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This page is about the stock ornithischian dinosaurs. Ornithischians ("bird-hipped dinosaurs") included a variety of usually herbivorous dinosaurs, from Ceratopsians to Stegosaurs, to Ornithopods, to Ankylosaurs, to still others: some big and other small, some bipedal and other quadrupedal, and others in part bipedal in part quadrupedal. All were accomunated by their skeletal anatomy, expecially their specialized jaws, and this time were surely a natural grouping of dinosaurs that arose in the Triassic from a still-unknown common ancestor. They eventually went extinct 66 mya in the Mass Extinction that ended the Mesozoic, this time without leaving descendants.

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Armor-bodied Plant-Eaters

The Thyreophorans ("shield bearers"), were a group of dinosaurs notable for their body armor made of bony plates covered with horny sheaths. Many also developed weapons on the tips of their tails. All but the most primitive forms were massive quadrupedal animals belonging to one of these two groups: stegosaurians and ankylosaurians.

    Stegosaurians 

Stegosaurians were small-headed, mostly Jurassic herbivores that developed large bony plates along their backbone for uncertain purposes, and had pairs of spikes on their tail and sometimes on their hips or shoulders as well. Stegosaurus is the namesake of the group as well as one of the largest known members, while Kentrosaurus was one of the smallest and spikiest of them. Tuojiangosaurus was rather in the middle of the two both in size and in look.

Plates as Solar Panels?: Stegosaurus ***

https://static.tvtropes.org/pmwiki/pub/images/stegosaurus_-_copia_4758.jpeg

Lived in Late Jurassic North America, 155 to 150 million years ago, and was discovered during the Bone Wars like several other Stock Dinosaurs (Allosaurus, Diplodocus, Brontosaurus etc.) note  One of the most easily-recognized dinosaurs thanks to its bony plates, spiked tail and distinctive silhouette, Stegosaurus has always been one of the most iconic dinosaurs of all, along with T. rex, Triceratops, and a token sauropod. It is regularly portrayed both in films and in cartoons.

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 looking bigger than it was when seen from the side: actually, the stegosaur’s body was laterally-flattened, and not so heavy as it seems. Its limbs were pillar-like; the front legs were much shorter than hindlegs, 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 Dumb Dinos 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 purposals.

The plates is the distinctive stegosaurian feature, and every stegosaur portrait shows them. But it isn't entirely clear what their purpose was. It was debated whether the plates were covered in horn or in skin, but a study on stegosaur skin impression suggests the former is more likely. Defense, thermoregulation, and display (mating or threat) are the classic hypotheses, but we haven’t definitive proof for any. The early theory that they were used for armor is the most unlikely: the plates were dermic structures not attached to the skeleton, and they were irregularly placed to be used as armor and would leave the animal's sides unprotected — although if covered in horn they might have had sharp edges, which would make them effective as defense. The "solar panel/radiator" theory has been one of the most followed since the Dino-Renaissance: it could explain why they apparently were so rich in blood vessels (their tissue was very spongy), and also the singular arrangement of these plates — they were asymmetrically-placed, giving more surface to solar rays. This theory is a concrete possibility, as studies on crocodilian scutes (also rich in pores and cavities) show they have usage for thermoregulartory purposes. Walking with Dinosaurs popularized the third theory, showing a Stegosaurus reddening its plates and scaring an Allosaurus away. However, if used for display, they might also have had the function of making the animal look larger if seen from the side, or communicating with others of its kind by changing hypothetically their colors, like what some modern reptiles do with their appendages. It's probable that all three theories are partially or completely true.

The configuration of these plates was until recently debated. Though Stegosaurus has left dozens of specimens, they are usually found with misplaced plates, making them a sort of puzzle to rebuild. All combinations were proposed, from a single line to two paired lines. One early theory was they were flat on the back like tiles: this gave to the dinosaur the odd name Stegosaurus, "roof-lizard". The first still-articulated stegosaur skeleton was found only in the 1990s, and shows alternated plates, confirming most of the earlier suppositions.

Stegosaurus' tail was shorter than that of most sauropods: it was muscular and flexible but not ending with a narrow "whip" like in diplodocid sauropods. The animal may have been able to rest it on the ground to assume a tripod stance and reach higher vegetation, just like what has been hypothized about sauropods. When swung from side to side, this tail made a powerful weapon against enemies. Near the tip of the tail was a group of four long spikes known as the thagomizer, a term that originates from a Far Side cartoon, later adopted by the paleontological community (you can find it used in serious scientific publications) in an even more awesome case of Ascended Fanon than the word "raptors".

Another curiosity, though, is rarely mentioned: Stegosaurus had small scutes on its hips and tiny osteoderms under its throat. Also, a study on one Stegosaurus species, S. sulcatus, suggests that a spike found alongside a specimen may be actually from the shoulder and not from the tail as previously assumed. If this is true, then Stegosaurus had shoulder spikes like its relatives. Interestingly, one of the very first portraits of the stegosaur showed it with spikes all over its body and a bipedal posture.

It has recently been suggested that Stegosaurus was sexually dimorphic but others have cast doubts on this.

If you see Stegosaurus in popular media, don't be surprised to see inaccuracies. To this day, it may be shown with paired plates or even plates in a single line, instead of zigzagging in two lines, and they may be round or triangular instead of pentagonal. And its tail may have two, three, five, six, or even eight spikes. The eight spikes portrayal first originated from an early reconstruction of Stegosaurus ungulatus made soon after its first scientific description, in late 1800. Or it can have no tailspikes at all. These spikes may be shown as much shorter than in reality: the fossil spikes were about three feet in length, and they might have been covered in horn which would have made them larger. They usually point upwards in images, while in reality they were more sidewards-pointing. In some cases the neck is unrealistically long, like Dinny in Alley Oop, making it resemble a cross between a stegosaurian and a sauropod. The body may be shown as very low-slung and fat even when seen from the front, and the legs are often stubby. Stegosaurus may often be depicted with a turtle-like face instead of a horse-shaped one like in real life. It can be shown with a beak full of teeth, or no beak at all, or fleshy lips and wide mouth opening, like a lizard.

In many old films, Stegosaurus is shown as a sorta "predestined loser" against big meat-eaters like Allosaurus, Ceratosaurus or Tyrannosaurus, being too slow to defend itself effectively. In modern portrayals, however, Stegosaurus more often wins fights with the aforementioned carnivores, like in Walking with Dinosaurs, as it is now considered to be agile and flexible in spite of its slow running speed and heavy body. Living in herds, as shown by the abundance of specimens in fossil record (it's believed the most common dino in the Dinosaur National Monument), this made further protection. No eggs and nests are known but many young individuals, with smaller plates/spikes and bigger heads than the adults.

  1. Entry Time: 1912
  2. Trope Maker: The Lost World

How many Spikes you Have: Kentrosaurus *

If you're watching a film or even a TV documentary, good luck if you’ll ever find a stegosaurian which is not Stegosaurus. However, if you do, it will probably be Kentrosaurus.

Only half the length of Stegosaurus, 4 meters, and weighing much less than it, it was one of the smallest members of the family. Its overall body shape was almost identical to the latter... except for the armor. The usual plates on the neck and back were much smaller and paired (not zigzaging), gradually becoming spikes on the hip and ending with at least five pairs of true spikes on the tail. But this is not all, Kentrosaurus had also a pair of isolated spikes arising from its shoulders — to the point it could earn the nickname "porcupinosaur".

A Late Jurassic animal like Stegosaurus, Kentrosaurus was discovered in the 1910s in the same East African site along with much bigger dinosaurs like Giraffatitan and other sauropods (which could easily trample it if it was not careful); the two stegosaurians couldn't have met each other in reality. Dozens of Kentrosaurus skeletons have been discovered but, like Stegosaurus, with plates/spikes scattered away: thus, scientists once thought Kentrosaurus side spikes were on its hips instead of its shoulders. That's why classic dino-portrayals show it with spikes protruding from the pelvis instead of from its forequarters.

One mention about [mis-]spelling: Kentrosaurus should never be confused with Centrosaurus . Both names mean "pointed lizard", but the "points" of Centrosaurus were on its head: it was a ceratopsian. In some old sources Kentrosaurus is known as "Kentrurosaurus" ("pointed-tailed lizard"), but this name is now invalid.

  1. Entry Time: 1980s
  2. Trope Maker: Dino-Riders

The Unpronounceable: Tuojiangosaurus *

Together with Kentrosaurus, the most portrayed non-Stegosaurus stegosaur in popular dino-books has been Tuojiangosaurus ("Tuojiang's lizard") — don't worry if you cannot pronounce that "jiang" correctly, unless you are Chinese or Chinese-speaking of course. It whole scientific name is Tuojiangosaurus multispinus, "many-spiked Tuojiang's lizard": it owes its name from Tuo-Jiang, a Chinese location within the Szechuan province of China. Other two classic Late Jurassic dinosaurs from the same country have also geographically-referenced names, Mamenchisaurus ("Ma-Men-Chi lizard") and the allosaur-relative Yangchuanosaurus, "lizard of Yang-Chuan".

Discovered in 1977 and described by paleontologist Dong Zhiming, Tuojiangosaurus was overall more similar to Stegosaurus than to Kentrosaurus (some quote it an its "Asian variant"), but was slightly smaller than its U.S. cousin: "only" 7 m long, like the smallest adult Stegosaurus individuals. Despite this, its armor was rather of an intermediate between a Kentrosaurus and a Stegosaurus one. Tuojiangosaurus had narrow, paired plates like the former, but a four tail-spiked (thagomizer) like the latter. The plates of the tuojiangosaur were like sharp isosceles triangles unlike the more pentagonal or "diamond-like" ones of Stegosaurus, and its tail-spikes were a bit smaller; some pictures show Tuojiangosaurus with shoulder-spikes like those of Kentrosaurus, but it is unsure whether it had them. Anyway, with such small plates, it is more uncertain that Tuojiangosaurus and Kentrosaurus would have used them as solar panels or radiators than the wider-plated Stegosaurus.

Tuojiangosaurus is one of the classic dinosaurs from Jurassic Asia: it seems especially common in British dino-books, as a skeleton cast of it has been on display in the Natural History Museum of London since the 1980s, which is often shown in illustrations. The tuojiangosaur appears also in Jurassic World: the Videogame as one of the dinosaurs cloned in the park.

  1. Entry Time: 2010s
  2. Trope Maker: Jurassic World

Other stegosaurians

Sorry, these ones aren't here. If you're looking for Dacentrurus, Huayangosaurus, Wuerhosaurus, Chialingosaurus, Lexovisaurus, Loricatosaurus, Monkonosaurus, Gigantspinosaurus, Miragaia, and others, see here.

    Ankylosaurians 

These are the most well-armored among all the dinosaurs (sometimes called the armored dinosaurs), with low wide frames, quadrupedal stance, strong short legs and armor consisting of bony plates covering the upper part of their bodies. They were herbivorous and mostly lived during the Cretaceous, after most stegosaurians. They aren't as common as the stegosaurians in works, but still crop up semi-regularly both in fiction and in documentaries.

Ankylosaurians were once divided in only two families: ankylosaurids (clubbed) and nodosaurids (club-less). Ankylosaurids (among them Ankylosaurus, Euoplocephalus, Scolosaurus, and Pinacosaurus) had a broad head, their armor plates formed a keratin-covered shell with short spikes in many directions, and they had a tail club except for the most primitive forms; proper nodosaurids (including Nodosaurus, Sauropelta, and Edmontonia) had a narrow head, rows of osteoderms on their backs and flanks, and longer spikes jutting out sideways. In recent years a third subgroup has been recognized as distinct from nodosaurids: the polacanthids (including Polacanthus, Gastonia, and possibly Hylaeosaurus), variably classified as either closer to ankylosaurids or to nodosaurids. Finally, the early Jurassic Scelidosaurus was once considered basal between stegosaurs and ankylosaurs, but many today classify it as an extremely primitive ankylosaur well outside the three subgroups above.

The Living Tank: Ankylosaurus **

Lived in North America around 66-65 million years ago alongside Tyrannosaurus, Triceratops, and the "duckbill" Edmontosaurus, at the end of the Dinosaur Age.

Discovered in 1908 in Alberta, its actual size is uncertain: extimated from about 20 ft (6 m) long up to 9-10 m, the latter was believed the more likely until few years ago. It has traditionally believed the biggest known ankylosaurian, possibly weighing up to 6 metric tons, as much as a male African elephant, in the same weight range as Triceratops and the biggest Stegosauruses. Despite its size, its remains are quite scant, with still no complete skeletons found, and several other relatives are more common as fossils. Ankylosaurus' iconic status among ankylosaurians could be explained by its sheer size and because its own dinosaurian group is called by its name. Ankylosaurus was a strongly-armored ankylosaurian — several sources have described it as a "living tank".

Ankylosaurus has been famous since the 1940s as the Up to Eleven example of an armored dinosaur. In both fictional and documentary media it is often portrayed in a battle against T. rex, similarly to Triceratops. In these struggles the ankylosaur is seen defending itself by sheltering under its impenetrable bony armor, and using its tail-club like a Medieval mace, breaking the legs of its opponent and making it fall down. This might be Truth in Television, even though tyrannosaurs almost certainly didn't prey upon adult ankylosaurians frequently (hadrosaurs were much more abundants and armor-less). Despite their heavy build and short legs, ankylosaurians may have been able to charge the carnivore: their limbs were not pillar-like as the sauropods and stegosaurs, but more similar to those of a rhino or a hippo who are known for their fast charges. Like stegosaurs, ankylosaurs tend today to be portrayed as more agile and active in fights now than in the past: in Walking with Dinosaurs one easily wins the struggle (despite being shown as a very slow-walking animal), delivering to the carnivore a fatal blow with its tail-mace. When the tyrannosaur is shown winning the battle, it's seen "overturning" the ankylosaur to expone the soft vulnerable underbelly and devouring its flesh there.

Most herbivorous or omnivorous dinosaurs are often depicted in media as gregarious animals: scenes involving herd-dwelling sauropods/ceratopsians/stegosaurs/hadrosaurs/iguanodonts/ornithomimids are a very common sight. On the other hand, ankylosaurians are usually depicted as loners. This is realistic, because their fossils are more rare than those of other large herbivores and almost always found isolated. One rare exception is a group of about eight juvenile Pinacosaurus (see below) found together, which probably died at the same time during a sandstorm.

Ankylosaurus probably retains the record of being the worst-known Stock Dinosaur. Even in documentary works, its size, shape, and composition tend to be pictured incorrectly, often with traits from other ankylosaurian species. The incompleteness of the remains only partially justify this. One common mistake is to leave out the tail club, or to have it shaped incorrectly — for example, adding spikes to it. A famous example of the latter is the "Ankylosaurus" (actually a Scolosaurus) painted by Zdenek Burian defending itself against a tyrannosaurid: it is undersized and has two spikes on the tip of its tail. When based on Real Life fossils, the club usually appears two-lobed like that of a Euoplocephalus (a close relative commonly depicted in popular dino-books), instead of elliptical.

The bony covering on its back should be a snugly fitting mix of large and small plates and be interspersed with short spikes. Many classic portrayals, on the other hand, show long spikes only on the sides, similar to the related nodosaurids. Other portraits go even further, showing totally spikeless Ankylosauruses: see the aforementioned finale of Walking with Dinosaurs, in which Ankylosaurus has keeled plates instead of true spines. Finally, the broad head should have four horns behind the eyes and the ends of the mouth, but hornless Ankylosauruses are not unseen elsewhere.

Ironically, one of the few plausible ankylosauruses in cinema is the dog-like Url from Disney's Dinosaurs: he was highly undersized, but this may be justified if he was young. Another is in the controversial documentary Clash of the Dinosaurs, qualified by many as a Documentary of Lies, but at least has the merit to show the correct shape of its head. Still another rather correct Ankylosaurus is in The '90s-related Planet of Dinosaurs.

Many other inaccuracies seen in ankylosaur portrayals are substantially the same as the stegosaurs. Being related to each other, stegosaurs and ankylosaurs shared many features. They had the typical ornithischian jaws, with teeth only on the back and a toothless beak on the tip. However, their beaks and teeth were weaker than other ornithischians (ceratopsians, ornithopods); they may have chewed only soft plant material near the ground-level, and/or swallowed small stones to aid digestion, like sauropods. Even though were much smaller-sized, stegosaurians and ankylosaurians tend to be shown as slow-moving as the sauropods: ex. the aforementioned Url which has the slowest pace among all the dinosaurs of its herd, just as slow as its companion brachiosaur Baylene. Pre-"Renaissance" depictions used to portray ankylosaurians and other four-legged dinosaurs with splayed legs and dragging tails. Actually quadrupedal dinos had erect limbs (among them only sauropods had true claws, the others had blunt nails), and footprints show they usually kept their bodies and tails above the ground when walking around. Of course, expect to see splayed-limbed ankylosaurs even in relatively recent works — Rooter of The Land Before Time appears even slower than the sauropods of the same film (the latter have correct upright limbs, though).

  1. Entry Time: 1940s
  2. Trope Maker: "The Age of Reptiles" mural

Artistic Armor: Euoplocephalus & Scolosaurus *

Ankylosaurus magniventris ("big-bellied fused lizard") was the first clubtail recognized (1908), but, as said above, its remains were very scanty; however, its assumed record size (more than 10 m long) soon made it the prototype of the ankylosaurians. But North America was home for other clubtails as well, which lived slightly earlier than the namesake of the group (though all lived in the Late Cretaceous): the traditionally most-portrayed among them has been Euoplocephalus ("well-armored head", NOT to be misspelled "Euplocephalus" or "Eurocephalus" or "Enoplocephalus" or so on).

Euoplocephalus tutus lived 75 million years ago in Alberta, about 8 million years earlier than Ankylosaurus, was 6-7 meters long and weighed around 2-3 tons, about the same weight of the neighboring ceratopsids (Centrosaurus, Styracosaurus, Chasmosaurus etc.), but noticeably smaller than the more recent Ankylosaurus. note . Like Ankylosaurus, it too had armor plates arranged in rows along its back; but Euoplocephalus' armor was traditionally thought to be awesomely more complex, and may even be described as "artistic". A couple of flat bumps were on the neck, and two pointed spikes protruded from the shoulders. Several other spikes were placed in regular, elegant lines along its back. Even the elbows had three small round scutes each. The head was similar to Ankylosaurus, with mosaic-like scutes on its roof, four small horns in its corners, and bony eyelids. Finally, the club was trefoil-shaped and almost resembled the club of French playing cards. Some older drawings of Euoplocephalus show it with spikes sticking out from its tail club; this is based on an outdated interpretation of its relative Scolosaurus, see just below. Rooter, from The Land Before Time, is probably the most famous example of this.

A really cool animal to draw, anyway, whatever the name: in fact, Euoplocephalus/Scolosaurus appears as the actual stock ankylosaur in many dinosaur books. It's also worth noting that several alleged Ankylosaurus seen in books, documentaries and films tend to have some euoplocephalic traits, with conical horns instead of triangular, trefoil clubs instead of oval, and sometimes even the elbow scutes and the flat bumps on the neck. Despite this, Euoplocephalus and Scolosaurus are typically not portrayed in CGI documentaries, which will prefer their gigantic cousin — the fact that Ankylosaurus could fight T. rex while "Euply" and "Scolo" only had albertosaurs etc. to battle doesn’t help. Some dino-books wrongly portray Scolosaurus/Euoplocephalus living and fighting against Tyrannosaurus rex, which actually lived later.

Late Cretaceous North America has several example 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; the ceratopsid Monoclonius is today thought by several experts as a non-diagnostic juvenile centrosaur; and the small deinonychosaur Stenonychosaurus has been synonimized with Troodon since the 1980s. All this to not mentioning the notorious " Trachodon" case. The original specimen of Euoplocephalus was discovered in 1902, but between 1923 and 1929 three other genera very similar to it (Dyoplosaurus, Scolosaurus, and 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 

Scolosaurus is known from one really well-preserved skeleton from Alberta and several more incomplete specimens from Montana which had previously been given their own genus, Oohkotokia, after their initial stint as "Euoplocephalus". It was about the same size as Euoplocephalus, live in the same age, had a similar head but with longer, more swept-back horns, and a club also similar in shape. The main point is: the famous armor of Euoplocephalus made of differently-shaped plates has been found to actually pertain to Scolosaurus, while the real Euoplocephalus had less complex armor. The classic "Euoplocephalus" portrayals of the 1980s and 1990s are actually based on the aforementioned well-preserved Scolosaurus found in Alberta. This skeleton, nonetheless, lacked the skull as well as the clubbed tip of its tail, making its tail look shorter and ending with a single pair of spikes, which were actually in the middle of the tail.

Several old books and models have portrayed the resulting "stegosaur-tailed ankylosaur", wrongly showing it with much more generic armor than the Real Life 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 Gorgosaurus. Though few noticed, even 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.

  1. Entry Time: 1940s
  2. Trope Maker: Zdenek Burian's painting

Changes in Look: Polacanthus & Nodosaurus *

Some decades later the discover 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 Early Cretaceous, Polacanthus was rather small compared to Ankylosaurus or Euoplocephalus being 4 m/16 ft long, and its first original remain found in the isle of Wight was very incomplete. This explains why in older depictions Polacanthus had very light armor, consisting only of pairs of long dorsal spikes (hence the name, "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 whose it's the prototype. 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 Planet of the Dinosaurs and the film adaptation of The Land That Time Forgot. The animal has also a more prominent role in the puppet-series Dinosaurs as Robbie Sinclair's friend Spike, omonymous with the Stegosaurus non-talking puppy of The Land Before Time franchise.

Today, thanks to a much more complete specimen found in the early 1990s again in England, we know Polacanthus had an armor that was more extensive and Ankylosaurus-like, though even spikier. The lack of the club and the absence of the thagomizer were proven true. The polacanth appears with this new look in Walking with Dinosaurs as a follower of Iguanodon herds, as well as in most updated portraits in dino-books.

A notable change in appearence has also involved the official prototype of the club-lacking ankylosaurians, Nodosaurus textilis. This was the first ankylosaur discovered in the USA from remains that are more than simple teeth, during the Bone Wars, but still after Polacanthus. "Palaeoscincus" is known from isolated teeth found in USA before Nodosaurus, and has been treated as a wastebasket taxon since that for undetermined ankylosaur remains. The clubbed Ankylosaurus and Euoplocephalus were both found later than Polacanthus and Nodosaurus, in the early 1900 in Alberta, Canada.

Nodosaurus ("tubercled lizard") was bigger than the Polacanthus, but smaller than Ankylosaurus proper — about the size of the euoplocephalus. Curiosly, like what happens sometimes to Ankylosaurus, in classic portrayals Nodosaurus is shown with a simple armor lacking any spike. Why? Because the specimen found by Marsh was devoid of them; in reality, like all Nodosaurids, it had arguably long spikes protruding from both sides of the body. Obviously we don't know how long these spike were.

A strange-looking Nodosaurus appears in the first sequel of The Land Before Time movie as one of the three villainous young dinosaurs, aptly named "Nod", together with two equally unrealistic companions, a Hypsilophodon named "Hyp" and a Muttaburrasaurus called "Mutt" (both ornithopods). The nodosaur is also frequently shown in classic dinosaur books because of its historical prestige — usually with the traditional incorrect spikeless shape.

  1. Entry Time: 1978 (Polacanthus); 1995 (Nodosaurus)
  2. Trope Maker: Planet of the Dinosaurs (Polacanthus); The Land Before Time (Nodosaurus)

Young Struggling Dinosaurs: Pinacosaurus *

Many ankylosaurs are known from Asia. Pinacosaurus ("table lizard"), the most common in fossil record, was basically the equivalent of Euoplocephalus/Scolosaurus. Slightly smaller than them and with a much simpler armor than Scolosaurus, Pinacosaurus had also a narrower head, a hooked bill, different "horns", and a two-lobed club; it has traditionally regarded as one of the smallest clubbed ankylosaurs, but weighed nonetheless 1 ton or more, like a rhino. The bigger but less-common Tarchia and Saichania were more similar to Ankylosaurus; the mid-sized Talarurus was unusual, being barrel-shaped and short-limbed.

First found in 1920s, Pinacosaurus has been the first armored dinosaur found in Asia, by the same expedition led by Roy C. Andrews that first found Velociraptor, Protoceratops, Oviraptor, an the latter's eggs. Pinacosaur remains found later in the 1950s were wrongly labeled "Syrmosaurus". In 1988, Pinacosaurus contributed to fuel the Dinosaur Renaissance, by giving a proof of social behavior among juvenile dinosaurs: several youngsters were found dead together in a small area, maybe buried in a sandstorm. This discover, made by a conjunct Chinese/Canadian expedition led by Dale Russell, Dong Zhiming and Philip Currie, also showed that ankylosaurians were not necessarily loners as traditionally thought.

Pinacosaurus has appeared in speculative documentaries or mockumentaries about dinosaurs, even though usually unnamed — or at least, generically called "ankylosaur". Examples include Planet of Dinosaurs, "The Research of the Dragon", and The Truth About Killer Dinosaurs. The first two mention it because of the finding of the juveniles dead together: the third, more prosaically, to give a prey to Velociraptor, just like what happens to Protoceratops. Being the adult Pinacosaurus 15 ft long, far bigger than the 6 ft long Protoceratops, the programers chose a juvenile pinacosaur for the "raptor"'s meal. In the show, the dromeosaur kills Pinacosaurus by cutting its throat with its sickle-claw after a hard battle.

  1. Entry Time: 1990s
  2. Trope Maker: Portrayals set in Cretaceous Mongolia (the Velociraptor 's land)

A Sculpture in the Crystal Palace: Hylaeosaurus *

Huge Ankylosaurus has not always been THE ankylosaur. Was discovered at the beginning of the XX century, but several relatives were already known. They were simply smaller, less-armored, and above all, very fragmentary, and in the XIX were classified among the Stegosaurs. As a group, the Ankylosauria were recognized distinct only after Ankylosaurus. It's interesting that one of the three inspirers of the name “dinosaur” was just an ankylosaur: Hylaeosaurus ("lizard of the forest").

Discovered in England in 1840 by Gideon Mantell after his more famed dinosaur Iguanodon (and after Buckland's Megalosaurus as well), Hylaeosaurus was only 4 m long, less-than-half an Ankylosaurus, the size of Polacanthus. In famous Crystal Palace Park in London made in 1852 by Benjamin W. Hawkings the Hylaeosaur shows up with the Megalosaur and Iguanodont, and depicted larger than was in Real Life. Unlike the other two "original stock dinosaurs", it has remained quadrupedal after 160 years of dino-history. But this doesn't mean it's more accurate at all: our Hylaeosaurus was sculpted like a giant, armor-less iguana with a lizard-head and long tail, like a simple smaller version of the Crystal Palace Iguanodon and Megalosaurus.

Hylaeosaurus get usually mentioned together with its two companions when the "Crystal Palace" dinosaur sculptures are portrayed in media. In John Sibbick's famous Great Dinosaur Encyclopedia (published in year 1985) Hylaeosaurus is shown more correctly with a complex armor with sidewards-pointing spikes: once considere a nodosaurid because of its lack of club, it is today thought by some closerly-related with Polacanthus. Curiously the Polacanthus looks very different than Hylaeosaurus in the same book, showing a much simpler armor: this because the polacanth's "modern" look popularized by Walking With Dinosaurs emerged only in 1994, a decade later than Sibbick's work.

  1. Entry Time: 1854
  2. Trope Maker: Crystal Palace Park

The Unfair Sex: Sauropelta, Edmontonia & Gastonia *

Several dinosaurs have received a latin name ending with the unusual feminine suffixes -a or -ia: this is true expecially for ankylosaurians, but also for many other dinosaur pedsubgroup — sauropods like Jobaria, theropods like Nedcolbertia, stegosaurians like Miragaia, basal ornithischians like Trinisaura, and, more famously, the egg-caring hadrosaur Maiasaura. Among the ankylosaurians ending in -a the most well-known have probably been Sauropelta, Edmontonia, and Gastonia, all Cretaceous, North-American and clubless.

Gastonia (named after a human surname) was a middle-sized 4.5 m long ankylosaur from Early Cretaceous, smaller than the 7 m long Late Cretaceous Edmontonia and the even larger (7.5 m) but equally Early Cretaceous Sauropelta. Generally, clubless ankylosaurians were smaller compared with the clubbed ankylosaurids. Discovered in 1998 in Utah, several decades after the other two, the gastonia was related with the european Polacanthus, and shared with it the same spiky body and tail and the hip-scute. The edmontonia and sauropelta were more related with Nodosaurus, with long shoulder-spines, absence of the scute above the hip, and tails lacking long spikes.

Edmontonia had a pair of often double-pointed shoulder-spikes pointing forwards like horns, and was able to deliver fatal wounds with them when it charged like a rhino or a hippo against predators like the tyrannosaurs like Albertosaurus. Sauropelta too had a pair of huge spikes on its shoulders, pointing more upwards and not double-pointed but equally threatening, this time against big allosauroids like Acrocanthosaurus (tyrannosaurids still didn't exist at the sauropelta's times).

Gastonia has recently become popular in paleo-media, both because its armor was expecially spiky and impenetrable among ankylosaurians, and because lived just alongside the famous "giant raptor" Utahraptor — both dinosaurs were found in the same geological formation. It's easy to imagine that someone ultimately made them fighting against each other in a show, like a more ancient version of Tyrannosaurus vs Ankylosaurus, Albertosaurus vs Euoplocephalus, or Velociraptor vs Pinacosaurus. In the show, the ankylosaur Gastonia is portrayed rather accurately: it finally wins the fight by using its stingy tail to hit the dromeosaur to death, just like what the Ankylosaurus did with its club-tail against the T. rex in the earlier documentary Walking With Dinosaurs.

  1. Entry Time: 2008 (Gastonia), 2009 (Sauropelta), 2011 (Edmontonia)
  2. Trope Maker: speculative documentaries

The Earliest Tank: Scelidosaurus *

When we think about armor-bodied dinosaurs, our minds comes automatically to Stegosaurus. But let’s not forget Scelidosaurus: a very primitive thyreophoran from Early Jurassic, discovered in Europe and possibly North America. If the latter is true it could have met the famous double-crested carnivore Dilophosaurus in life. Some thought Scelidosaurus lived also in Asia, but this is not proven.

4 m long, half the length of an average Stegosaurus and small also for ankylosaurian standards, the scelidosaur was traditionally considered in the middle between stegosaurs and ankylosaurs, but some have recently suggested that it's the first true ankylosaur. Still, Scelidosaurus was more slender and less-heavy, and far less armored than traditionally-indended ankylosaurs. Its armor was made only of small bony tubercles sparse in regular lines along its body, limbs, and tail, while its small head had not a bony “cap” but just three short spikes on each rear-corner. Its jaws were typically ornithischian, but with the primitive frontal teeth on the upper one, like the pachycephalosaurs and Hypsilophodon. Its limbs were robust but agile (Scelidosaurus means "limb lizard"), more similar in shape to bipedal ornithischians than to stegosaurs or evolved ankylosaurs, even though some old portraits wrongly show it with stocky limbs similarly to the more advanced thyreophorans. Some scientists have hypothesized it was able to rear up on its hindlegs to reach higher vegetation, like the stegosaurs, but unlike the younger ankylosaurians, too heavily-armored to do so.

Scelidosaurus is not only a very early animal: it was also a very early find among dinosaurs in general. Its first skeleton is known since the XIX century even before Stegosaurus and Ankylosaurus have been known to science - but was described later than the Mantell's Hylaeosaurus, by Richard Owen. Like most of the others earliest dino-discoveries it was found in Europe (in Southern England), and reconstructing correctly its body was a long hard task. Having a not-so-impressive appearance Scelidosaurus has remained a little-stock animal. However, basal dinosaurs from Triassic and Early Jurassic often make paleontologists happier than their Late Jurassic or Cretaceous ones, because the most ancient dinosaurs help to understand a lot the affinities among the main dinosaurian groups, enhancing the reconstruction of their evolution.

  1. Entry Time: undetermined
  2. Trope Maker: Its status as "the earliest armored dinosaur"

Other ankylosaurians

Sorry, these aren't here. If you're looking for Borealopelta, Panoplosaurus, Dracopelta Acanthopholis, Saichania, Struthiosaurus, Gargoyleosaurus, Talarurus, Minmi, Antarctopelta, Tianchisaurus, and others, see here.

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Armor-headed Plant-Eaters

The most recent group of ornithischian dinosaurs, marginocephalians have been usually discovered in Late Cretaceous terrains. They were closer to ornithopods (see further) than to thyreophorans (see previous), and are divided in two very different subgroups: ceratopsians and pachycephalosaurs, unified by their armored head. The former can furtherly be divided in the more evolved Ceratopsids and their more primitive predecessors.

    Ceratopsians 

The ceratopsians were a group of dinosaurs characterized by a bony "frill" at the back of the neck. Starting as small bipedal animals like all the main dinosaur groups, they evolved towards a heavy quadrupedal body plan, while lengthening the frill and growing horns on their eyebrows and nose. Even though ceratopsians had erect limbs like every other quadrupedal dinosaur, some portrayals have shown them with splayed frontal legs. Moreover, their legs tend to be shown stockier and more "elephantine" than in Real Life.

The ceratopsid family contains all the largest members of the group. Apart from the frill shape and number/length of the horns, ceratopsids shared the same basic look. They are classically divided in two subgroups: those with long frontal horns, short nasal horn and (usually) long frills; and those with short frill, no frontal horns, and (usually) a long nasal horn. Triceratops, Torosaurus, Chasmosaurus and Pentaceratops are member of the first subgroup, while Styracosaurus, Centrosaurus/"Monoclonius", and Pachyrhinosaurus belong to the second one.

Protoceratops and Psittacosaurus have been the prototypical ancestral ceratopsians. They were much smaller than the proper ceratopsids, being not bigger than a human — in vivid contrast with their rhino-sized or elephant-sized cousins.

The T. Rex's Greatest Rival: Triceratops ***

https://static.tvtropes.org/pmwiki/pub/images/triceratops_-_copia_1219.jpeg

Lived 68 to 66 million years ago in Late Cretaceous North America. It 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 bisons lived in the Cenozoic (the dating of rocks was still inaccurate at the time). Its name means "three-horned face" and is due to its most prominent feature. It was about 26-29.5 ft/7.9-9 m long and weighing about 6-12 metric tons, and was one of the biggest ornithischian dinosaurs (only some hadrosaurs were larger). Hundreds of skulls are known so far, but amazingly not a complete skeleton. Two main species are recognized today: the larger Triceratops horridus and the smaller Triceratops prorsus, even though up to 15 species were described at one point due to the great variability of the skull. The novel Jurassic Park mentions "Triceratops serratus"; other species, like "Triceratops hatcheri", have been classified in other genera.

Triceratops has traditionally been considered the largest ceratopsian; its size and abundance in the fossil record have contributed to making it the most popular one. It has always been beloved by dino-fans. Maybe because with its short tail, big head, and rhino-like body, it has matched the image of a big herbivorous mammal more than the other stock dinosaurs, to the point we have a trope about this. But maybe, it's only its historical reputation as "the only plant-eater able to defeat the Big Bad Tyrannosaurus rex" — even though ankylosaurs and maybe even the biggest hadrosaurs might also have been able to defeat the tyrannosaur in a fight. Its portrayal in the movie Jurassic Park of 1993 consolidated Triceratops' popularity even more: the touching scene of the sick triceratops with the caring humans around has remained in public consciousness (the 1990 novel has Stegosaurus in this role), not to mention the strong temper of young character Cera of The Land Before Time series started in 1988. In older films, "Trike" tend often to be portrayed more like a Prehistoric Monster, like in Harryhausen's One Million B.C.

Compared to other stock dinosaurs, Triceratops and its relatives have been portrayed fairly accurately. The ceratopsids in the original movie The Lost World (the Trope Maker, from year 1925) are nearly as realistic as those seen in the 1999 docu Walking with Dinosaurs, which are actually Torosaurus (see below). Thanks to their obvious resemblance to rhinos, media Triceratopses have usually been portrayed as agile and active like a modern ungulate mammal; the main mistake in older depictions, other than the aforementioned issue regarding the legs, is the wide lizard-like mouth without the typical ornithischian cheeks. For a brief period, it was considered that triceratops was covered in quill-like bristles like their earlier relative Psittacosaurus, citing what appeared to be broken off nubs in skin impressions of the animal's back. However, these are far more likely to be osteoderms (bony scutes), like those of an alligator. Nonetheless, portrayals of bristly ceratopsids have become common since then in paleo-illustrations. Because of this belief some described horned dinosaurs as prehistoric boars, other than the more classic comparisons with rhinos and buffalos.

Triceratops and T. rex have been shown fighting in modern works from the first dino-movies and through the whole paleoartistic tradition (including one especially iconic painting). In these battles, the percentages of victories between the tyrannosaur and the triceratops appears to about 50%. Though all this may even be Truth in Television, it's likely that the tyrannosaur preferred younger and more vulnerable prey than an adult Triceratops. Often considered the badass guy of the plant-eating dinos, writers can’t resist the urge to make Triceratopses act like rhinos or bulls. They’ll be ill-tempered, will charge everything, and may even moo like bovines. Another classic in paleo-art is showing ceratopsids defending their young by making a barrier around them with their horns and frills pointed against the tyrannosaurids who aim to prey over their offspring, just like musk-oxen actually do against wolves when attacked, or even like what American pioneers did with their carriages against their enemies: this is a possibility, though not proven, made at the time of the "dinosaur renaissance" (late 1900 century).

The ceratopsids’ horn structure was more like cattle’s than to a rhino’s: that is, bony protrusions covered with a horny sheath. Their function is still debated: ceratopsian horns may have simply been display devices. The frequently-seen "Triceratops goring to death a big carnivore" scene might not be realistic, and some think the frontal horns were too fragile and not pointed enough to go through flesh. On the other hand, given the keratinous sheath would have made the horn less likely to break and helped better shape it, goring may still be plausible. Another classic hypothesis is that triceratopses locked their horns like deer in head-vs-head combats, based on possible "wounds" found in ceratopsian skulls. However, only some Triceratops specimens show curved frontal horns apt for that, others had straight horns. The frill was variable, too: some individuals had tubercles on its edges, while others had smooth shields. Generally, most media Triceratopses have tubercled frills.

The parrot-like jaws are rarely mentioned, to the point that some authors omit the shape from their models to make Triceratops more like a rhino or a bull, again falling in Temper-Ceratops. Some have gone even further, showing ceratopsians with sharp carnivorous teeth even in the tips of their jaws, especially common in some rubber toy collections. In Real Life, the ceratopsians' jaws were the strongest among all plant-eating dinosaurs, filled with sharp cutting teeth behind the parrot bill, but were arguably adapted to eat fibrous plants, not tear meat — or at least this was not the main function. Some thought the powerful maxillary muscles were anchored to the frill, but this is not proven. Even less mentioned are the pair of bony knobs near the cheeks; they may have been for protecting the head furthermorely, or they may have been only for display.

  1. Entry Time: 1925
  2. Trope Maker: The Lost World (film)

Crowned Head: Styracosaurus **

https://static.tvtropes.org/pmwiki/pub/images/styracosaurus_-_copia_6991.jpeg

Several genera of horned dinosaurs other than Triceratops existed in Late Cretaceous North America, but only some of them have made appearances in pop culture, and Styracosaurus is the only one to do so with regularity, sometimes as substitute for Triceratops, other times together with it. Being more spectacular but less common in the fossil record than other ceratopsids like Centrosaurus or Pachyrhinosaurus, this makes it the usual Rule of Cool example.

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 Cretaceous dinosaurs were actually described during this "rush", but only the coolest-looking ones joined the stock dinosaur ensemble. About half as long as a 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. Styracosaurus had also shorter and stronger jaws than Triceratops. Some speculate it was more sociable than triceratopses and lived in more numerous herds.

Styracosaurus' frill spikes were not true horns as commonly said, but only an Up to Eleven 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 Dinosaurs) 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. Interesting than another modern species of lizard, the Jackson's chamaeleon of Africa, has three horns and a frill very reminescent of Triceratops, and the cowl of the australian frilled lizard resembles a bit a triceratops shield when open.

Why did ceratopsids have the frill? The bony core has a pair of large holes that make it less heavy but also less useful as protection (Triceratops was an exception, having a solid frill without holes). The frill could have been raised for threat display. Another hypothesis is that it was a thermoregulating device: like Stegosaurus' plates, ceratopsians' shield seems to have been rich in blood vessels. Maybe the frill was for making the several ceratopsid species more distinctive, like the hadrosaur crests. It is also possible that frills show sexual dimorphism.

The styracosaur has appeared in several works since the first portrayal in 1933 (in The Son of Kong), and is also a common feature in toys and popular books. On the other hand, recent documentaries haven't represented it so frequently. Maybe because in Real Life Styracosaurus could not battle Tyrannosaurus rex as Triceratops did, but only smaller carnivores like Daspletosaurus.

  1. Entry Time: 1933
  2. Trope Maker: The Son of Kong

The Biggest Skulls: Torosaurus & Pentaceratops *

Torosaurus latus was mainly made famous by Walking with Dinosaurs in 1999, where is portrayed as the main ceratopsian in the show (Triceratops appear only in form of a carcass). But well before 1999 Torosaurus was already known among dino-enthusiasts because of its huge skull, long believed the biggest among every land-animal that ever existed — 8-9 ft long, taller than an adult person if put vertically. When its huge frill was automatically raised up by lowering the main head, the shield could have been used as a scaring device against predators and rivals, making the animal looking bigger that it actually was if seen from the front. According to some, the choice to give to Torosaurus the main role instead of Triceratops is just because of its bigger frill.

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

Recently, some scientists have speculated that Torosaurus may not have been its own species 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 few years after the name Triceratops, would be retired and Triceratops would remain in use. However, 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.

Despite many of the most well-known ceratopsian genuses had the usual “saurus” ending (not only Torosaurus and Styracosaurus but also Centrosaurus, Pachyrhinosaurus, Chasmosaurus and others), most described kinds have the same suffix of the Great-Stock member. -ceratopses do abund here: after Triceratops (“three horned face”) and Protoceratops (“first horned face”, because was a ceratopsid predecessor), the most well-known is Pentaceratops (“five-horned face”). But did it really had five horns? Well… no. They were only three. The other two “horns” actually were simple protrusions arising from each cheekbone - a common ceratopsian trait, but particularly evident in Pentaceratops. One of the classic long-frilled ceratopsids, Pentaceratops looked pratically like the intermediate form between Torosaurus and Chasmosaurus: smaller than Torosaurus but bigger than Chasmosaurus, lived before the former but after the latter. Its horns were shorter than Torosaurus but more developed than many Chasmosauruses. Its frill was neither elliptical / smooth like the Toro’s one, nor triangular / complex like the Chasmo’s: it was rectangular, and lightly serrated around its whole perimeter like that of many Triceratopses. The frill-opening of the "penta" were very wide like those of chasmosaurs, contrary to the smaller ones of Torosaurus.

Known since the first half of the XX century from remains discovered in Texas, 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 2.5 m long skull, used to bear the record for “the biggest-headed land animal ever”; this putative pentaceratops’ skull was 3 m long. Science Has Marched On however, and this specimen has been deemed a separate animal in January 2011, meaningfully-named Titanoceratops. Pentaceratops has apperared in the videogame Jurassic World as one of the cloned dinosaurs in the park.

  1. Entry Time: 1999 (Torosaurus); 2018 (Pentaceratops)
  2. Trope Maker: Walking with Dinosaurs (Torosaurus); Jurassic World videogame (Pentaceratops)

Immense Herds: Centrosaurus & "Monoclonius" *

If you think Triceratops was the ultimate rhino-dino, is only because you have never heard about Centrosaurus. Like Styracosaurus, the latter had a look that literally resembled a rhinoceros. Its nasal horn was much longer compared to Triceratops, and maybe was used in the same way of a modern black rhino - for obvious reasons, this cannot be verified. While the usual frontal horns were mere hints on Centrosaurus, renforcing even more the rhino-resemblance. About the frill, it was rather short, undulating-edged, with that pair of bony openings covered with skin in the living animal, present in most ceratopsian outside Triceratops and few others. But the most unexpected thing is a pair of bony “hooks” curving downwards from the top of the shield; for some unexplicable reason they are often taken out in Centrosaurus models or drawings. Its name, "pointed lizard", do refer to these hooks and not to its long nasal horn as one could expect. The full name is Centrosaurus apertus ("apertus" = open, a reference to the frill-holes).

Named in the beginning of the XX century, most of its remains were then attributed to another relative, “Monoclonius”, which has long been the archetypical “unicorn-dinosaur” in books and documentaries. Then, a spectacular find was made in Alberta in year 1980: a whole graveyard of about 500 Centrosauruses died together, probably killed while trying to cross a river in flood. This discovery was one of the first concrete evidence of migrating behaviour in dinosaurs, a bit like modern caribous and wildebeest which also sometimes die in group during their river-crossings. Since then, Centrosaurus has mainly replaced “Monoclonius” in books/docus as “the one-horned ceratopsid”.

Another centrosaur graveyard even bigger by number of specimens was found around 2010 in Alberta, and is believed today by many the biggest dinosaurian bonebed of the whole world, named the Hilda mega-bonebed. Curiously, the centrosaur was unnecessarily renamed "Eucentrosaurus" in year 1988, but returned Centrosaurus again soon after. It should not be confused with the small stegosaur Kentrosaurus, which was Jurassic (70 my earlier) and only half the bulk of it. To avoid the confusion, one can pronunce them differently: "sEn-trO-SAURus" the ceratopsian, and "kEn-trO-SAURus" the stegosaur.

About “Monoclonius”, this one has been a very early discover, made in the XIX century during the Bone-Wars, but now is regarded by many as the juvenile-stage of Centrosaurus and its relatives. If so, then “Centrosaurus” would become invalid, because "Monoclonius" was the first name created. "Monoclonius" (which doesn't mean "kone horn" as sometimes said, but "one sprout") was slightly smaller than Centrosaurus but with the same rhinoceros-like appearence: long nose-horn and no real front-horns, but its frill had not the famous downwarding "hooks" of Centrosaurus or it had them much shorter. While Triceratops was officially described by Marsh, "Monoclonius" was one of the few prominent bone-war dinosaurs first-described by Cope. Unlike alot of other "stock obscure" dinosaurs (the ones signed with one single star here to be clear), Monoclonius has a notable appearance in popular culture: Prehistoric Beast by Phil Tippett, who would go on to be a supervisor and consultant for the Jurassic Park films.

  1. Entry Time: 1978 (Centrosaurus); 1984 (Monoclonius)
  2. Trope Maker: Planet of the Dinosaurs (Centrosaurus); Prehistoric Beast (Monoclonius)

Triangle-Shield and Thick-Nose: Chasmosaurus & Pachyrhinosaurus *

Maths are not always a exclusively-nerd thing. It can also be amusing, expecially when you can apply it to dinosaurs. Chasmosaurus ("chasma" = opening, ravine, fenditure in greek) can just be recognized by the geometry of its frill: strikingly angular in shape, if seen frontally almost seemed a reversed Isosceles Triangle with the base on the top and the apex attached to the skull. Its edge was also complex: smooth and V-shaped at the “hypothenusa”, spiky on the two upper corners, and half-smooth / half-undulating on the two “cathetes”. Moreover, this frill was also very elongated, almost like the Torosaurus and Pentaceratops ones, and was arguably used for the same purpose. But Chasmosaurus could also have used the two acute point of its shield to scare or harm predators or rivals, like what Styracosaurus, Centrosaurus and Pachyrhinosaurus could have done with their frill-spikes — a task that the smoother-frilled Torosaurus, Triceratops and Protoceratops were unable to do. Such spiny headcrests could be confronted with deer and moose antlers, also used as weapons against predators or competitor males.

Compensating this, the remaining head of the chasmosaur was less spectacular than the torosaur's and triceratops's one: the horns were three like Triceratops, but were rather short in comparison – some individuals had mere hints of the frontal ones; classic hypotheses say they’re from females and/or distinct species. The snout was rather long and narrow compared with that of Styracosaurus and Centrosaurus.

Known since the 1910s, Chasmosaurus is one of the most common ceratopsids in fossil record, and is often considered the prototype of the usually long-shielded subgroup: the Chasmosaurines or Ceratopsines, which includes also Triceratops, Torosaurus and Pentaceratops. However, the genus Chasmosaurus has been recently split in several new genera, in year 2010. In Fictionland, the chasmosaur was portrayed in a bunch of old movies, and some modern-cartoon "Triceratops" have a suspiciously Chasmosaurus-like triangular frill. Also worthy of note is the docu Planet Dinosaur, which shows also a huge herd of Centrosaurus dying in a flood.

Ceratopsids are classically known as “horned dinosaurs”: but this one seems not to have liked our definition. Pachyrhinosaurus (“thick-nosed lizard”), at a first glance, resembles more an oversized Protoceratops than a Triceratops: it has no true horns on its skull, it had a thickened boss upon its nose, often described as similar to a lunar crater, and smaller bosses over its eyes. To compensate, its short frill has an elaborate shape, with two horn-like spikes protruding from its rear-corners, other minor undulations elsewhere, and a small prominence pointing upwards from the center of the shield, analogue to the pair of "hooks" of Centrosaurus.

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 it is a true ceratopsid, more precisely a Centrosaurine - that is, a relative of Centrosaurus and Styracosaurus. It was recently shown that Pachyrhinosaurus was the largest and the last surviving Centrosaurine, living at the same time as T. rex and Triceratops, though much farther north. The biggest species of pachyrhino was larger than the other species of its ceratopsid subfamily, but didn't reach the size of a Triceratops or a Torosaurus fully grown.

Before the nineties Pachyrhinosaurus was one of the rarest ceratopsids in fossils: then, in the 1990s, a whole herd was discovered in Alaska. Since other Pachyrhinosaurus remains have been found much souther, this might be another proof of migrating behavior among horned dinosaurs. Pachyrhinosaurus should never get confounded with Pachycephalosaurus: both had something “thick” in their skull, but in the latter’s case was the head, not the nose. Some could nickname this ceratopsian "the other pachy". The Turn of the Millennium saw for some reason a sudden increase in Pachyrhinosaurus's appearances in pop culture, starting as a background character in Dinosaur, and then beginning a major character in the eighth Land Before Time film, and in a starring role of the Walking with Dinosaurs film. Maybe its oddiness among the "classic" ceratopsids has contributed to this formerly-unexpected success.

  1. Entry Time: 1970 (Chasmosaurus); 2000 (Pachyrhinosaurus)
  2. Trope Maker: When Dinosaurs Ruled the Earth (Chasmosaurus); Dinosaur (Pachyrhinosaurus)

The First-found Dinosaur Eggs?: Protoceratops **

https://static.tvtropes.org/pmwiki/pub/images/protoceratops_-_copia_1232.jpeg

Protoceratops lived 75—71 million years ago in Late Cretaceous Asia, unlike the giant ceratopsids, which were almost-exclusively North American in distribution. 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".

The most commonly known species of Protoceratops is P. andrewsi (from Roy Chapman Andrews); another found more recently is P. hellenikorhinus (the second word means "greek nose"). At a first glance, Protoceratops resembled a miniaturized ceratopsid like Triceratops: four-legged, with the same robust body, short tail, and unmistakeably ceratopsian head. However, it differed from ceratopsids mainly in having no true horns. Other differences include: a simpler frill lacking protuberances (but with the same pair of holes to make it lighter); bigger/thicker cheek-spikes; stronger parrot-jaws that almost look compensating the lack of horns; and legs more adapted to running, looking more like those of an ornithopod than those of a ceratopsid (even though incorrectly pillar-limbed protoceratopses are a common sight in media). The genders might have been sexually dimorphic: larger skulls with a nasal bump and a couple of upper "canine teeth" probably belonged to males — arguably with the purpose to attract females like deer's antlers and boar's tusks.

First discovered in Mongolia in 1922, Protoceratops has always been one of the most abundant Asian dinosaurs in fossil record, with hundreds of specimens discovered so far — earning it the nickname "the sheep of the Cretaceous". Given the large numbers of animals found together, they probably lived in herds like the bigger true ceratopsids. Many juveniles of the protoceratops have also been found, and its growth pattern is one of the best understood among nonbird dinosaurs.

Protoceratops was the most famous Asian dinosaur until Jurassic Park made Velociraptor famous. The discoverer of Protoceratops, Roy Chapman Andrews, was an U.S. scientist who fit the Adventurer Archaeologist trope so well, he could have been the real inspiration for Indiana Jones. He attributed to it some elongated eggs which now are known to belong to Oviraptor. These were the very first non-avian dinosaurian eggs ever identified. The original crushed Oviraptor skull was found nearby. A classic image in paleo-art is showing Protoceratops hatching its eggs and chasing or even trampling an egg-robbing Oviraptor. However, several nests complete with eggs were found later in Asia, which were actually laid by protoceratopses. Dinosaur eggshells were porose like those of modern birds to permit the embryos inside to breath: Protoceratops laid them in a circular manner, and it was once hyped that they were too many in a single nest to have bern laid by a single female — one of the first signals of group parental behavior, well before that of Maiasaura of The '80s, but without a concrete proof unlike the latter.

One especially spectacular find from 1971 consists of a Protoceratops and a Velociraptor clutched together: they were probably fighting each other when they were buried by a sudden sandstorm or a collapsing sand dune. It still remains the best evidence of a "dinosaur battle" between an herbivore and a carnivore even today. The Protoceratops appears to be biting the Velociraptor with its parrot-jaws, while the "raptor" is holding the protoceratops' head with its forelimbs and has one of its sickle-claws near the herbivore's throat. The real cause of the battle is uncertain, however: probably the protoceratops was defending itself and/or its offspring from the carnivore. But it's suspected by some that Protoceratops was the first attacker. It's possible that ceratopsians occasionally ate meat: if true, then maybe this "proto" was trying to eat the Velociraptor's eggs or chicks; and this would have provoked the reaction of the latter.

Despite its scientific relevance, because of its relatively modest appearance Protoceratops is less portrayed in pop-media than Triceratops and Styracosaurus. Perhaps the most well-known protoceratops is B.J., that yellow guy seen in Barney & Friends. In the much more beloved book series Dinotopia, the talking dino-character who befriends humans is a cute Protoceratops. This dinosaur appears also in many documentaries, either as a prey of Velociraptor or as the chosen victim of an egg-robbing Oviraptor, as the possible ancestor of Triceratops, or as an example of a particularly common dinosaur in the Cretaceous.

  1. Entry Time: 1940
  2. Trope Maker: Fantasia

The Parrot-Dinosaur: Psittacosaurus *

Together with Protoceratops, Psittacosaurus is by far the most important and well-known ceratopsid predecessor. At least, if you ask paleontologists and paleo-fans. Rule of Cool always wins in pop-culture, with small-sized dinosaurs usually with very few chances to get consideration by writers or film-makers - points minus when they are plant-eaters.

Digression closed, here we have many things to say about Psittacosaurus, definitively one of the most important dinosaurs. An Asian animal like Protoceratops it has classically been considered the most ancient ceratopsian ever (lived 100 million years ago, in the Early Cretaceous) and the forerunner of all the Late Cretaceous “neoceratopsians” (aka Proto+Horned). With its primitiveness, Psittacosaurus resembles anything but a Triceratops: small (6 ft long), relatively slender, with only hints of horns and frill, this dinosaur looks more to an ornithopod than to a ceratopsian externally (like its relatives, the pachycephalosaurs). Once thought to be capable of walking on all fours, detailed study of its forelimbs shows it was entirely bipedal. The main trait revealing its relationship with Triceratops and kin is the parrot-like upper bill made by an unique bone called "rostral bone", the anatomical hallmark of ceratopsians. The hook-bill gives it the name “Psittacosaurus”: “psittacos” is Greek for parrot. Another thing which ties Psittacosaurus with its horned descendants are the prominent bony “cheeks”, absent in all ornithopods but far less developed than those of a Protoceratops however. The shape of the psittacosaur short head, one of the shortest among all dinosaurs, with a big powerful beak, high orbits and nostrils, and no true frill or horns, makes the resemblance of its face with that of a modern macaw parrot very close.

Psittacosaurus was discovered in the 1920s in Mongolia together with Protoceratops. Its discovered was famed paleontologist Roy Chapman Andrews – a very adventure-loving guy, to the point he could have even been the inspiration for Indiana Jones as said above. Since then, psittacosaurs have been discovered everywhere in eastern Asia, from Siberia to China to Indochina, but recognized 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, just the same level of Protoceratops - individuals from all ages are known, and also several nests full of eggs. Our “parrot-dinosaur” also detains the record of the non-avian dinosaur with currently most species described: more than 10! The most classic one is P. mongoliensis, "Mongolian parrot-lizard".

In the 2000s, many new discoveries have furtherly raised its importance, making it perhaps the most scientifically well-known member in the whole non-bird dinosaur world. The main discovery has been made in Liaoning, where one specimen has preserved integument which shows porcupine-like quills raising upwards from its tail, for uncertain purpose (Defense? Mating?). These were the very first filamentous skin-structures ever found in an ornithischian dinosaur; this has changed our perception of bird-hipped dinosaurs, which were more similar to birds than previously thought. Indeed, a few scientists now argue those quills (or similar structures) could also be in all the other more evolved ceratopsians, Triceratops included, or at least in the protoceratopsians. Another unexpected discover made in year 2000 in the same site, did debunk the classic “Mesozoic mammals were underdogs ruled by dinos”: the cat-sized carnivorous mammal Repenomamus has been found with baby Psittacosaurus remains in its ribcage. In 2016, the "psittaco"'s scales were discovered to have preserved pigments in them, revealing it to be a countershaded dark brown on top and a lighter brown on the bottom, like a deer or an antelope. This resulted in modelers building what many news sites bragged to be the most accurate non-avian dinosaur model of all time.

  1. Entry Time: 2000s
  2. Trope Maker: the fossil discoveries from that period

Other ceratopsians

Sorry, these aren't here. If you're looking for Anchiceratops, Arrhinoceratops, Avaceratops, Bagaceratops, Chaoyangsaurus, Einiosaurus, Leptoceratops, Microceratus, Montanoceratops, Yinlong, Zuniceratops, and others, see here. And here.

    Pachycephalosaurians 

Unlike ceratopsians, pachycephalosaurians kept the original bipedal body plan, but evolved thick skull roofs and bony knobs on their heads for uncertain purpose. Like ceratopsians, there is the possibility that were omnivores. Needless to say, the iconic member of the group is also the biggest one, Pachycephalosaurus; smaller kinds include Stegoceras, Homalocephale, Prenocephale, Stygimoloch, and Dracorex (the latest two might be simple juveniles of Pachycephalosaurus).

My Brain Is Big: Pachycephalosaurus **

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Lived during the Late Cretaceous 70-66 million years ago in North America like many well-known dinosaurs. It usually shows up when an author feels like showing an "exotic" dinosaur. Its relationship with other dinosaurs has long been uncertain: originally classified as an ornithopod — originally, scientists tended to classify all ornithischians that were not stegosaurs, ankylosaurs, and ceratopsians in the ornithopod group: for example, the ceratopsian Psittacosaurus, the basal Heterodontosaurus and Lesothosaurus, and even the quadrupedal thyreophoran Scelidosaurus — its affinity with ceratopsians was demonstrated only in the 1980s.

Pachycephalosaurus (pronounced "pAcky-sEfalo-SAURus"; "-kEfalo-" is OK too) means "thick-headed lizard", and is by far the biggest known pachycephalosaur, but still small compared with most stock ornithischian dinosaurs. Its actual length is uncertain: popular books often set its size at up to 30 ft/9 m; a length of 15-18 ft/4.6-5.5 m is more likely. The other relatives were not 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 renamed Pachycephalosaurus only in 1943. No other parts of the body have been found since then: reconstructions are typically based on smaller pachycephalosaurians, expecially Stegoceras, the most complete pachy to date.

Pachycephalosaurus is distinguished by its dome-like head which makes it look very 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'. Its nickname "The Bone-headed Dino" is quite accurate. A number of bony knobs and blunt spikes around the base of the dome and on its nose contrasted with the smoothness of the dome to create a look of partial baldness or of a monk's tonsure, i.e. a "Roman tonsure"; hence the epithet "Friar Tuck-osaurus" in The Lost World: Jurassic Park film. These knobs and spikes were homologous to those of the head and frill of the ceratopsians.

Being totally bipedal, pachycephalosaurians were superficially similar to theropods, but their jaws and grinding posterior teeth were typically ornithischian, and thus plant-eating. However, Pachycephalosaurus had weaker jaws than ceratopsians or hadrosaurs and still retained small pointed teeth on the tips of its jaws which were lost in the more evolved bird-hipped dinosaurs; this would indicate the pachy had a mixed diet based on plant material with insects and small vertebrates as a supplement. Its relative Stegoceras shows small five-fingered forelimbs, a slender body, long tail, and running legs - perhaps less adapted to running than those of the similar-shaped "gazelle-dinosaur" Hypsilophodon. The body of Pachycephalosaurus probably was similar to Stegoceras, but the former being larger than the latter, its body might have had an overall stockier frame.

As one of the most recent groups of herbivores/omnivores in formal dinosaur classification, pachys never appear in the oldest works. The ur-example was the 1956 novel A Gun for a Dinosaur; one of the most popular ones was The Land Before Time in 1988, where the pachy shows up as a predatory villain trying to kill one of the protagonists with headbutts. The headbutting is a standard trait when pachycephalosaurs appear in works. Classic dino-books and documentaries from the Dinosaur Renaissance traditionally depicted males trying to impress females by ramming their heads into each other. Pachycephalosaurs have often been compared with rams: some scientists even hypothized they lived in mountain habitats just like the bighorn sheeps. This would explain their rarity in fossil record (mountains do not preserve fossils well). However, the mountain-living hypothesis is not much followed today, and pachycephalosaurian remains have been found mixed together with the other Late Cretaceous dinosaurs.

Scientists found in the 2000s that the smooth domes would have slipped if struck against each other, and proposed that pachycephalosaurians bashed each others' sides and hips instead. But even this has been disputed: recent studies seem to show their necks were weaker than traditionally thought, maybe not able to withstand such an impact. Now some scientists think pachycephalosaurs simply used their dome heads to display maturity like an oversized toucan bill. But even more recently, a 2013 study found healed injuries in multiple pachycephalosaur domes, suggesting that they were used for headbutting and/or flankbutting after all. The pachycephalosaurs' real lifestyle and diet will probably remain a mystery until more complete remains will be found.

The large Pachycephalosaurus was once the only "bonehead" portrayed in fiction. This changed in the 2000s when two smaller relatives, Stygimoloch spinifer and Dracorex hogwartsia (the latter discovered as recently as 2006) started making occasional appearances as well, thanks to their even spikier heads. A very recent theory (2009) suggests that these two horned pachys were just juvenile Pachycephalosaurus, but see below for these two.

  1. Entry Time: 1956
  2. Trope Maker: A Gun for a Dinosaur (novel)

The "Other Stego": Stegoceras *

Rule of Cool is merciless. It doesn’t matter if you are the most abundant, complete, well-known, or even the first discovered dinosaur within your group: if you aren’t cool enough, another cooler relative will take you the stock-role in pop-consciousness.

Stegoceras matches perfectly all this. By far the most abundant, complete, well-known, and even the first discovered dinosaur within its group, which should be renamed Stegocerases rather than Pachycephalosaurs. 2.5 m long, Stegoceras ("horned roof") was just half the length of Pachycephalosaurus, but shared the same Friar-Tuckish face, having a smooth dome bordered by a collar of tubercles. But its dome was less-prominent, “only” 1 inch thick, and its nose lacked those spikes Pachycephalosaurus had. In short, it appears like the milder version of Pachycephalosaurus. Its full scientific name is Stegoceras validum (validum = courageous).

Both pachys lived in Late Cretaceous North America, but the smaller one was slightly earlier, as usual among Late Cretaceous dinosaurs. Was discovered in year 1924, but originally thought a weird ornithopod (some even thought the bulge-head was a deformity due to illness); the placement in the current group was made just after the discover of Pachycephalosaurus twenty years later. Don’t confound it with Stegosaurus. As a pachy, “the other Stego” was a small, two-legged animal with a heavy head and the “body armor” limited to its skull.

The other Stego has also the distinction to be the only pachycephalosaur from which many individuals are known, not just one or two, and the only whose body-frame is known with completeness, to the point to be used as a model for other relatives: when you watch the body, legs, arms, neck and tail of a pachycephalosaur, you’re arguably watching those of Stegoceras. In dinosaur books, the other Stego is often treated as the effective stock pachycephalosaur, unlike TV programs which will prefer the namesake of the family.

For infos about its possible lifestyle, see Pachycephalosaurus above. Some alleged Stegoceras remains were once putatively announced in China, but don't pertain to it. Some have also speculated that the stegoceras was sexually-dimorphic, and one putatively feminine skull with a slightly less-thick skull-roof was once assigned to its own genus, "Ornatotholus" ("ornated dome").

  1. Entry Time: 1956
  2. Trope Maker: A Gun for a Dinosaur (indirectly)

Spiky Pachys: Stygimoloch & Dracorex *

Two North-American pachycephalosaurians have gained quite striking names: Stygimoloch spinifer and Dracorex hogwartsia. The former means "Spiky Devil from the Death River", the latter "Hogwarts' Dragon King".

Both lived in USA alongside Pachycephalosaurus and, like most pachys, are known only from one skull or little more. Stygimoloch was discovered in The '80s: Stegoceras-sized, is the only known pachycephalosaur with spikes developed into true horns, and its dome was tall and narrow (one former invalid synonym of it was "Stenotholus", "narrow head"). Meanwhile, Dracorex was found only in 2006: also of similar size, had an almost-as-spiky skull coupled this time with a flat head. Even though much more developed, the spiky ornamentation of both was very similar to Pachycephalosaurus. Basing on this detail, some have proposed in the 2000s that the “devil” and the “dragon” are just different immature stages of Pachycephalosaurus, with Dracorex being the most immature growth-stage, Stygimoloch the intermediate one, and Pachycephalosaurus the fully-mature form.

Stygimoloch recently had a memorable scene in Jurassic World: Fallen Kingdom; it's worthy to be noted that film consultant Jack Horner advised against featuring the Stygimoloch due to the above controversy, but was overruled by the filmmakers. Talking about Dracorex hogwartsia, our "harrypottersaur" is one of the few real dinosaurs portrayed in the TV series Primeval, even though in a quite fanciful way, with an actual dragon-like crest on its back.

  1. Entry Time: The 2000s
  2. Trope Maker: Disney's Dinosaur (Stygimoloch); Primeval (Dracorex)

Other pachycephalosaurians

Sorry, these aren't here. If you're looking for Homalocephale, Prenocephale, Goyocephale, Tylocephale, Gravitholus, Sphaerotholus, Wannanosaurus, Micropachycephalosaurus, Yaverlandia, and others, see here.

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Bipedal plant-eaters (usually)

The Ornithopod group contains several ornithischian dinosaurs of different size, from Middle Jurassic to Late Cretaceous. The smallest ones were slender and completely bipedal, and probably omnivorous. The more evolved ones became bigger and returned to a 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 theropods. Unlike the latter, they had small mouth openings and blunt teeth for grinding plant matter. Ornithopods are the most abundant dinosaurs in fossil record; even though they lacked the thick defenses of the ornithischians mentioned above, they made up for that with either speed or sheer bulk.

    Hadrosaurs 

Hadrosaurs are nicknamed "duck-billed dinosaurs" because of their wide, flat beaks especially evident in some species, less so in others. They all lived at the end of the Cretaceous. The biggest and most evolved ornithopods, their grinding maxillary mechanism was the most efficient of all reptiles ever, and they also developed complex prominences above their skulls with social functions.

A comparatively high number of hadrosaur species are portrayed in popular media: Parasaurolophus and Corythosaurus thanks to their evident headgears; Edmontosaurus (called Trachodon, Anatosaurus or "Anatotitan" in old media), because it's the most duck-billed duckbill, and one of the first described too; Maiasaura, which has heavily contributed to the Dinosaur Renaissance; and, more seldom, Saurolophus, Kritosaurus/Gryposaurus, Lambeosaurus, and the official prototype of the group, Hadrosaurus. Breaking the usual rule, none of them is the biggest known hadrosaur. Parasaurolophus and Edmontosaurus have always contended the record of the most iconic duckbill.

An Instrument For Trumpeting: Parasaurolophus **

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Lived 76 to 73 million years ago in Late Cretaceous North America. 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 whip-like, 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 other relatives. Its long, backwards-pointing protrusion made its skull a bit longer than an adult human’s height. Even though is often called a "horn", it was actually an extension of the nasal cavities, and ended in a blunt point. Of course, you can 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").

The hadrosaurs' lack of specific weapons has led to them being nicknamed "the Cretaceous Antelopes". They are usually shown in dino-books and documentaries as "chosen preys" for tyrannosaurs, "raptors", and giant crocodiles, incapable of offering resistence and obliged to flee away from them. This might be Truth in Television, but in Real Life "duckbills" were not exactly gazelle-like creatures. Adult hadrosaurs were strong and heavily-built: in a high-speed collision against a tyrannosaur, the hadrosaur had less of a chance of falling down and would've been able to get up more easily thanks to its longer forefeet. It's easier to imagine tyrannosaurs hunted young hadrosaurs more often than adults.

Like the sauropods, hadrosaurs used to be associated with water in pre-Renaissance times. Indeed, the sauropods and the hadrosaurians 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 substain their bulk on land, unlike the giant sauropods. 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 The Land Before Time).

Even after it was established that hadrosaurs were mainly terrestrial, scientists still said they were more skilled swimmers than most other dinosaurs and used to flee in water to escape the less able giant theropods. Recent research seem to indicate hadrosaurs were not particuarly accomplished swimmers in respect to other dinosaurs, or even that tyrannosaurs were more able to move in water than the "duck-bills" — of course, this cannot be verified.

Specifically regarding Parasaurolophus, countless hypotheses have been made about the function of its "horn": among them, a tool to thread its way through the dense forest foliage, or even a snorkel when swimming underwater. The latter just plain doesn't work; there aren't any holes on its tip. The most commonly-accepted scientific theory is that the complex series of tubes found within were used for amplifying calls like a sound box of an instrument. Scientists have even turned out to reproduce these calls, which quite resemble a brass instrument — Hilarious in Hindsight, this’d really make its crest like a "horn": the musical one. It's highly probable the headgear had also a display function: it might have been brightly colored to attract attention, and could have had a flap of skin stretched from it to the neck, but both hypotheses are unproved.

This dinosaur has appeared in almost every dino-film, but almost always in minor roles — basically with the sole purpose to increase the variety of the "dinosaur world". And don’t expect to hear its name, either — even though not one of the shortest dino-names, it remains cool-sounding anyway. A good example is in the Jurassic Park films. Some Parasaurolophuses are visible behind the Brachiosaurus in the famous "Welcome to Jurassic Park!" scene of the 1st 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’s Fantasia and Disney's Dinosaur. One rare example of a major-character Parasaurolophus is seen in The Land Before Time... at least, Ducky and her parents are officially labeled as such: they’re actually another hadrosaur, Saurolophus.

  1. Entry Time: 1940
  2. Trope Maker: Fantasia

Donald Duckosaur: The Edmontosaurus / Trachodon / Anatosaurus / "Anatotitan" Case **

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No other Stock Dinosaur has had such a Mind Screw story than the Edmontosaurines: the Brontosaurus/Apatosaurus is nothing in comparison. Here, Science Marches On is to a Up to Eleven degree, coupled with a huge Taxonomic Term Confusion and I Have Many Names. Edmontosaurines roamed North America at the very end of the Cretaceous, 73-66 mya. Two genera were recognized since The '90s, Anatotitan and Edmontosaurus, but they were reunited into one in 2011. Some claim this makes Edmontosaurus the only valid name for this dinosaur, while others support the separation of Anatosaurus. By any name, these creatures included both normal-sized species (10 m) but also some of the biggest hadrosaurian species, reaching 12/13 m long — as long as T. rex and a bit heavier than it. Despite this, their size didn't preclude them to be among the rex's favorite prey, though it more often attacked the young, sick, injured and dying than the healthy adults of the big-sized species.

Edmontosaurus is one of the most scientifically known dinosaurs. More than 10,000 known specimens (most other dinosaurs have less than 100 known specimens, but usually much fewer) show every evidence about its life, even diseases like cancer or fractures. The most striking ones are the "petrified mummies", which have preserved not only skin prints, but also hardened muscles. If you don't believe us, see here. The second find is recent, and shows an unexpected thing: hadrosaurs had a much more massive tail than traditionally thought. If this’d be true for all dinosaurs, then many classic studies about dinosaur biomechanics should be reviewed. For example, hadrosaurs and Iguanodon are often thought mainly quadrupedal, but a heavier tail would made 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.

Anatosaurus deserves the "duck-billed dinosaur" title more than any other hadrosaur, with its very flat head and spatula-like beak. Edmontosaurus sensu stricto had a stockier head and a an undulating-edged upper bill, but was still more duckish than most relatives. Their Donald Duck-like face made these dinosaurs unusually nice-looking, making consequently ridiculous their possible portrayal in fiction as dragonlike monsters — resulting more similar to giant duck-lizards. In popular work, their "duckness" may even be strongly exaggerated, rendering its flat bill literally identical to a duck's, without any teeth or cheeks. In Real Life, hadrosaurs were not exactly toothless. Behind their bill they had up to a thousand teeth closely packed together in "batteries" and capable to grind the toughest vegetation (fossil pine needles have been found in the aforementioned mummies), making them the land-vertebrates with the highest number of teeth of every time.

Maybe these hadrosaurs had a flap of inflatable skin on their nose to amplify their calls, but this is only a supposition popularized by dino-books. Traditionally Edmontosaurus and Anatosaurus have been considered the crest-less hadrosaurs par excellence, because their skull didn't show any bony prominence; but recently science marched on again and a specimen was discovered to have had a small, fleshy cockscomb on its head; this thing was discovered only thanks to the pietrified soft tissues found — maybe other "crestless" dinosaurs had some sort of fleshy protrusions on their head. After all, chicken skeleton doesn't show sign of their fleshy crest and appendages.

Here’s a brief summary of the edmontosaurines’ awesome taxonomic tangle. Their first remains, isolated teeth found in USA, were named Trachodon mirabilis ("admirable rough-tooth") in 1856 — among the very first dino-remains described in North America. During the following Bone Wars, two skeletons found by Edward Cope were discovered and named Trachodon copei. Soon later, two spectacular hadrosaur "mummies" (Claosaurus annectens) were popularly referred as the "Trachodon mummies." In 1917, a gigantic hadrosaur was discovered in Alberta near Edmonton, and named Edmontosaurus regalis ("regalis"= royal). In year 1942, one scientist found that Trachodon must be only used for the original teeth, and coined a brand new name, Anatosaurus ("Duck lizard"), for both the Bone Wars skeletons (Anatosaurus copei) and the mummies (Anatosaurus annectens). Before the year 1990 two well-known genera were thus recognized, Edmontosaurus and Anatosaurus, and described as two distinct hadrosaurs in dino-books and documentaries. However, in that year, new studies showed A. copei being much more different than A. annectens and E. regalis put together, and scientists changed Anatosaurus annectens in Edmontosaurus annectens ("swimming Edmonton's lizard"). At this point the copei was the only remained Anatosaurus, but... taxonomic rules say "Anatosaurus" should indicate only the annectens. This meant it should be renamed, too. Being scientists often very nostalgic, they decided to recall it with a similar name: Anatotitan ("giant duck"). And now Anatotitan should probably be sunk into Edmontosaurus, while Anatosaurus could return valid again.Quite simple, isn’t it?

Trachodon first appeared in pop-media in 1925 (The Lost World film adaptation), in which is portrayed as a prey for a giant carnivore. Since then, it became THE duckbill in public consciousness, to the point "trachodont" was also used as a popular synonym of "hadrosaur" (a bit like "brontosaur" as a synonym of sauropod). Since the "renaissance" times, Anatosaurus has become the most widely-used name. After 1990, Trachodon rapidly disappeared in pop-consciousness -– even though its ghost is still seen sometimes. As it seems, the name Edmontosaurus hasn’t gone a long way in non-docu media: when an edmontosaurine appears, is simply known as "duckbill," and the crested Parasaurolophus has become the most portrayed hadrosaur today. Compensating this, edmontosaurines remain still quite common in documentary media, being the only hadrosaurs which could have met Tyrannosaurus rex in Real Life (with the possible exception of the crested Hypacrosaurus, which lived from 75 to 67 million years ago). Current dino-books usually show them with the name Edmontosaurus, while "Anatotitan" became popularized by Walking with Dinosaurs, and has also appeared in its spinoff Primeval.

  1. Entry Time: 1925
  2. Trope Maker: The Lost World (film)

The Good-Mother Dinosaur: Maiasaura *

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

Hundreds of Maiasauras were discovered together in Montana in year 1980 by famous paleontologist Jack Horner (better known as the Jurassic Park 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 maiasaurs could feed the young to make them surviving until they grew larger and finally could leave their nest alone. Horner gave a Meaningful Name to his caring dinosaur: Maiasaura peeblesorum means "Peebles' good mother lizard" (note the unusual feminine suffix -saura). It was just his deep study about this dinosaur that has given to Horner his current prestige in the scientific community.

Horner and then other scientists made this possible reconstruction of Maiasaura lifestyle. Huge herds of possibly 10,000 individuals used to migrate across Western North America from the northern Canada south to Montana to winter in their island. 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 Maiasauras didn't brood their eggs like modern chickens do.) After the hatching, adults feed their helpless babies with good food, moved by their cute appearance: the babies’ skulls show large eyes and short muzzles like modern mammal cubs. After having developed their skeleton, the youngsters started to search their food on their own; finally, the whole herd undertook again their migration toward the North, to pass here the Polar summer. 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 big, stupid, unfeeling, oafs thing, and making Maiasaura just as common in popular books as Parasaurolophus & Edmontosaurus since then. Some years after 1980, the discover became known among pop-writers, too. Only... Maiasauras inconspicuous appearance was not interesting enough. Even though the "good mother dinosaur" and the whole argument are widely mentioned in the 1st Jurassic Park novel (which, by the way, had Horner as the consultant), this was totally overlooked in Steven Spielberg's following film. Other Hollywoodians resolved the problem in another way: giving Maiasaura's behaviour to other relatives. In The Land Before Time, the hadrosaurs (actually, every herbivorous dinosaur) migrate through the lands and hatch their young in crater-like nests made of earth. This was copied later by Disney's Dinosaur (this time the duckbills were substituted by Iguanodon). All OK? Obviously, not. We have no proof if other dinosaurs really behaved the same. It's like saying that if songbirds build cup-like nests, then every other bird must build cup-like nests just because is a bird. Mind this: have you ever seen an ostrich or a penguin brooding their eggs in a cup-like nest built on a branch?

In The New '10s, Maiasaura makes its first notable film appearance in the Japanese animated movie You Are Umasou 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 appeared unnamed in the educative U.S. cartoon series of the nineties The Magic Schoolbus as one of the seven dinosaurs met in the Time Travel made by the scholars and their teacher with the eponymous vehicle, in the usual role of the "caring mother" of its chicks. The other dinos here, all Late Cretaceous and North American, are Alamosaurus (a titanosaur sauropod), and egg-stealing Ornithomimus, a herd of Triceratops, some trumpeting Parasaurolophuses, pack-hunting Troodons, and an easily-scared Tyrannosaurus rex.

  1. Entry Time: 1990
  2. Trope Maker: Jurassic Park (the first book)

Big Crests: Corythosaurus & Lambeosaurus *

Hadrosaurs were very diversified in Real Life. Even though they shared the same body-plan, their head was wildly diverse. They are divided in two main lineages: basically, those with hollow crests, and those without. Other than Parasaurolophus, the only hollow-crested duckbill with a significant number of appearances in pop-media is Corythosaurus. Naturally, the latter has been a rarer sight. In theJurassic Park film series Corythosaurus joins Parasaurolophus only in the third film. Just like Parasaurolophus, good luck if you'll ever hear Corythosaurus named in fictional media. 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 the same size of Parasaurolophus (9 m long), and lived in Late Cretaceous North America 77-76 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 (68-65 mya), this makes a slight Anachronism Stew case. If the artist did the research these two hadrosaurs will interact with other smaller tyrannosaurids like Albertosaurus or Gorgosaurus. First discovered in 1912 by Barnum Brown (B. Brown is also known for having found the very first Tyrannosaurus skeletons in Montana some decades before), the "cory", unlike the "para", has one of the richest records among hadrosaurs. Several complete specimens are known to science, including many juveniles. The corythosaur’s cranial structure was similar to the parasaurolophus, with relatively narrow duckbill compared with Edmontosaurus and expanded nasal bones which formed a crest. However, the Corythosaurus crest was very different than Parasaurolophus: it was laterally-flattened, round-shaped, and put upright above the head. It shape has often been compared to a Greek helmet or to the crest of the cassowary bird (Corythosaurus just means "helmet lizard"; its full name, C. casuarius, means "cassowary-helmet lizard"), but some have more prosaically defined it as frisbee-like or dish-like. This crest was hollow like that of Parasaurolophus, but with less complex internal structure. It seems very different-sized and also different-shaped between genders and growth stages: adult males have the biggest, tallest and roundest ones, while those of females and youngsters were smaller and narrower, and the hatchlings were born devoid of it.

Issues regarding the possible functions of the corythosaur’s crest are like those regarding Parasaurolophus. Like Corythosaurus, female Parasaurolophus could have had shorter crests than males. Even though some skulls do show some variability, Parasaurolophus fossils are too rare to make a correct comparison — maybe the different-crested specimens are just different species within the genus. Since hadrosaurian crests are so differently-shaped, experts have concluded that they had also the function to distinguish visually the different hadrosaur species/genders/growth stages from each other, just like modern antelopes with their distinctive horns — let’s face it, comparisons with antelopes do work very well when talking about hadrosaurs. Moreover, the different-sized crests made differently-pitched sounds. As trombones emit lower notes than trumpets, adult males’ voices were lower than females, which in turn were lower than youngs. Then, as French horns and bassoons have a different timbre, so would have been for Corythosaurus and Parasaurolophus.

Even though is often passed off, hadrosaurs were the biggest plant-eating non-sauropodian dinosaurs. The most massive species were taller, longer and heavier than even the larger ceratopsians, stegosaurs, or ankylosaurs. And though not necessarily taller/longer, thanks to their massive bodies, they were heavier than giant theropods like Tyrannosaurus and even Spinosaurus itself! But which kind was the record-holder? Traditionally, two hadrosaurs have contended the record: North-American Lambeosaurus and Chinese Shantungosaurus. Lambeosaurus ("Lawrence Lambe's lizard"), one of the most striking-looking hadrosaurs, has also a rich fossil record, with two distinct species described plus a putative third one reclassified in 2012 in a brand new genus, Magnapaulia. Lambeosaurus has also given its name to one of the two main hadrosaurian subgroups, Lambeosaurines aka hollow-crested duckbills — the other subgroup is called Hadrosaurines or Saurolophines (see below): Parasaurolophus and Corythosaurus are, thus, lambeosaurines.

Overall, Lambeosaurus was similar to Corythosaurus with a flat, vertical crest with the same hollow spaces. However, the crest of the most known species (Lambeosaurus lambei) was taller, narrower, more rectangular, and with a secondary point raising backwards: a sort of “glove” with the “thumb” placed at 90° in respect to the main body - it is possible though, that only males did have that secondary point. The other confirmed species (Lambeosaurus magnicristatus, "big-crested Lambe's lizard") had a more rounded crest without the secondary point, but was spectacularly big and pointed slighty forwards. Magnapaulia laticaudus (former "Lambeosaurus laticaudus"), even though poorly-known with no known skulls, has the distinction to be the biggest North American hadrosaur known so far: 15m/50ft of length and perhaps 12 tons of weight, twice the weight of a Tyrannosaurus rex. While the two confirmed species were “only” 10 m long and weighing 4/5 tons, the same size as most hadrosaurs. Significantly, the normal-sized Lambeosauruses have classically been oversized in books, to match Magnapaulia.

  1. Entry Time: 1940 (Corythosaurus); 1990s (Lambeosaurus)
  2. Trope Maker: Fantasia (Corythosaurus); Dinotopia (Lambeosaurus)

USA and China make Peace: Saurolophus *

In general, Late Cretaceous dinosaurs are very similar in Western North-America and Eastern Asia. This because these landmasses were uned at the time by a stripe of dryland where today is the Bering Strait. This means that dinosaurs at the time could wander from one continent to another. Nonetheless, Asian and North American dinosaurs are usually classified as distinct genera: see Tyrannosaurus rex and Tarbosaurus bataar for example.

But there is also an exception: Saurolophus is perhaps the only dinosaur whose North American and Asian remains are always classified in the same genus, though to distinct species. First discovered in North America during the “Canadian dino-rush”, Saurolophus has left few fossils in Alberta, but much more have been then discovered near China during the Russian dinosaur-hunt in Mongolia in the 1950s (at the time Mongolia was under USSR influence) which followed the first American one led by Andrews in the 1920s. The Asian species, Saurolophus angustirostris ("narrow-beaked crested lizard"), still remains today the most abundant duckbill from Asia.

However, its North American species, Saurolophus osborni ("Osborn's crested lizard") has also been important initially. Think about Parasaurolophus: discovered soon after Saurolophus, its name just means “near Saurolophus” or "almost Saurolophus". Indeed, both dinosaurs were superficially similar, with a bony “horn” pointing backward from the rear-end of their skull. But that of Saurolophus was far shorter, more pointed, curved upwards and not downwards, and this time really horn-shaped; and was made by solid bone, not hollow like that of the parasaurolophus.

The two “horned” duckbills tend often to be confused each other by non-specialists - and their similar names don’t exactly help to resolve the mixup, too. The main example is seen in The Land Before Time: Ducky, the hadrosaurian member of the Five-Man Band of dinosaurs, has a clearly Saurolophus-like crest, and yet has been labeled Parasaurolophus. Astonishingly Saurolophus was closer to crestless hadrosaurs like Edmontosaurus than to Parasaurolophus! Indeed, Saurolophines is an alternative name for the subfamily of hadrosaurids including Edmontosaurus. Just like Edmontosaurus, Saurolophus has often been depicted in paleo-art with a speculative, inflatable, frog-like air-sac on their snout, but this is not demostrated. This air-sac was conceived as a mean to amplify sounds just like the hollow crests of Corythosaurus & Parasaurolophus.

  1. Entry Time: 1988
  2. Trope Maker: The Land Before Time (identified as "Parasaurolophus")

The decayed Nobleman: Kritosaurus & Gryposaurus *

Most hadrosaurs have been described in Alberta at the beginning of the XX century, in the second memorable “Dino-Rush” led in North-America. Among them, one of the most historically relevant has been Kritosaurus, a Hadrosaurine/Saurolophine hadrosaur. Other than the skull, hadrosaurines and lambeosaurines were distinct in other ways: the neural spines of the latter were taller, and their ornithischian backward-pointing pubis was more rounded at the tip.

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 Five Hadro Band. This “band” has also appeared once in cinema: in 1940, the “Rite of Spring” of 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, from the Navajos people.

Then, Science Marches On hit hard this duckbill. Recent studies made since the 1990s showed that its first skull with the classic bulge actually pertained to another duckbill, Gryposaurus notabilis. To worsen things, the genus Kritosaurus has revealed to be a wastebasket-taxon, and most of its former remains are now of uncertain attribution — some labeled "K. australis" in the 70s were found in an unusual location for duckbills, South-America (Argentina). Today, we even don’t know if the kritosaur had really the classic bump on its nose, and “Kritosaurus” has now become a poorly-known genus just like Hadrosaurus (below).

Gryposaurus notabilis ("noble hooked lizard"; not "noble griffin lizard" as usually said) was found in 1910, and owes its name from its hump-like nose: but its bumped skull was before the 1990s mostly attributed to the genus Kritosaurus. After that date, it was confirmed that the skull belonged to it instead. Gryposaurus has, in a sense, taken the heritage of the “decayed nobleman" Kritosaurus becoming the new “bulge-nosed hadrosaur” in popular portrayals.

  1. Entry Time: 1940
  2. Trope Maker: Fantasia

The First-known U.S. Dinosaur: Hadrosaurus *

Surprise: “hadrosaur” not only means one precise group of related dinosaurs, it also indicates a single genus of duckbill: Hadrosaurus foulkii. But its importance is almost-entirely historical.

Among stock hadrosaurians, Hadrosaurus, Kritosaurus, Gryposaurus, Edmontosaurus, Saurolophus, and Maiasaura were Hadrosaurines, the most basal (and according to sone, artificial) subfamily of duckbills, some with small bony headcrests and other without them at all. The more evolved, huge-crested lambeosaurines are a confirmed natural group, but have fewer kinds described by science; the stock ones are Corythosaurus, Lambeosaurus and Parasaurolophus.

The very first dinosaur ever identified as such in America (and outside 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”; and, oddly for an US dinosaur, was found in New Jersey – since dino-discovers in Eagle Land began in the East Coast while the upcoming “Bone-Wars” were “fought” in the West, one could say about a veritable Dino-Rush. Hadrosaurus foulkii (William Foulke was its first discoverer) was already recognized as an Iguanodon relative, but the latter was still depicted as totally-quadrupedal at the time. Hadrosaurus remains, though very incomplete, cleary showed an at least partly bipedal creature. Joseph Leidy (its namer) was the first paleontologist to have described a large-sized dinosaur in the classic upright posture: a revolutionary idea at the time, which became more popular later, expecially after the countless portraits of another guy, guess who.

Hadrosaurus has also the distinction to have been the first dinosaur ever mounted in a museum; however, the original bipedal posture has changed from upright to horizontal since the 1970s. Sadly, Hadrosaurus skull was pratically unknown, so Leidy didn’t understand to be in front of “the first duckbill discovered”. Despite this, some books have portrayed Hadrosaurus with a bump-nosed head for some reason, like what has happened to Kritosaurus. Actually, Hadrosaurus is so incomplete that it could be a synonym of another kind of hadrosaur, though a recent study seems not to agree.

Hadrosaurus was the animal originally chosen by Michael Crichton for the "stampede scene" in his Jurassic Park first novel, while Spielberg's following film chose to substitute it with the ornithomimosaur Gallimimus. Sometimes Hadrosaurus is confused with Edmontosaurus in popular non-fictional representations.

  1. Entry Time: 1990
  2. Trope Maker: The Jurassic Park novel

Other hadrosaurs

Sorry, these ones aren't here. If you're looking for Tsintaosaurus, Shantungosaurus, Hypacrosaurus, Prosaurolophus, Secernosaurus, Brachylophosaurus, Olorotitan, Charonosaurus, Telmatosaurus, Tethyshadros, Velafrons, and others, see here.

    Hadrosaur Predecessors 

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); Muttaburrasaurus is probably the most portrayed dinosaur of Australia. Lesothosaurus and Heterodontosaurus are here for convenience, but are not true ornithopods anymore according to modern knownledge.

The Veteran of the Dinosaurs: Iguanodon **

https://static.tvtropes.org/pmwiki/pub/images/iguanodon_-_copia_1718.jpeg

Living 126 to 125 million years ago in Early Cretaceous Europe, this is the most iconic non-avian dinosaur from the "old continent" together with Compsognathus, Plateosaurus, 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 expecially 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 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 portaits 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 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 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 a 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 about 40 Iguanodon skeletons were discovered within a coalmine in Belgium near the town of Bernissart, the very first "dino graveyard" ever found. 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".

Most dinosaurs have changed their look at least once: Iguanodon has done this twice. The first attempt of reconstrution showed 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 discover of the complete skeletons from the "dinosaur mine" in the 1870s, the iguanodon became 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 hiddening the teeth in the living animal. note  An excellent example of this new portrait is seen in Disney's Dinosaur, which made Iguanodon the main character in the story — 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 Dinosaur and Walking with Dinosaurs were broadcast during the 20th-21st century change. Rule of Cool easily explains why: with its generic look and weak weapons, it don’t bear the comparison with Tyrannosaurus rex jaws, Triceratops horns, Stegosaurus plates, "raptor" claws, or the immense size of 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 uncospicuous. However, its historical and scientifical importance won't ever be deleted in dino-fans' consciousness, as no other dinosaur has run the whole two centuries of popular portraits: from Crystal Palace rhinos, to giant two-legged iguanas, up to Disneyan horses.

  1. Entry Time: 1854
  2. Trope Maker: Crystal Palace Park

Tree-Climber or Ground-Runner?: Hypsilophodon *

When we think about small bipedal dinosaurs our mind authomatically 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, 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 some attributed to Hypsilophodon come from North America.

A very small dinosaur, 2 m long or less, the bulk of a large dog, Hypsilophodon foxi ("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 quickiest-running dinosaurs. If alive today, it would probably appear one of the cutest-looking dinos, maybe even suitable as a good 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 iguana, and long depicted in this way in books, 3D models, and perhaps even fiction. Few other dinosaurs have had such a great Science Marches On change during their story: maybe only Spinosaurus is rival, as it switched very recently from a land long-legged theropod to a water short-legged carnivore. While Iguanodon was often reconstruted using a classical kangaroo as a model, Hypsilophodon was often compared with the "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 Red Shirt, little more than a bite-sized snacklet for the big hungry carnivores. This portrayal can be shared with small theropods as well, expecially the toothless ones. Hypsilophodonts are often cited with ornithomimids as examples of harmless dinos: ostrich-dinosaurs too had a graceful appearence, 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 closerly-related to them). A singular case is in The Land Before Time 3rd film, in which the leading villain of the story is a strange-looking puppy of Hypsilophodon named Hyp who is the leader of a Terrible Trio of young dino-rivals of the protagonistic Five-Man Band (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.

  1. Entry Time: 1995
  2. Trope Maker: The Land Before Time 3rd film

The Antelopes of the Jurassic: Camptosaurus & Dryosaurus *

Let’s face it: it’s Rule of Cool 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 Jurassic Park 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 Planet Dinosaur, which portrays it as a simple fodder for the allosaurs?

Camptosaurus lived in Late Jurassic North America just alongside dino-stars like these: Brontosaurus, Diplodocus, Brachiosaurus, Stegosaurus, and indeed Allosaurus: it could have shown up in Walking with Dinosaurs, The Ballad of Big Al or even When Dinosaurs Roamed America. Maybe its rather generic appearance (by dinosaur standards of course) was judiced kinda incospicuous 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 large-sized ornithopods, and 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 Camptosauruses 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 Turn of the Millennium, though with very minor roles — in one case, it serves only to give a prey to Allosaurus — but it doesn't appear in The New '10s-related Planet Dinosaur.

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 once considered a big "hypsilophodont", as big as the Late Cretaceous Thescelosaurus made famous in year 2000 for being the owner of the presumed "pietrified heart" that led so much controversy about dinosaurs' warmbloodedness.

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 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 manouvreable, 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.

  1. Entry Time: 1990s
  2. Trope Maker: Jurassic Park novel (Camptosaurus); Walking with Dinosaurs (Dryosaurus)

Beware my Long Tail: Tenontosaurus *

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, and was once considered an overgrown "hypsilophodont" in older classifications - more precisely, the by far biggest member of the group. It had long frontlimbs (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 Raptor Attack). Some scientists, however, 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 Jurassic Park 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 Jurassic Fight Club as the victim of a pack of deinonychuses. Finally, Tenontosaurus is also one of the chosen dinosaurs for The '80s / The '90s expo called 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.

  1. Entry Time: 1980s
  2. Trope Maker: its role as the chosen prey for Deinonychus

Duck-billed Spinosaur and Bulbous-Nosed Iguanodont: Ouranosaurus & Muttaburrasaurus *

Here’s one of the most classically-cited dinosaurian Mix-and-Match Critter 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 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 nigeriensis (the only known species) was once considered an evolved hadrosaur-like Iguanodontid, was smaller than Iguanodon and lived souther than it, in Cretaceous Sahara, just like Spinosaurus aegyptiacus (which was found a bit more northernly, ex. 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 Social Ornithopod.

In popular works the spinosaur has often been shown as the predator of the ouranosaur, the latter being smaller and thus a potentially easy prey for it; but 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 Planet Dinosaur 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, mooses 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.

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 The '80s, expecially 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, reminescent 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 unlikely 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 Koolasuchus. It seems Australian and Antarctic fauna remained primitive across the Mesozoic, perhaps until the Great Extinction of 65 mya.

Muttaburrasaurus appeared prominently in the classic Walking with Dinosaurs documentary of 1999 (in the fifth episode) as the biggest animal of its fauna, and also in one sequel of The Land Before Time (rather incorrectly, in truth).

  1. Entry Time: 2011 (Ouranosaurus); 1995 (Muttaburrasaurus)
  2. Trope Maker: Planet Dinosaur (Ouranosaurus); The Land Before Time 3rd film (Muttaburrasaurus).

Three Kinds of Teeth: Heterodontosaurus *

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

The "hetero" lived in Early Jurassic like the armored Scelidosaurus but far souther, 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 Compsognathus. Its skeletons have not left tracks of feather-like structures around them, but since its close relative Tianyulong had surely them, it's highly probable that Heterodontosaurus also had them.

Unlike the ur-tank dinosaur Scelidosaurus, Heterodontosaurus was discovered only in The '60s. 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 competiton, a bit like in male baboons or male musk-deers (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 muntjak, 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 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 Anachronism Stew and Misplaced Wildlife are in play altogether, since Coelophysis (as traditionally-intended, without the species rhodesiensis) 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 warthogs do with big cats, but this is not demonstrable due to the lack of fossilized combats like the one between Protoceratops and Velociraptor.

  1. Entry Time: undetermined
  2. Trope Maker: Its "canine" teeth

Fore-Runners: Lesothosaurus & Fabrosaurus *

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 forerunner of all bird-hipped dinos, and thought not to belong to any great ornithischian group; 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 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 The '60s, Fabrosaurus would be the valid genus name for this dinosaur. Other possible Lesothosaurus remains have been classified in 2005 in another genus, Stormbergia.

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 birdhipped 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 hypothized that Lesothosaurus underwent long "hibernations" to survive the harsh desertical 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 the triassic species of 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 Real Life. Like Hypsilophodon, Heterodontosaurus or the prosauropod Mussaurus, Lesothosaurus can also be cited as an example of a particularly small herbivorous dinosaur.

  1. Entry Time: undetermined
  2. Trope Maker: Its former status as the precursor of the other ornithischians

Other hadrosaur predecessors

Sorry, these aren't here. If you're looking for Thescelosaurus, Altirhinus, Orodromeus, Rhabdodon, Parksosaurus, Othnielosaurus, Scutellosaurus, Pisanosaurus, Eocursor, Tianyulong, Kulindadromeus, and others, see here. And here.


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