being found in Utah and New Mexico. ''P. walkeri'' was almost identical to ''P. tubicen'', except it lived in Alberta, was a tad smaller, and had longer, more slender crest.

Some decades later the discovery of the first ankylosaurian in England, a companion was added: ''Polacanthus foxii''. English too (some dubious remains from the USA were once also attributed to its genus), and conviving with ''Iguanodon'' and ''Hypsilophodon'' in the Early Cretaceous, ''Polacanthus'' was rather small compared to ''Ankylosaurus'' or ''Euoplocephalus'' being 4 m/16 ft long, and the first remains found in the Isle of Wight were very incomplete. This explains why in older depictions ''Polacanthus'' had very light armor, consisting only of pairs of long dorsal spikes (hence the name, [[ExactlyWhatItSaysOnTheTin "many spines"]]), a bony shield on its hips, and pairs of small triangular plates on the tail. This kind of armor is typical for the polacanthines, the subgroup of ankies which it's the archetype of. But some portrayals took it a further step, and gave it a stegosaur-like thagomizer, or a small ankylosaurid club. The spiked-tailed polacanth made cameo appearances in ''Film/PlanetOfTheDinosaurs'' and the film adaptation of ''Film/TheLandThatTimeForgot''. The animal has also a more prominent role in the puppet series ''Series/{{Dinosaurs}}'' as Robbie Sinclair's friend Spike, homonymous with the ''Stegosaurus'' non-talking puppy of ''WesternAnimation/TheLandBeforeTime'' franchise.

''Edmontosaurus'' is one of the most scientifically known dinosaurs, with more than ''10,000'' known specimens (most other dinosaurs have less than 100 known specimens, but usually much fewer) showing every detail about its life, even diseases like cancer or fractures. The most striking ones are the "petrified mummies" (all of ''E./A. annectens''), which have preserved not only skin prints, but also ''hardened muscles''. If you don't believe us, [[http://en.wikipedia.org/wiki/Trachodon_mummy see]] [[https://en.wikipedia.org/wiki/Edmontosaurus_mummy_SMF_R_4036 them]] [[http://en.wikipedia.org/wiki/Dakota_(fossil) here]]. The third find shows an unexpected thing: hadrosaurs had a much more massive tail than traditionally thought. If this’d be true for all dinosaurs, then [[ScienceMarchesOn many classic studies about dinosaur biomechanics should be reviewed]]. For example, hadrosaurs and their kin are often thought mainly quadrupedal, but a heavier tail would make their center of gravity just under their hips, perfectly balancing their body on two legs. Maybe hadrosaurs mainly walked on two feet and walked on all fours only when grazing, drinking or resting, like kangaroos -- a possible proof of this is that most hadrosaur and iguanodont tracks seemingly do not show prints of forelimbs. Interestingly, Mummy #3 also tells us hadrosaurs were much faster than previously thought, up to speeds of 45 km/hr.

Discovered in the 1970s, ''Shantungosaurus giganteus'' ("gigantic Shandong lizard", from the Chinese province it was first found) was quite similar to ''Edmontosaurus'', and usually believed closely related with it. However, it was bigger than the latter, the same size of the aforementioned "giant lambeosaur" ''Magnapaulia'' (15 m/50 ft long and 12 tons or more in weight). Despite the fact they rivalled certain sauropods in size, neither hadrosaur has received any attention in fiction yet, although they are staples of dino-books. Both subfamilies of duckbills, the lambeosaurines and saurolophines, have members both in Asia and in North-America -- giving more proof of a connection between the two landmasses in the Late Cretaceous by the today-Bering Strait.

The most known ''Camptosaurus'' species is ''Camptosaurus dispar''; other alleged ''Camptosaurus''es found in Europe (Portugal and England) have been given their own genera, like ''Draconyx'' and ''Callovosaurus''. It could have fallen prey to ''Ceratosaurus'' and ''Allosaurus'': but a fully-grown, 7 m/20 ft long ''Camptosaurus'', the same length of a 1-ton ''Ceratosaurus'' but heavier than it, 2 tons, could have defended itself against it like a wildebeest or a zebra can against predators smaller than a lion.

Here’s one of the most classically-cited dinosaurian MixAndMatchCritter examples: ''Ouranosaurus'', "brave monitor-lizard" ("ourane" is both the Arabic word for "brave" and the Tuareg name for the Desert Monitor). This medium-sized (7 m/20 ft long) ornithopod looked like a cross between other more familiar dinosaurs. It had a flat duck-like bill like ''Edmontosaurus''; a small relief on its head like ''Maiasaura''; thumb spikes like ''Iguanodon''; and, most strikingly, a wide spinal crest on its back, similar to ''Spinosaurus'' but less tall and extending from the shoulders down to the tip of the tail. Like the spinosaur, this dorsal crest has traditionally been depicted as a [[UsefulNotes/StockDinosaursNonDinosaurs Dimetrodon]]-like "sail" in popular portraits. The combination of duck-like bill and thumb spikes is explained by the fact that ''Ouranosaurus'' was a sort of in-between of hadrosaurs and ankylopollexian iguanodontians, more derived than ''Iguanodon'' and ''Camptosaurus'' but less so than ''Edmontosaurus'' and ''Parasaurolophus''. Think of it as among the most derived of the iguandontians.

The "hetero" lived in the Early Jurassic like the armored ''Scelidosaurus'' but farther south, in South Africa, 200-190 million years ago. ''Heterodontosaurus'' superficially resembled ''Hypsilophodon'' with its slender, bipedal body, but was even smaller (1.20 m/4 ft long), more robust, and with longer forelimbs. As the namesake and archetype of the [[https://en.wikipedia.org/wiki/Heterodontosauridae heterodontosaurids]], it was actually one of the "largest" basal ornithischians, despite being only a bit bigger than a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Compsognathus]]''. Its skeletons have not left traces of feather-like structures, but since its close relative ''[[UsefulNotes/PrehistoricLifePrimitiveOrnithischians Tianyulong]]'' had them, it's highly probable that ''Heterodontosaurus'' also had them.

Merely 90 cm/3 ft long, even smaller than the already-small ''Heterodontosaurus'', and with a more gracile frame, a smaller head, and shorter forelimbs, ''Lesothosaurus'' was about the bulk of a ''Compsognathus'' weighing only 3-4 kg. Unlike the scelidosaurians and the heterodontosaurians, it doesn't seem to have any specialization in its anatomy. Its mouth had simple teeth not apt for proper grinding but only for tearing vegetation just like the contemporaneous prosauropods. It probably had only small "cheeks", but already had the lower toothless bill (technically, the "predental bone") that is the main hallmark of every ornithischian other than the shape of the pelvic bones. Its forelimbs were short and five-digited; its hindlimbs four-digited, birdlike and apt for running; and its tail long and flexible (like ''Heterodontosaurus'', its vertebrae lacked the bony tendons of the more evolved bird-hipped dinos). Finally, its pelvis lacked a "prepubis", the forward-pointing prominence of the pubis typical of most evolved ornithischian lineages (the scelidosaurs and heterodontosaurs also lacked it).

The [[http://en.wikipedia.org/wiki/Ornithopod Ornithopod]] group contains several ornithischian dinosaurs of different size, from the Middle Jurassic to the Late Cretaceous. The smallest ones were slender, completely bipedal, and possibly omnivorous. The more evolved ones became bigger and returned to partial quadrupedality, as well as becoming strict herbivores. The largest were among the most massive non-sauropod dinosaurs. "Ornithopod" means "bird-foot": they had limbs and feet similar to but (ironically) less bird-like than those of the theropods. Unlike the latter, they had small mouth openings and blunt teeth for grinding plant matter. Ornithopods are the most abundant dinosaurs in the fossil record, and as such [[SocialOrnithopod are often portrayed as inoffensive herd-living animals akin to deer and antelope]]. Rven though they lacked the thick defenses of the armored ornithischians mentioned above, they made up for that with either speed or sheer bulk.

The discovery of ''Muttaburrasaurus'', ''Minmi'', and ''Leaellynasaura'' in the 1980s made sensation in Australia, because very few dinosaurs were known before in the LandDownUnder, all fragmentary. ''Muttaburrasaurus'' still is one of the most complete dinosaurs found there; ''Leaellynasaura'' ‘s skeletons are more incomplete, but the latter's importance was due to having contributed to enforce the “warm-blooded dinosaurs” hypothesis even more. In the Early Cretaceous, Australia was not the temperate/tropical/desertic country we know today, but a colder world with warm summers and cold winters, because it was much closer to the South Pole. How could such a small, clearly non-migratory animal like this manage to survive that icy winter? The only explanation was that ''Leaellynasaura'' was warm-blooded. Furthermore, its unusually big eyes could have been used to see throughout the darkness of the polar winter. All these arguments were discussed in ''Series/WalkingWithDinosaurs'', in which a family of ''Leaellynasaura'' are the main characters. The show also portrayed ''Muttaburrasaurus'', as a migrating animal that flees the winter in herd like caribou. And in the years since that show, fossils demonstrating that many small ornithischians possessed feathers have led many to depict ''Leaellynasaura'' with a thick coat of fluff to shield it from the winter.

Among basal Ornithischian dinosaurs, there were curious things. ''Heterodontosaurus tucki'', for example, might be renamed the [[MixAndMatchCritter boar-bird]].

The "hetero" lived in Early Jurassic like the armored ''Scelidosaurus'' but farther south, in South Africa, 190 million years ago. ''Heterodontosaurus'' superficially resembled the ornithopod ''Hypsilophodon'' with its slender, bipedal body, but was even smaller (1.20 m/4 ft long), more robust and with longer forelimbs. It was actually one of the "largest" basal ornithischians, despite being only a bit bigger than a ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Compsognathus]]''. Its skeletons have not left tracks of feather-like structures around them, but since its close relative ''[[UsefulNotes/PrehistoricLifePrimitiveOrnithischians Tianyulong]]'' had surely them, it's highly probable that ''Heterodontosaurus'' also had them.

Unlike the ur-tank dinosaur ''Scelidosaurus'', ''Heterodontosaurus'' was discovered only in TheSixties. Its name means “lizard with different teeth”, and with reason: no other dinosaur had such a diversified dentition, with ''three'' kinds of teeth surprisingly similar to those found in mammals. The most noticeable are two pairs of canine-like “fangs” visible when the mouth closed like a boar; behind, molar-like teeth to grind up tough vegetation analogue to the more evolved ornithischians; in front of them the small peg-like teeth only on the tip of the upper jaw, the typical condition of all basal bird-hipped dinos. This makes its head as an odd mix of primitive and evolved traits.

We are not sure about what the heterodontosaur ate in life, because of this specialized dentition. The dominant hypothesis is that ''Heterodontosaurus'' was a mostly herbivorous omnivore, eating insects other than vegetation, while the "fangs" could have been used not for alimentation but for display and/or competition, a bit like in male baboons or male musk-deer (thus acting more like "tusks"). Some scientists suspect only males did have the large canines like what is seen in some small species of deer like the musked one or the muntjac, or the mouse-deer, but there is no evidence. Other heterodontosaurids had different combinations of teeth: some species were devoid of "tusks", others had them only in their upper jaw, and still others had them only in the lower jaw.

''Heterodontosaurus'' has been a very common sight in popular informative dino-books as an example of an early basal ornithischian dinosaur, often preferred to other Triassic/Early Jurassic bird-hipped dinosaurs because of its [[RuleOfCool unusual, striking look]]. In these portrayals ''Heterodontosaurus tucki'' is often shown together with the two most-known early dinosaurs, ''Plateosaurus sp.'' and ''Coelophysis bauri'', and sometimes shown as the latter's prey. This could be accurate, as their relatives did live along it in southern Early Jurassic Africa at the time...but AnachronismStew and MisplacedWildlife are in play altogether, since ''Coelophysis'' lived only in Late Triassic North America, while the plateosaur was around in Late Triassic Europe. Some suspect that the heterodontosaur could have defended itself well against enemies thanks to its robust tusks like modern baboons and peccaries do with big cats, but this is not demonstrable due to the lack of fossilized combats like the one between ''Protoceratops'' and ''Velociraptor''.

When talking about Ornithischians, we can find the same issues of Saurischians: in the Triassic/Early Jurassic they were all so-similar each other, it’s hard task to classify them accurately. Nonetheless, they are extremely important animals for scientists, no matter their often-tiny size. Other than the scelidosaurians and the heterodontosaurians (which make two distinct groups on their own), we have several other examples, among them ''Lesothosaurus''.

''Lesothosaurus diagnosticus'' was once considered the [[{{Pun}} forerunner]] of all bird-hipped dinos, and thought not to belong to any great ornithischian group; [[ScienceMarchesOn recent research]] suggest it could be a very basal Thyreophoran, thus ancestor of Scelidosaurs, Stegosaurs, and Ankylosaurs. From Early Jurassic Southern Africa like ''Heterodontosaurus'', its name derives from [[ExactlyWhatItSaysOnTheTin the Kingdom of Lesotho]], a small South African enclave (once called Basutoland) where its remains were dug out in 1978; the species name ''diagnosticus'' underlines its importance to understand early ornithischians evolution. Fragmentary remains from Lesotho that have been named ''Fabrosaurus australis'' ("Southern Fabre's lizard") may be synonymous with it; since they were named slightly before ''Lesothosaurus'', in TheSixties, ''Fabrosaurus'' would be the valid genus name for this dinosaur. Other possible ''Lesothosaurus'' remains have been classified in 2005 in another genus, "Stormbergia" (probably a simple synonym name).

In old textbooks, the "fabrosaur" was often shown as the prototypical generic-looking basal ornithischian; since the 1980s, ''Lesothosaurus'' took over this role. Once, the "fabrosaurid" family was recognized by scientists as a catch-all grouping for undetermined small ornithischians from Triassic to Early Cretaceous, but modern cladistic science do not accept artificial assemblages like this, and "fabrosaurid" has mostly disappeared in literature. Alleged "fabrosaurids" included also some animals now considered ornithopods or near-ornithopods, like the Late Jurassic U.S. ''Nanosaurus'' (lit. "dwarf lizard", common in old books as an example of a small dinosaur).

Merely 90 cm/3 ft long, even smaller than the already-small ''Heterodontosaurus'', and with a more gracile frame with smaller head and forelimbs, ''Lesothosaurus'' was about the bulk of a ''Compsognathus'' weighing only 3-4 kg. Unlike the scelidosaurians and the heterodontosaurians, it seems not to have any specialization in its anatomy. Its mouth had simple teeth not apt for proper grinding but only to tear vegetation off to the plants just like the contemporaneous prosauropods; it probably had only small "cheeks", but had already the lower toothless bill (technically, the "predental bone") which is the main hallmark of every ornithischian other than the shape of the pelvic bones. Its forelimbs were short and five-digited, its hindlimbs four-digited, birdlike and apt for running, its tail long and flexible (like ''Heterodontosaurus'', its vertebrae lacked the bony tendons of the more evolved bird-hipped dinos) and it not shows signs of armor on its body. Finally, its pelvis lacked the "prepubis", a forward-pointing prominence of the pubis typical of all the main/most evolved ornithischian lineages (the scelidosaurs and heterodontosaurs also lacked it).

Because of the body-shape popular dino-books often give to it, it was said that ''Lesothosaurus'' "resembles a lizard more than any other dinosaur", but in other illustrations ''Lesothosaurus'' looks more like an undersized ''Hypsilophodon''. Interestingly, it's also hypothesized that ''Lesothosaurus'' underwent long "hibernations" to survive the harsh desertic conditions of the habitat it lived within, but this is not yet demonstrated.

About this dinosaur there are the same issues of ''Heterodontosaurus'' and ''Scelidosaurus'' in pop-portrayals: it can be shown living alongside ''Plateosaurus'' and ''Coelophysis'', despite being from Early Jurassic and not Triassic like the latter two. It can be shown as a coelophysis' prey -- given its size and lack of defenses outside running this could be possible if the two met in RealLife. Like ''Hypsilophodon'', ''Heterodontosaurus'' or the prosauropod ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Mussaurus]]'', ''Lesothosaurus'' can also be cited as an example of a particularly small herbivorous dinosaur.

''Scutellosaurus'' ("lizard with small shields", not to be confused with the near-reptile ''[[UsefulNotes/StockDinosaursNonDinosaurs Scutosaurus]]'') has traditionally been the most primitive thyreophoran, variably classified in the Scelidosaurids or in its own family, Scutellosaurids.

Discovered only in the 1980s, ''Scutellosaurus lawleri'' was also a small bipedal animal with a similar look, but slightly bigger, longer-tailed, more robustly-built than the lesothosaur, and with longer forelimbs: some think was partially quadruped. More importantly, it had a light armor made by small bony plates placed in rows upon its torso, and a row of plates along its backbone from neck to tail: all similar to the armor of the bigger ''Scelidosaurus'', but without the "horns" on its head. Some could say ''Scutellosaurus'' was a bit like a primitive miniature ''Tenontosaurus'' because of its very developed tail longer than the rest of the body from nose to hips (''Scelidosaurus'' had a more normally-long tail).

Like the scelidosaur, ''Scutellosaurus'' lived in Early Jurassic, but was found not in Europe like the former but in Arizona, where the popular double-crested ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Dilophosaurus]]'' and the small early land-living crocodile-relative ''[[UsefulNotes/PrehistoricLifeNonDinosaurianReptiles Protosuchus]]'' lived. Some portrayals have shown the scutellosaur as the dilophosaur's prey, but this is not confirmed. Despite its small size for dinosaur standards ''Scutellosaurus'' was slightly bigger and heavier than ''Protosuchus'', and the latter arguably hunted only young scutellosaurs. If the dinosaur had "feathers" or not, this is unknown: but if it had them, they were interspersed between the bony scutes that give to it its name.

There were many non-hadrosaur ornithopods as well, but only one of them has made significant appearances in fiction, ''Iguanodon'' (again, this is the biggest of the ensemble). If you are lucky, the much smaller ''Hypsilophodon'' may also show up, but it's almost never named. Both were from Early Cretaceous Europe. And if you're even luckier you might see the Late Jurassic ''Camptosaurus'', ''Dryosaurus'', and ''Nanosaurus'', the first similar to ''Iguanodon'' and the other two to ''Hypsilophodon''. Also worthy of note are ''Tenontosaurus'' and ''Ouranosaurus'' because are they are strongly associated with one famous predatory dinosaur each (''Deinonychus'' and ''Spinosaurus'' respectively; albeit for different reasons). ''Muttaburrasaurus'' and ''Leaellynasaura '' are known for being rare examples of Australian dinosaurs, while ''Thescelosaurus'' and ''Orodromeus'' are the animals that the controversial "petrified heart" and "petrified nests" were attributed to, respectively. ''Heterodontosaurus'', ''Lesothosaurus'', ''Fabrosaurus'', and ''Scutellosaurus'' are here for convenience, but are not true ornithopods anymore according to modern knowledge. ''Iguanodon'', ''Camptosaurus'', ''Dryosaurus'', ''Tenontosaurus'', ''Muttaburrasaurus'', and ''Ouranosaurus'' are all part of a group of ornithopods known as the iguanodontians, which include the ancestors of the hadrosaurs. Meanwhile, ''Hypsilophodon'', ''Leaellynasaura'', ''Orodromeus'', ''Thescelosaurus'' and tiny ''Nanosaurus'' once formed a group called the "hypsilophodonts", but are now considered to be a miscellany of extremely primitive ornithopods or even basal ornithschians and not true ornithopods at all.

''Gastonia'' has recently become popular in paleo-media, both because its armor was especially spiky and impenetrable among ankylosaurians, and because lived just alongside the famous "giant raptor" ''Utahraptor'' -- both dinosaurs were found in the same geological formation. ''Gastonia'' and ''Utahraptor'' have become [[AnimalJingoism stock enemies]] as they become better known, but its likely that in reality, ''Utahraptor'' would have preferred hunting the much less heavily defended mid-sized iguanodontians and basal therizinosauroids it also lived alongside.

Non-stock ankylosaurs and stegosaurs tend often to be ignored in visual media. Maybe their reputation of “slow and foolish” has done its part, even though [[ToughArmoredDinosaur this fame is undeserved]]. A good example of missed opportunity was a small ankylosaur discovered in Australia in 1980, with one of the least dinosaurian names one could imagine: ''Minmi'', aka "the shortest-named dinosaur" until the 2000s, when it was beaten by the small theropod ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods Mei]]'' and then the bat-winged theropod ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods Yi]]'' in 2015. There is a backstory however: ''Minmi'' comes from “Minmi Crossing”, the locality where its only skeleton was discovered. After a second presumed skeleton was found in the early nineties (reclassified as ''[[http://en.wikipedia.org/wiki/Kunbarrasaurus Kunbarrasaurus]]'' in TheNewTens), ''Minmi'' and this longer-named relative have since then become together the most complete Australian dinosaurs. And yet ankylosaurs do not appear in the ''Series/WalkingWithDinosaurs'' episode "Spirits of the Ice Forest" set in Early Cretaceous, in which ''Muttaburrasaurus'', ''Leaellynasaura'', and the “polar allosaur” appear, despite being all contemporaries.

''Psittacosaurus'' was discovered in the 1920s in Mongolia together with ''Protoceratops''. Its discoverer was famed paleontologist Roy Chapman Andrews. Since then, psittacosaurs have been discovered everywhere in eastern Asia, from Siberia to China to Thailand, but it was recognized as a basal ceratopsian only in the 1970s: it was believed an ornithopod before because of its body frame reminding a miniature short-tailed iguanodont. Its fossil record is extremely rich, on the same level of ''Protoceratops'' -- individuals of all ages are known, and also several nests full of eggs. Our “parrot-dinosaur” also detains the record of the non-avian dinosaur with the most species described: more than 10! The most classic one is ''P. mongoliensis'', "Mongolian parrot lizard".

There were many non-hadrosaur ornithopods as well, but only one of them has made significant appearances in fiction, ''Iguanodon'' (again, this is the biggest of the ensemble). If you are lucky, the much smaller ''Hypsilophodon'' may also show up, but it's almost never named. Both were from Early Cretaceous Europe. And if you're even luckier you might see the Late Jurassic ''Camptosaurus'', ''Dryosaurus'', and ''Nanosaurus'', the first similar to ''Iguanodon'' and the other two to ''Hypsilophodon''. Also worthy of note are ''Tenontosaurus'' and ''Ouranosaurus'' because are they are strongly associated with one famous predatory dinosaur each (''Deinonychus'' and ''Spinosaurus'' respectively; albeit for different reasons). ''Muttaburrasaurus'' and ''Leaellynasaura '' are known for being rare examples of Australian dinosaurs, while ''Thescelosaurus'' and ''Orodromeus'' are the animals that the controversial "petrified heart" and "petrified nests" were attributed to, respectively. ''Heterodontosaurus'', ''Lesothosaurus'', ''Fabrosaurus'', and ''Scutellosaurus'' are here for convenience, but are not true ornithopods anymore according to modern knowledge. But even ''Hypsilophodon'', ''Leaellynasaura'', ''Orodromeus'', ''Thescelosaurus'' and tiny ''Nanosaurus'' (once collectively known as "hypsilophodonts") have been put outside ornithopods proper by some scientists, being argued by them to have actually been "basal ornithischians".

Although nearly as big as ''Tyrannosaurus'' (10 m or more, and up to 4 tons), ''Iguanodon'' has not an especially striking look among Stock Dinosaurs. Being an earlier relative of hadrosaurs and possibly their ancestor, its shape resembled one of the latter, with three-toed hindfeet, a lexible neck (but less so than hadrosaurs), a long muscular tail stiffened by bony tendons, a massive body, and hindlimbs longer and stronger than forelimbs. Non-hadrosaurian traits include: the backbone not being curved at the shoulder level; grinding teeth much less numerous and put in one single row on each half-jaw like almost all non-hadrosaur dinosaurs; a totally crest-less, bump-less head; and a deep, narrow beak very unlike the duck-billed one.

''Camptosaurus'' ("bent lizard") was similar to ''Iguanodon'' above, but smaller (5-7 m long) and with mere hints of thumbspikes -- some portrayals show ''Camptosaurus'' totally spike-less or with fully-developed ''Iguanodon''-like spikes, both incorrect. It had the same bulky body, horse-like head, and general shape of ''Iguanodon'', but was probably more bipedal than the latter. It also preserved the ancestral forth digit in its feet, lost in ''Iguanodon'' and the hadrosaurs: indeed, ''Camptosaurus'' was one of the most primitive big ornithopods and one of the most basal thumb-spiked iguanodonts (properly known as [[http://en.wikipedia.org/wiki/Ankylopollexia ankylopollexians]], meaning "hooked thumbs"). In the Jurassic world still dominated by sauropods, camptosaurids and stegosaurians were the only big ornithischians that were successful, anticipating the great diversity bird-hipped dinosaurs reached later in the Cretaceous.

''Dryosaurus'' was smaller than ''Camptosaurus'' and much more slender, similar to a ''Hypsilophodon'' in shape being totally bipedal. Compared with ''Hypsilophodon'', the dryosaur was larger (3-4 m long), slightly more robust, with a shorter head, toothless upper beak other than the lower, and lacking the forth reversed toe of ''Hypsilophodon'' and (ironically) the closer-to-''Iguanodon'' ''Camptosaurus''. Like the camptosaur, ''Dryosaurus'' was actually a basal iguanodont and not related to ''Hypsilophodon'', and the prototype of its own lineage, the Dryosaurids. It was [[ScienceMarchesOn once]] considered a big "hypsilophodont", as big as the Late Cretaceous ''Thescelosaurus'', but "hypsoliphodont" is no longer considered an actual group, rather a motley collection of miscellaneous small ornithopods and basal ornithischians.

This was one of the most basal known iguanodontians, an Early Cretaceous animal similar in size to the more evolved but earlier ''Camptosaurus''. Unlike the latter, the tenontosaur was totally devoid of thumbspikes, being more basal than the ankylopollexian iguanodonts (just like ''Dryosaurus'' was). And also like the dryosaur, it was [[ScienceMarchesOn once considered]] an overgrown "hypsilophodont" -- more precisely, the biggest member of the group by far. It had long front limbs (classic portrayals often show it quadrupedal) with five digits each, a long neck, a small head, and the primitive four-fingered hindfeet of basal ornithopods, but its most distinctive trait was surely its tail. Its tail was much longer than in most other relatives, ''twice'' the length of the rest of its body, and often depicted as a sort of "whip", almost like the tail of a diplodocid sauropod -- but it could have actually been more rigid than often shown.

Rather similar to ''Dryosaurus'' in appearance, ''Thescelosaurus'' had previously been classified by some as a small basal iguanodont like ''Dryosaurus'' was, but cladistic research have revealed it instead belonged to its own lineage of dinosaurs. Rather robustly-built if compared with ''Hypsilophodon'', the thescelosaur had some small bony scutes on its back, maybe placed under the skin and not visible in the living animal. Once thought unique to this dinosaur, it has since been found that ''Hypsilophodon'' also possessed these osteoderms, which were arguably for defense.

Here’s one of the most classically-cited dinosaurian MixAndMatchCritter examples: ''Ouranosaurus'', "brave monitor-lizard". This medium sized (7 m/20 ft long) ornithopod looked like a cross between other more familiar dinosaurs. Flat duck-like bill like ''Edmontosaurus''; a small relief on its head like ''Maiasaura''; thumbspikes like ''Iguanodon''; and, more strikingly, a wide spinal crest on its back, similar to ''Spinosaurus'' but less tall and extending from the shoulders down to the tip of the tail. Like the spinosaur, this dorsal crest has traditionally been depicted as a [[UsefulNotes/StockDinosaursNonDinosaurs Dimetrodon]]-like "sail" in popular portraits. The duck-like bill is explained by the fact that ''Ouranosaurus'' was a strict hadrosaur relative, but still not one.

Discovered by a French expedition in Niger led by Philippe Taquet in the 1970s, ''Ouranosaurus [[ExactlyWhatItSaysOnTheTin nigeriensis]]'' (the only known species) was once considered an evolved hadrosaur-like Iguanodontid, was smaller than ''Iguanodon'' and lived further south than it, in Cretaceous Sahara, just like ''Spinosaurus aegyptiacus'' (which was found a bit more northernly, ex. [[ExactlyWhatItSaysOnTheTin in Egypt]] and Morocco). Some thought the two animals' dorsal crests were a common adaptation for an arid environment, acting as solar panels or radiators like what is often thought for the plates of stegosaurians or the frill of ceratopsians, but like the latter cases, this is unproven. Because of the scarcity of fossil record (only two individuals were found in the expedition) some think ''Ouranosaurus'' was more solitary than other ornithopods, averting SocialOrnithopod.

In popular works the spinosaur has often been shown as the [[RedShirt predator of the ouranosaur]], the latter being smaller and thus a potentially easy prey for it; but [[AnachronismStew this is actually a mistake]], simply because ''Ouranosaurus'' lived 15 million years before ''Spinosaurus'' (always in the Cretaceous, though). Just as an example, the ''Ouranosaurus'' one documentary appearance in Series/PlanetDinosaur showed the two living at the same time. Here, ouranosaurs appear as herd animals, but as said above, there is no proof of this. Even today, not all deer/antelope species are gregarious like gnus or zebras -- for examples, moose and kudus are known to be rather lonely animals.

Like ''Spinosaurus'', today some scientists argue that ''Ouranosaurus'' had a fleshy and/or fatty hump instead of a “sail”, because its vertebrae are similar to those of modern bison. But others say that comparing dinosaurs with modern big mammals is not correct, since these are two completely distinct zoological groups. Until we don't found remains of soft tissues of both dinos, the question will remain unanswered.

In 2021 ''Ouranosaurus'' has made its way in fiction, in the third season of the animated TV series ''WesternAnimation/JurassicWorldCampCretaceous''. Here they are presented as dangerous herd animals, almost like "duck-billed spinosaurs". Before, it is spottable in one of the sequels of the ''Land Before Time'' movie ("The Great Longneck Migration"), recognizable thanks to its "sail".

If you’ve seen the fifth episode of ''Walking With Dinosaurs'', you’ll already have the idea what we’re talking about. Many other dinosaurs are known today from Africa, from huge ''Giraffatitan'' & ''Carcharodontosaurus'' to smallish ''Massospondylus'' (the most abundant) & ''Kentrosaurus'', to the tiny ornithischians ''Heterodontosaurus'' & ''Lesothosaurus'' (see below for these two). But very few non-bird dinosaurs are known from Australia, even today. Some important dino-fossils were found there in TheEighties, especially four animals: ''Muttaburrasaurus langdoni'', ''Minmi paravertebra'' (an ankylosaur), ''Leaellynasaura amicagraphica'' (a basal ornithischian), and "Allosaurus australis" (an alleged dwarf allosaur species), all from Early Cretaceous East Australia. ''Muttaburrasaurus'' is probably the most well-known and portrayed dinosaur of Australia in media. Like many Australian fossils has a rather odd-sounding name, but this is justified: it comes from Muttaburra, a small village of the Queensland outback. It looked like an undersized ''Iguanodon'', but was only apparently a strict relative: it was more primitive despite having lived slightly more recently (100 mya). It had different grinding teeth, and primitive four toes for each foot like camptosaurs: it was indeed believed once a camptosaurid.

About the same size of ''Camptosaurus'', ''Ouranosaurus'' or ''Tenontosaurus'', the muttaburrasaur was visually distinct from all them by its evident bulged nose, its defining trait, reminiscent of the old portraits of the hadrosaur ''Kritosaurus'' and to the skull of other big ornithopods. This "big nose" is an unusually specialized trait for a basal ornithopod like this, making its head more similar externally to that of a Late-Cretaceous hadrosaurian than to a camptosaur or tenontosaur. No fossil hands are known from ''Muttaburrasaurus'', but is typically represented with well-developed thumb-spikes in drawings -- even though their presence is impossible due to its primitiveness. In the ornithopods' modern phylogenetic tree ''Muttaburrasaurus'' is considered even more primitive than ''Camptosaurus'' despite living after the latter: thus is considered a late-surviving basal animal, like ''Leaellynasaura'', ''Minmi'', and the neighboring giant amphibian ''[[UsefulNotes/PrehistoricLifeOtherExtinctCreatures Koolasuchus]]''. It seems Australian, Antarctic and (in part) South-American fauna remained primitive across the Mesozoic, perhaps until the Great Extinction of 65 mya. Also, modern mammalian fauna of Australia and (in part) of South-America is rather peculiar compared with the ones of the other continents, while Antarctica has lost it completely when it froze, during the Mammal Age, aka the Cenozoic.

''Muttaburrasaurus'' appeared prominently in the classic Series/WalkingWithDinosaurs documentary of 1999 (in the fifth episode) as the biggest animal of its fauna, with speculative airsacs on its nose to make loud sounds; and also in the third sequel of ''The Land Before Time'' (rather incorrectly-portrayed, in truth), together with ''Hypsilophodon'' and ''Nodosaurus'' (see above).

Dinosaur names are often thought bizarre-sounding, and ''Leaellynasaura'' certainly does match the commonplace very well, like its bigger compatriot ''Muttaburrasaurus''. This one is called from the village of Muttaburra in Queensland, Australia, where its only skeleton was found in 1981; ''Leaellynasaura amicagraphica'' was named after the daughter of its discoverers, Leaellyn. Another little-known Australian dinosaur, ''[[UsefulNotes/PrehistoricLifeBirdlikeTheropods Timimus]]'', was named after Leaellyn's brother, Tim. It has ''mimus'' at the end because was originally thought an ornithomimosaur. ''Leaellynasaura'' (sometimes misspelled "''Leaellynosaura''") owes well its feminine suffix ''saura'', just like the hadrosaur ''Maiasaura'' which means “good-mother lizard”. Together with the shorter-named but equally bizarre-sounding ankylosaur ''Minmi'', these are the most well-known Aussie Dinos. First-found in 1989, ''Leaellynasaura'' was a small (1 m long) bipedal animal similar to ''Hypsilophodon''. Once considered an “hypsilophodontian”, even its ornithopod status is disputed today, and is now generally regarded as a more basal ornithischian. The fossil material attributed to ''Leaellynasaura'' [[http://espace.library.uq.edu.au/view/UQ:320937 has been recently revised]]. Fossils discovered in Australia in the 2000s indicate presence of a small Early Cretaceous ornithischian with tail 3 times longer that its own body (even more than the ''Tenontosaurus'' tail); whether this is the same taxon as ''Leaellynasaura'' or not remains to be seen.

The discovery of ''Muttaburrasaurus'', ''Minmi'', and ''Leaellynasaura'' in the 1980s made sensation in Australia, because very few dinosaurs were known before in the LandDownUnder, all fragmentary. ''Muttaburrasaurus'' still is one of the most complete dinosaurs found there; ''Leaellynasaura'' ‘s skeletons are more incomplete, but the latter's importance was due to having contributed to enforce the “warm-blooded dinosaurs” hypothesis even more. In Early Cretaceous, Australia was not the temperate/tropical/desertic country we know today, but a colder world with warm summers but cold winters - because was much closer to the South Pole. How could such a small, clearly non-migratory animal like this manage to survive that icy winter? The only explanation was: ''Leaellynasaura'' was warm-blooded. Furthermore, its unusually big eyes could have been used to see throughout the darkness of the polar winter. All these arguments have been discussed in ''Series/WalkingWithDinosaurs'', in which a family of ''Leaellynasaura'' makes the main characters. The show also portrayed ''Muttaburrasaurus'', as a migrating animal that flees the winter in herd like caribous; it also added to it speculative nasal sacs to make loud sounds (like what's been hypothesized for some hadrosaurs), but we don't have direct evidence for this.

''Camptosaurus'' ("bent lizard") was similar to ''Iguanodon'' above, but smaller (5-7 m long) and with mere hints of thumbspikes -- some portrayals show ''Camptosaurus'' totally spike-less or with fully-developed ''Iguanodon''-like spikes, both incorrect. It had the same bulky body, horse-like head, and general shape of ''Iguanodon'', but was probably more bipedal than the latter. It also preserved the ancestral forth digit in its feet, lost in ''Iguanodon'' and the hadrosaurs: indeed, ''Camptosaurus'' was one of the most primitive big ornithopods and one of the most basal thumb-spiked iguanodonts (properly known as [[http://en.wikipedia.org/wiki/Ankylopollexia ankylopollexians]]s, meaning "hooked thumbs"). In the Jurassic world still dominated by sauropods, camptosaurids and stegosaurians were the only big ornithischians that were successful, anticipating the great diversity bird-hipped dinosaurs reached later in the Cretaceous.

Also in Late Jurassic USA, alongside ''Camptosaurus'' the Wildebeest and ''Dryosaurus'' the Gazelle, we have ''[[RuleOfThree Nanosaurus]]'' the Dik-Dik. Meaning "dwarf lizard", this was indeed a very small animal, 1.5 m long (smaller than an ''Hypsilophodon''), with a very convoluted ScienceMarchesOn story on par with that of ''Edmontosaurus''. Discovered in 1877 during Cope’s and Marsh’s “Bone Wars”, ''Nanosaurus agilis'' ("agile dwarf lizard") was very commonly portrayed in old textbooks for having detained the record of “the smallest North American dinosaur” for almost a century. But in the 1970s, its validity was called into question due to the fragmentary nature of its remains. Also in the 1970s, a similar animal, ''Othnielia rex'', was described from the same sites, only to be renamed in 2007 as ''Othnielosaurus consors'' (both names derived from Othniel Charles Marsh) after many of the remains were reassigned to another dinosaur called ''Laosaurus celers''. Additionally, in 1990, a fourth dinosaur from the same habitat was named ''Drinker nisti'', after Marsh's rival Edward Drinker Cope! Finally, in 2018, newly discovered and better quality fossil material revealed ''Othnielia'', ''Laosaurus'', ''Othnieliosaurus'', and ''Drinker'' to all be the same as ''Nanosaurus'', thus taking several dinosaurs all known from a multitude of scrappy materials and merging them into one animal known from a large amount of material.

One of the most iconic scenes in those paleo-artistic works made in full Dino-Renaissance was a fight between a whole pack of ''Deinonychus'' and a much heavier ornithopod. Even though ''Iguanodon'' was often chosen in this role, the most classic choice has been another relative, ''Tenontosaurus tilletti'' ("Tillett's tendon lizard").

This was one of the most basal known iguanodontians, an Early Cretaceous animal similar in size to the more evolved but earlier ''Camptosaurus'' from Jurassic. Unlike the latter, the tenontosaur was totally devoid of thumbspikes (being more basal than the "ankylopollexian" iguanodontians, just like ''Dryosaurus''), and like the dryosaur it was [[ScienceMarchesOn once considered]] an overgrown "hypsilophodont" in older classifications - more precisely, the by far biggest member of the group. It had long front limbs (classic portrayals often show it quadrupedal) with five similar digits each, a long neck, a small head, and the primitive four-fingered hindfeet of basal ornithopods, but its most distinctive trait was surely its tail: it was much longer than most other relatives, ''twice'' the length of the rest of its body, and often depicted as a sort of "whip" almost like the tail of a diplodocid sauropod -- but it could have actually been more rigid than often shown.

First found in the 1970s in Montana, the first tenontosaur skeleton was surrounded by several ''Deinonychus'' skeletons. It was just this detail that made John Ostrom to think about these predators as wolf-like pack-hunters capable to bring down giant preys with their agility and their sickle-claws; ''Tenontosaurus'' has thus given an indirect contribute to the public image of dinosaurs.

In these struggles, ''Tenontosaurus'' is usually shown swinging its enormous tail and hitting some “raptors” to death, before being killed and eaten by the remaining ''Deinonychus''. The Tenontosaur-Deinonychus battle is more justified than the Iguanodon-Deinonychus one, both because the former has at least one possible proof, and because an adult ''Iguanodon'' would have weighed ''eighty times'' more than ''Deinonychus'' (see RaptorAttack). Some scientists, however, [[ScienceMarchesOn have recently suggested]] that the carnivores simply ate the carcass of the ''Tenontosaurus'' they found already dead. The presence of their skeletons around the herbivore could be explained if some “raptors” fought each other to the point that some ended killed by their own companions.

Maybe the first mention of ''Tenontosaurus'' in popular culture is in the first ''Franchise/JurassicPark'' novel: here the whole ''Deinonychus''/''Tenontosaurus'' thing is referenced, but Alan Grant attributes it to ''Velociraptor'' instead of to ''Deinonychus'' -- perhaps the greatest proof that the latest one ''is'' the chosen raptor in the story. The "tenonto" also appears in ''Series/JurassicFightClub'' as the victim of a pack of deinonychuses. Finally, ''Tenontosaurus'' is also one of the chosen dinosaurs for TheEighties / TheNineties expo called [[http://en.wikipedia.org/wiki/Dinamation Dinamation]], which showed several animatronic self-moving life-sized puppet-dinosaurs in various museum around the world as a further attraction other than the usual mounted skeletons and painting murals. Here, too, it is shown as the meal for a group of ''Deinonychus''.

''Hypsilophodon'', ''Dryosaurus'' and ''Tenontosaurus'', the three traditionally most-known "hypsilophodonts", were Jurassic or Early Cretaceous; but Hypsilophodon-like animals existed also in Late Cretaceous, even though they tend to be overshadowed in paleo-art by the spectacular ornithischians of their period: hadrosaurs, ceratopsians, ankylosaurs, and pachycephalosaurs. In North-America, while [[UsefulNotes/PrehistoricLifeHadrosaurs duckbills]] ruled the “wildebeest” role played by the camptosaurs in the Jurassic and by the ''Iguanodon''s in Early Cretaceous, the “gazelle” one was mainly played by ''Thescelosaurus neglectus''. ''Thescelosaurus'' ("marvelous lizard") was 3-4 m long and lived at the extreme end of the Cretaceous, 68-66 mya. Rather similar to ''Dryosaurus'' in appearance, it was once placed in the monotypic Thescelosaurid family, and sometimes believed a small iguanodont like ''Dryosaurus'' or another late-survivor, the European ''[[UsefulNotes/PrehistoricLifeHadrosaurPredecessors Rhabdodon]]'': but cladistic research have revealed it was not a basal iguanodont like ''Dryosaurus'' was. Rather robustly-built if compared with ''Hypsilophodon'', the thescelosaur had some small bony scutes on its back, maybe placed under the skin and not-visible in the living animal. Recently, ''Hypsilophodon'' as well has revealed these osteoderms, which were arguably for defense.

''Thescelosaurus'' is the animal from which the controversial “fossilized heart” comes from, which is almost certainly a fossilization artifact: that is, a piece of stone found in one specimen, which casually resembles a heart. Discovered in year 2000, this stony concretion was celebrated as the proof of “warm-bloodedness” among dinosaurs, because it seemingly showed a four-chambered heart just like bird and mammals and unlike most modern reptiles -- crocodilians have four-chambered hearts, but their ancestors could have been warm-blooded as hypothesized in the late 2000s. ''Thescelosaurus'' was one of the very few dinosaurs that managed to see the [[RockFallsEveryoneDies asteroid]] at the end of the Dinosaur Era, just like ''Tyrannosaurus rex'' and ''Triceratops'', other than ''Edmontosaurus'', ''Ankylosaurus'', and others, all from the Hell Creek Formation.

There were other “hypsilophodontians” from Late Cretaceous North America that were smaller and lived slightly earlier than ''Thescelosaurus''. They make together the Thescelosaurids, furtherly divided in the Thescelosaurines and the Orodromines. ''Orodromeus makelai'', meaning "Makela's runner of the (Egg) Mountain", is the prototype of the orodromines and was discovered in Montana in year 1988 by Jack Horner and his assistant Robert [[ExactlyWhatItSaysOnTheTin Makela]] in the same site in which they had found ''Maiasaura peeblesorum'' eight years before. They noted some small unusually spiral-shaped nests full of eggs containing fossilized embryos, next to the bigger & more famous ''Maiasaura'' ones, which they attributed to ''Orodromeus'': as the bones inside those eggs were already well-formed, they said that the orodromeus' hatchlings were more independent after birth than the maiasaura's ones. ScienceMarchesOn however, and later it was found that those eggs/embryos were from the theropod ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Stenonychosaurus]]'' instead. The ironical thing is, fossils of stenonychosaurs (aka the "troodons") were discovered as well around those putative ''Orodromeus'' nests, but it was thought that they were actually preying on Orodromeus nestlings: an astonishingly similar story to the “Oviraptor robbing Protoceratops' eggs”. Found in 2007, its relative ''[[http://en.wikipedia.org/wiki/Oryctodromeus Oryctodromeus]]'' ("digging runner") lived quite a bit earlier than the similar-named ''Orodromeus'' in Middle Cretaceous, but has also shown the first proof of digging behavior among non-avian dinosaurs: its skeleton has been found inside a fossilized burrow. Another relative found in Alberta is known since the start of the XX century: ''[[http://en.wikipedia.org/wiki/Parksosaurus Parksosaurus]]'' ("William Parks' lizard", sometimes misspelled "''Parkosaurus''"). Similar in size and shape to ''Orodromeus'' but living few million years later, it is known from a skull and a partial skeleton. ''[[http://en.wikipedia.org/wiki/Zephyrosaurus Zephyrosaurus]]'' ("lizard of the western wind"), lived earlier than all these, in the Early Cretaceous Montana: it could have met ''[[UsefulNotes/StockDinosaursSaurischianDinosaurs Deinonychus]]'' in real life, and possibly was one of its preys.

There were many non-hadrosaur ornithopods as well, but only one of them has made significant appearances in fiction, ''Iguanodon'' (again, this is the biggest of the ensemble). If you are lucky the much smaller ''Hypsilophodon'' may also show up, but it's almost never named. Both were Early Cretaceous. And if you're even luckier you might see the Late Jurassic ''Camptosaurus'' and ''Dryosaurus'', the first similar to ''Iguanodon'', the second to ''Hypsilophodon''. Worthy of note are also ''Tenontosaurus'' and ''Ouranosaurus'' because are strongly-associated with one famous predatory dinosaur each (''Deinonychus'' and ''Spinosaurus'' respectively); ''Muttaburrasaurus'' and ''Leaellynasaura '' are known for being rare examples of Australian dinosaurs; ''Thescelosaurus'' and ''Orodromeus'' are the animals the controversial "pietrified heart" and the "pietrified nests" were attributed to, respectively. ''Heterodontosaurus'', ''Lesothosaurus'', ''Fabrosaurus'', and ''Scutellosaurus'' are here for convenience, but are not true ornithopods anymore according to modern knownledge. In the last years even ''Hypsilophodon'', ''Leaellynasaura'', ''Orodromeus'', ''Thescelosaurus'' and tiny ''Nanosaurus'' have been put outside Ornithopods proper, and now are often considered "basal ornithischians" by many.

Living 126 to 125 million years ago in Early Cretaceous Europe, this is one of the most iconic non-avian dinosaurs from the "old continent" together with ''Compsognathus'', ''Plateosaurus'', ''Megalosaurus'', ''Baryonyx'', and to an extent, ''Archaeopteryx''. It’s also one of the most scientifically well-known dinosaurs, and one of the most abundant in fossil record. ''Iguanodon'' has had a special role within the stock dino-ensemble. Along with ''Megalosaurus'' and ''Hylaeosaurus'', it’s the only dinosaur that has covered the whole history of scientific and popular portraits, but unlike the today rarely-portrayed megalosaur & hylaeosaur, has managed to be still common today in pop-media.

Although nearly as big as ''Tyrannosaurus'' (10 m or more, and up to 4 tons), ''Iguanodon'' has not an especially striking look among Stock Dinosaurs. Being an earlier relative of hadrosaurs and possibly their ancestor, its shape resembled one of the latter, with three-toed hindfeet, flexible neck (but less so than hadrosaurs), long muscular tail stiffened by bony tendons, massive body, hindlimbs longer and stronger than forelimbs. Non-hadrosaurian traits include: the backbone not curved at the shoulder level; grinding teeth much less numerous and put in one single row on each half-jaw like almost all non-hadrosaur dinosaurs; a totally crest-less, bump-less head; a deep, narrow beak very unlike the duck-billed one.

The hands of ''Iguanodon'' contain all the "oddities" in its skeleton. The most known is the [[HookHand spike on its hand]], made of the first digit's phalanxes fused together and encapsulated in a horny sheath, usually shown in books as a weak weapon against enemies. And it had a very flexible, opposable "pinkie" finger, maybe to grasp vegetation. Hadrosaurs too had a little-finger in their hands other than the three main digits, but was smaller than the iguanodon's one and maybe useless and vestigial. Like hadrosaurs, the three central fingers of ''Iguanodon'' were fused together in a hoof-like structure and supported the weight of the dinosaur when on four legs, though incorrect freely-fingered iguanodonts-hadrosaurs often appear in portraits.

We don’t know for sure if iguanodonts and hadrosaurs were mainly tree-browsers or ground-grazers. However, classic portraits usually show iguanodonts in the usual "tripodal" stance and browsing like a giraffe. Several paleo-works have also added a long extendable giraffe-like tongue to reach tree-foliage, but this is unlikely. In these old portraits, ''Iguanodon'' was substantially the reptilian equivalent of the giant ground sloth ''[[UsefulNotes/StockDinosaursNonDinosaurs Megatherium]]'', also often portrayed as an upright tree-browser with horsy head, robust clawed forelimbs, giraffe-tongue, and tail used as a tripod together with the hindlegs.

''Iguanodon'' is one of the three animals along with ''Megalosaurus'' and the ankylosaurian ''Hylaeosaurus'' which were called "dinosaurs" for the first time in history (1842), by the English paleontologist [[http://en.wikipedia.org/wiki/Richard_Owen Richard Owen]]. ''Iguanodon'' was already identified in 1825, just one year after ''Megalosaurus'', by English doctor and fossil-collector Gideon Mantell: it's the second non-bird dinosaur to have received an official name. It was initially described from its iguana-like teeth and few other incomplete remains: hence its name meaning ''iguana's tooth''. But then, in 1877 [[SocialOrnithopod about 40]] ''Iguanodon'' skeletons were discovered within a coalmine in Belgium near the town of Bernissart, the very first "dino graveyard" ever found. These remains were named ''Iguanodon bernissartensis'' and described by Belgian zoologist Louis Dollo. Many other remains were later assigned to ''Iguanodon'', often found outside Europe, but many have recently split in other genera, making it a brand new wastebin taxon other than the more classic "Megalosaurus wastebasket". One of these genera is named ''Mantellisaurus'' after Gideon Mantell.

Most dinosaurs have changed their look at least once: ''Iguanodon'' has done this ''twice''. The first attempt of reconstruction showed [[http://www.places-to-go.org.uk/crystal_palace_iguanodon.htm a huge dragon-like quadruped]], and one of its thumbspikes was inaccurately put on its nose--this is justified by the very fragmentary nature of its original remains. The life-sized ''Iguanodon'' and other extinct animals were sculpted by Benjamin Waterhouse Hawkings and shown to public during the 1856 Universal Exposition in London, in the famous Crystal Palace. A banquet was organized to celebrate the event… inside the still incomplete iguanodon model! Even though the palace got ultimately destroyed by a fire, the sculptures survived the incident, and are still visible in the eponymous park.

After the discovery of the complete skeletons from the "dinosaur mine" in the 1870s, the iguanodon became [[https://youtu.be/pQJIVxzIUic bipedal and upright, but still reptile-looking]], often shown with iguana-spikes running along its back, and with an overall theropod appearance. Finally, studies started in the 1970 and led by English paleontologist David Norman made Iguanodon returning quadrupedal again (though still capable to stay and run on two legs), and with cheeks hiding the teeth in the living animal. [[note]]Once, all ornithischian dinosaurs were portrayed with no cheeks and a wide mouth running from ear to ear, like saurischian dinosaurs: this was based on modern reptile, which are unvariably cheek-less. The shape of ornithischian jaws showed they could have had cheeks to store plant matter during th mastication, like modern herbivorous mammals. This is confirmed by the "hadrosaurs mummies." If alive today, ornithischians’ head would resemble an [[MixAndMatchCritter ungulate mammal but with a beak]].[[/note]] An excellent example of this new portrait is seen in Disney's ''WesternAnimation/{{Dinosaur}}'', which made ''Iguanodon'' the main character in the story -- [[ExecutiveMeddling exaggerating its horse-like look]] with fleshy lips instead of the proper bill, and showing it running always on all fours like an actual horse.

Even though has been extremely common in dino-books and other non-fictional media, ''Iguanodon'' has not made significative apparitions in cinema or TV before Disney's ''WesternAnimation/{{Dinosaur}}'' and ''Series/WalkingWithDinosaurs'' were broadcast during the [[TurnOfTheMillennium 20th-21st century change]]. The most recent one is in 2022's ''[[Film/JurassicWorldDominion Jurassic World Dominion]]''. RuleOfCool easily explains why: with its generic look and weak weapons, it don’t bear the comparison with ''UsefulNotes/TyrannosaurusRex'' jaws, ''[[TemperCeratops Triceratops]]'' horns, ''[[ToughArmoredDinosaur Stegosaurus]]'' plates, "[[RaptorAttack raptor]]" claws, or the immense size of [[GentleGiantSauropod sauropods]] -- and some portraits could even leave the beak or the thumbspikes substituting them with a lizard-head and generic hands, making it even more inconspicuous. However, its historical and scientific importance won't ever be deleted in dino-fans' consciousness, as no other dinosaur has run the whole two centuries of popular portraits: from [[https://youtu.be/rgqQNBuGGWg Crystal Palace rhinos, to giant two-legged iguanas, up to Disneyan horses]].

When we think about small bipedal dinosaurs our mind automatically comes to guys like the “raptors”, the “compies”, the ornithomimids, or the oviraptorids, all theropods. But there were also several ornithopods which shared an analogue body-shape with the latter; even though they are usually ignored by film-makers. The most iconic of them has always been ''Hypsilophodon''.

One of the first dinosaurs discovered, in the middle XIX century, lived in Europe 130-125 million years ago together with its gigantic relative ''Iguanodon'', and was originally considered the latter’s juvenile specimen. Unusually for such a small animal, [[SocialOrnithopod dozens complete individuals have been found]], and this also explains its historical role as the stock small ornithopod. Most remains come from England, especially the southern Isle of Wight, home of many other Early Cretaceous English dinosaurs; but some uncertain remains attributed to ''Hypsilophodon'' come from North America and Spain.

A very small dinosaur, 2 m long or less, the bulk of a large dog, ''Hypsilophodon foxii'' ("Fox's high-crested tooth") is easily distinguishable from theropods by its horny beak on the lower jaw, small mouth-opening typical of ornithischians, large grinding teeth at the bottom of the mouth hidden by cheeks in the living animal (but also smaller teeth on the tip of the upper jaw, a primitive trait among ornithischians), hands with five digits - coelurosaurs never have more than three fingers - and a more round belly to contain the typical large gut of a herbivore.

''Hypsilophodon'' is nicknamed “the gazelle dinosaur”. The comparison works very well: it was a graceful, harmless, wide-eyed biped that escaped predators thanks to its agile legs well adapted for high-speed runs: it was certainly one of the quickest-running dinosaurs. If alive today, it would probably appear one of the cutest-looking dinos, maybe even suitable as a good [[KidsLoveDinosaurs household pet]].

But before the 1970s, ''Hypsilophodon'' used to be depicted as a tree-climbing animal, vaguely similar to a large, long-legged, spike-less green iguana, and long depicted in this way in books, 3D models, and sometimes even fiction. This is how it is shown, for example, in ''Fantasia''-- the tiny green tree-climbing dinosaurs that the ''Stegosaurus'' disturbs are ''Hypsilophodon''. Few other dinosaurs have had such a great ScienceMarchesOn change during their story: maybe only ''Spinosaurus'', ''Megalosaurus'' and ''Iguanodon'' can rival it in this area. While ''Iguanodon'' was often reconstructed using a classical kangaroo as a model, ''Hypsilophodon'' was often compared with the "[[http://en.wikipedia.org/wiki/Dendrolagus tree-kangaroo]]", a small kangaroo living in the canopy of the forests of New Guinea and northern Australia.

In the rare event this little critter is portrayed in Fictionland, expect it to be portrayed as the dinosaurian RedShirt, little more than a bite-sized snacklet for the big hungry carnivores. This portrayal can be shared with small theropods as well, especially the toothless ones. Hypsilophodonts are often cited with ornithomimids as examples of harmless dinos: ostrich-dinosaurs too had a graceful appearance, large eyes, and were fast runners, but are more strongly associated with birds in public mind than the small ornithopods like ''Hypsilophodon'' (and were also closely-related to them). A singular case is in ''[[WesternAnimation/TheLandBeforeTimeIIITheTimeOfTheGreatGiving The Land Before Time 3]]'', in which the leading villain of the story is a strange-looking puppy of ''Hypsilophodon'' named [[ALizardNamedLiz Hyp]] who is the leader of a TerribleTrio of young dino-rivals of the protagonistic FiveManBand (Littlefoot, Cera, Spike, Ducky, Petrie).

''Hypsilophodon'' has always been quite common in paleo-art and dino-books; for example, the portrayal made by John Sibbick in the "Great Dinosaur Encyclopedia" depicted the animal with a green hide and eyes with cat-like pupils. Obviously, we don't know if the hypsilophodont was really green and cat-eyed; however, this reconstruction has inspired several other further "hypsies" paleo-artistic depictions. As the picture was from 1985, the animal is shown scaly; today many scientists think it was covered by feather-like structures like other ornithischians.

Let’s face it: it’s RuleOfCool that undisputedly dominates when coping with dinosaurs. ''Camptosaurus'' is the perfect example. This is one of the most abundant dinosaurs in fossil record, with both young and adult specimens known, and also one of the most common dinosaurs in museums around the world: this abundance in museums is even referenced in the first Franchise/JurassicPark book, in which the boy Tim brings his father in a natural-science museum and shows him the first dinosaur skeleton they meet just belonging to a juvenile ''Camptosaurus''. But when was the last time you’ve you watched it in recent documentaries other than ''Series/PlanetDinosaur'', which portrays it as a simple fodder for the allosaurs?

''Camptosaurus'' lived in Late Jurassic North America just alongside: ''Brontosaurus'', ''Diplodocus'', ''Brachiosaurus'', ''Stegosaurus'', and indeed ''Allosaurus'': it could have shown up in ''Series/WalkingWithDinosaurs'', ''Series/TheBalladOfBigAl'' or even ''WesternAnimation/WhenDinosaursRoamedAmerica''. Maybe its rather generic appearance (by dinosaur standards of course) was judged kinda inconspicuous to capture the watchers’ interest. Other two very important Late Jurassic U.S. dinosaurs unfairly missed by the Walking With series are the sauropod ''Camarasaurus'' and the theropod ''Ceratosaurus'', both at least appearing in WDRA.

''Camptosaurus'' ("bent lizard") was similar to ''Iguanodon'' above, but smaller (5-7 m long) and with mere hints of thumbspikes -- some portrayals show ''Camptosaurus'' totally spike-less or with fully-developed ''Iguanodon''-like spikes, both incorrect. It had the same bulky body, horse-like head, and general shape of ''Iguanodon'', but was probably more bipedal than the latter. It also preserved the ancestral forth digit in its feet, lost in the ''Iguanodon'' and the hadrosaurs: indeed, ''Camptosaurus'' was one of the most primitive big ornithopods and one of the most basal [[http://en.wikipedia.org/wiki/Ankylopollexia ankylopollexians]], meaning "hooked thumbs" in reference to their thumbspikes. ''Camptosaurus'' was a possible ancestor of ''Iguanodon'' and, indirectly, duckbills. In the Jurassic world still dominated by sauropods, camptosaurids and stegosaurians were the only big ornithischians which were successful, anticipating the great diversity bird-hipped dinosaurs reached later in the Cretaceous.

The most known ''Camptosaurus'' species is ''Camptosaurus dispar''; other alleged ''Camptosaurus''es found in Europe (Portugal and England) actually pertain to other genera. It could have fallen prey to ''Ceratosaurus'' and ''Allosaurus'': but a fully-grown, 7 m/20 ft long ''Camptosaurus'', the same length of a 1-ton ''Ceratosaurus'' but heavier than it, 2 tons, could have defended itself against it like a wildebeest or a zebra against predators smaller than a lion.

The other well-known Late Jurassic ornithopod, ''Dryosaurus altus'' ("tall oak-lizard"), was even less-conspicuous than ''Camptosaurus'', but has received a slightly better treatment showing up in all the three documentaries above, all made around the TurnOfTheMillennium, though with very minor roles -- in one case, it serves only to give a prey to ''Allosaurus'' -- but it doesn't appear in TheNewTens-related ''Series/PlanetDinosaur''.

''Dryosaurus'' was smaller than ''Camptosaurus'' and much more slender, similar to a ''Hypsilophodon'' in shape being totally bipedal. Compared with ''Hypsilophodon'', the dryosaur was larger (3-4 m long), slightly more robust, with a shorter head, toothless upper beak other than the lower, and lacking the forth reversed toe of ''Hypsilophodon'' and (ironically) the closer-to-Iguanodon ''Camptosaurus''. Like the camptosaur ''Dryosaurus'' was actually a basal iguanodont and not an hypsilophodont, and the prototype of its own lineage, the Dryosaurids; but was [[ScienceMarchesOn once]] considered a big "hypsilophodont", as big as the Late Cretaceous ''Thescelosaurus'' made famous in year 2000 for being the owner of the presumed "petrified heart" that led so much controversy about dinosaurs' warm-bloodedness.

Both discovered during the Bone Wars, ''Camptosaurus'' and ''Dryosaurus'' have been found in the USA. Specimens once referred to ''Dryosaurus'' have also been discovered in Africa - more precisely in Tendaguru, together with ''Giraffatitan'' and ''Kentrosaurus''; they have been recently re-classified as ''[[http://en.wikipedia.org/wiki/Dysalotosaurus Dysalotosaurus]]''. Other were found in Europe, but are actually from other ornithopods.

''Camptosaurus'' and ''Dryosaurus'' are very frequently portrayed in dinosaur books, especially the former; here both are typically shown as among the favorite preys of ''Allosaurus'' or ''Ceratosaurus'', a concept that is almost certainly true. Indeed, in North American placements, camptosaurids and dryosaurids were respectively the “wildebeest” and the “Thompson’s gazelles” of their fauna, that escaped their reptilian “lions” and “hyenas” (allosaurs and ceratosaurs indeed) by running quick on two legs. Dryosaurids, being smaller and more maneuverable, were probably faster than camptosaurids, but the latter, being bigger and with a stronger physic, had more chances to defend themselves effectively against their predators. Both dryosaurs and camptosaurs were herd animals, as shown by the numerous individuals found together in fossil sites.

Always in Late Jurassic USA, other than ''Camptosaurus'' the Wildebeest and ''Dryosaurus'' the Gazelle we'd encounter also ''[[RuleOfThree Nanosaurus]]'' the Dik-Dik. Meaning "dwarf lizard", this was indeed a very small animal, 1.5 m long (smaller than an ''Hypsilophodon''), with a very convoluted ScienceMarchesOn story. Discovered during Cope’s and Marsh’s “war”, ''Nanosaurus agilis'' ("agile dwarf lizard") was very commonly-portrayed in old textbooks for having detained the record of “the smallest North-American dinosaur” for almost a century. In 1977 it was described from the same sites a similar animal, ''Othnielia rex'', which was renamed more recently ''Othnielosaurus'' because its type material was not diagnostic. Both curious names derive from [[http://en.wikipedia.org/wiki/Othniel_Charles_Marsh Othniel Charles Marsh]], one of the two scientists who “fought” the Bone-Wars in the XIX century. As it seems, its notorious rivalry with [[http://en.wikipedia.org/wiki/Edward_Drinker_Cope Edward Drinker Cope]] has lasted until today, with another similar animal from the same habitat named ''Drinker nisti'' in 1990 out of spite!

Today, all these three genus names are usually considered as junior synonyms of ''Nanosaurus agilis''. Today, the record of "the smallest North-American dinosaur" pertains to a tiny heterodontosaurid found only in 2009, ''[[UsefulNotes/PrehistoricLifePrimitiveOrnithischians Fruitadens]]''. The very fragmentary ''[[http://en.wikipedia.org/wiki/Laosaurus Laosaurus celer]]'' ("speedy fossil lizard", described in USA in the same period of ''Nanosaurus'') has been involved in this taxonomic tangle as well, with its remains often found mixed with those of ''Dryosaurus''.