Useful Notes / Stock Dinosaurs (Ornithischian Dinosaurs)

Ornithischian Pelvis

This page is about the stock ornithischian dinosaurs. Ornithischians ("bird-hipped dinosaurs") included a variety of usually herbivorous dinosaurs, like Ceratopsians, Stegosaurs, Ornithopods, and Ankylosaurs: some big and other small, some bipedal and other quadrupedal, and others in part bipedal in part quadrupedal. All were united by their skeletal anatomy, especially their specialized jaws and pelvis (the pelvis is in the image above). Unlike the saurischians, they were definitely a natural grouping of dinosaurs, having risen 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 and the largest known member, 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 ***

Armored Roof Lizard

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. It lived in Late Jurassic North America, 155 to 150 million years ago, and was discovered during the Bone Wars like several other dinosaur species (Allosaurus, Diplodocus, Brontosaurus etc.) ^note but not Tyrannosaurus: this one was found well after the end of the Wars.

The several Stegosaurus species ranged from 24ft/7.5m up to 30ft/9m long, and weighed from 1.5 up to 5 metric tons. The two most known have been S. stenops (stenops = "narrow face") and S. ungulatus (ungulatus = "the hoofed one"). Its plates and deep body made it look bigger than it was when seen from the side: actually, the stegosaur’s body was laterally flattened, and not as heavy as it seems. Its limbs were pillar-like; the front legs were much shorter than the hind legs, and the neck was set low above the ground (but not the degree seen in old portraits). Despite its overall size, Stegosaurus had a remarkably small head, with room for only 2.8 oz/80 g of brain: often stated as "walnut-sized", but actually it was larger than a walnut, closer to an apple in size. This has made it the most iconic dinosaur within the 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 purposes.

The plates are the distinctive stegosaurian feature, and every stegosaur portrait shows them: without them, stegosaurs would be easily mistaken for kinda sauropod things. 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 impressions suggests the former is more likely. Defense, thermoregulation, and display (mating or threat) are the classic hypotheses, but we have no definitive proof for any of these ideas. 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 too irregularly placed to be used as armor, leaving the animal's sides unprotected — although if covered in horn, they might have had sharp edges, which would make them more effective as defense. The "solar panel/radiator" theory has been one of the most popular since the Dino-Renaissance: it could explain why they were apparently 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) and turtle shells show they have usage for thermoregulatory 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. Although Stegosaurus has left dozens of specimens, they are usually found with misplaced plates, making them sort of a 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. Interestingly, all of Stegosaurus' relatives displayed paired lines of plates, making the "stego" unusual for its kind.

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 hypothesized 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 thagomizers, 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 would have 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 S. ungulatus made soon after its first scientific description, in late 1800. Or it can have no tail spikes 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 sideward-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), gave it further protection. No eggs and nests are known, but there are many specimens of 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, full-name Kentrosaurus aethiopicus.

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 zigzagging), 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". Studies of its hips also tell us it had an insanely good turning radius, suggesting it would have protected itself from predators by constantly turning its shoulder and back spikes towards them and its head away from their claws and teeth.

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, Dicraeosaurus, and Tornieria (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. Some scientists have raised concerns about this, leading to efforts to rename Kentrosaurus by such names as "Kentrurosaurus" ("pointed-tailed lizard") and "Doryphorosaurus" ("lance-bearing lizard), but the rules of scientific naming mean none have stuck.

1. Entry Time: 1988
2. Trope Maker: Dino-Riders

The Unpronounceable: Tuojiangosaurus *

Together with Kentrosaurus, the most portrayed non-Stegosaurus stegosaur in popular dino-books has been Tuojiangosaurus ("Tuo River lizard") — don't worry if you cannot pronounce that "jiang" correctly, unless you are Chinese or Chinese-speaking of course. Its whole scientific name is Tuojiangosaurus multispinus, "many-spiked Tuo River lizard". Other two classic Late Jurassic dinosaurs from the same country have also geographically-referenced names, Mamenchisaurus (after Maming Brook) and the allosaur-relative Yangchuanosaurus, after the Yongchuan district in the city of Chongqing.

Discovered in 1977 and described by Chinese paleontologist Dong Zhiming, Tuojiangosaurus was overall more similar to Stegosaurus than to Kentrosaurus (some quote it as the stegosaur's "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 intermediate between Kentrosaurus and Stegosaurus. Tuojiangosaurus had narrow, paired plates like the former, but a four (thagomizers) 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 uncertain whether it really 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 Game as one of the dinosaurs cloned in the park.

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

Other stegosaurians

Sorry, these ones aren't here. If you're looking for Dacentrurus, Huayangosaurus, Wuerhosaurus, Chialingosaurus, Chungkingosaurus, Lexovisaurus, Loricatosaurus, 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, a 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, armor plates that formed a keratin-covered shell with short spikes in many directions, and a tail club in all but 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 the nodosaurids: the polacanthines (including Polacanthus and until recently, Gastonia, and possibly Hylaeosaurus), variably classified as either closer to ankylosaurids or to nodosaurids. The short-named Minmi of Australia and the "south-polar" Antarctopelta have been hard to classify, but seem to form a unique lineage southern continents-only ankylosaurians called the Parankylosaurians. Finally, the early Jurassic Scelidosaurus is usually considered basal between stegosaurs and ankylosaurs, but since the 2000s, has often been considered an extremely primitive ankylosaur well outside the three subgroups above.

The Living Tank: Ankylosaurus **

Popularly as a "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, but usually estimated to be about 20-26 ft (6-8 m). It has traditionally been 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 relatives being 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 has been famous since the 1940s as the most extreme example of an armored dinosaur (although some of its relatives were likely even more heavily armored). 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 ankylosaurs frequently (hadrosaurs were much more abundant and armor-less). Despite their heavy build and short legs, ankylosaurs 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 T. rex a fatal blow with its tail mace. When the tyrannosaur is shown winning the battle, it's seen "overturning" the ankylosaur to expose 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 rarer 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. It seems that baby ankylosaurians gathered in groups, as their armor wasn't fully developed yet.

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 justifies 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 Dinosaur: 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 they were much smaller-sized, stegosaurians and ankylosaurians tend to be shown as slow-moving as the sauropods: ex. the aforementioned Url 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 *

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 Just like Centrosaurus and so on which were smaller than their "younger" relative Triceratops. 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 cutleri, 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, films, and toylines 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 "Euoplo" and "Scolo" only had Gorgosaurus and Daspletosaurus to battle doesn’t help. Some dino-books wrongly portray Scolosaurus/Euoplocephalus living and fighting against Tyrannosaurus rex, which actually lived later.

1. Entry Time: 1940s
2. Trope Maker: Zdenek Burian's painting (actually Scolosaurus)

Club or Spikes?: Scolosaurus *

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

Scolosaurus is known from one really well-preserved skeleton from Alberta and several more incomplete specimens from Montana (the latter of which are sometimes given their own genus, Oohkotokia). It was about the same size as Euoplocephalus, lived 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 as "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 discovery of the first ankylosaurian in England, a companion was added: Polacanthus foxii. English too (some dubious remains from the USA were once also attributed to its genus), and conviving with Iguanodon and Hypsilophodon in the Early Cretaceous, Polacanthus was rather small compared to Ankylosaurus or Euoplocephalus being 4m/16ft long, and the first remains found in the Isle of Wight were very incomplete. This explains why in older depictions Polacanthus had very light armor, consisting only of pairs of long dorsal spikes (hence the name, "many spines"), a bony shield on its hips, and pairs of small triangular plates on the tail. This kind of armor is typical for the polacanthines, the subgroup of ankies which it's the archetype of. But some portrayals took it a further step, and gave it a stegosaur-like thagomizer, or a small ankylosaurid club. The spiked-tailed polacanth made cameo appearances in 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, homonymous 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 appearance has also involved the official archetype 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 since treated as a dubious wastebasket taxon for undetermined ankylosaur remains. The clubbed Ankylosaurus and Euoplocephalus were both found later than Polacanthus and Nodosaurus, in the early 1900s in Alberta, Canada.

Nodosaurus ("tubercled lizard") was bigger than the Polacanthus, but smaller than Ankylosaurus proper — about the size of the Euoplocephalus. Curiously, like what happens sometimes to Ankylosaurus, in classic portrayals, Nodosaurus is shown with simple armor lacking any spikes. Why? Because the specimen found by Othniel Marsh was devoid of them; in reality, it likely had long spikes protruding from both sides of the body as all other Nodosaurids did. Obviously, we don't know how long these spikes were, since they've never been found.

A strange-looking Nodosaurus appears in the second sequel of The Land Before Time 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 or near-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 III: The Time of the Great Giving (Nodosaurus)

The Asian Clubtail: Pinacosaurus *

Many ankylosaurs are known from Asia. Pinacosaurus grangeri ("Granger's plank lizard"), the most common in the fossil record, was basically the equivalent of Euoplocephalus and 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. Other Asian ankylosaurs, the bigger but younger and less common Tarchia and Saichania were more similar to Ankylosaurus; the older, mid-sized Talarurus was unusual, being barrel-shaped and short-limbed.

First found in 1920s, Pinacosaurus was the first armored dinosaur found in Asia, by the same expedition led by Roy C. Andrews that first found Velociraptor, Protoceratops, Oviraptor, and the latter's eggs. Pinacosaur remains found later in the 1950s were wrongly labeled "Syrmosaurus". In 1988, Pinacosaurus contributed to the Dinosaur Renaissance by giving 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. Instead, it seems that young ankylosaurians were gregarious animals, since their armor was much less developed than the adults.

Pinacosaurus has appeared in speculative documentaries or mockumentaries and books 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 programmers chose a juvenile pinacosaur for the "raptor"'s meal. In the show, the dromaeosaur kills Pinacosaurus by cutting its throat with its sickle-claw after a hard battle.

1. Entry Time: undetermined
2. Trope Maker: documentary media

The First Known Ankylosaur: Hylaeosaurus *

Huge Ankylosaurus has not always been THE ankylosaur. It was discovered at the beginning of the 20th century, but several relatives were already known. They were simply smaller, less armored, and above all, very fragmentary, and in the 19th century, were classified among the Stegosaurs. As a group, the Ankylosauria were recognized as distinct only after Ankylosaurus was found. With all that in mind, it's interesting that one of the three inspirers of the name “dinosaur” was just an ankylosaur: Hylaeosaurus armatus ("armored 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. Among the famous Crystal Palace Park statues in London made in 1852 by Benjamin W. Hawkings, the Hylaeosaur shows up with the Megalosaur and Iguanodont, and is depicted as larger than it was in Real Life. Unlike the other two "original stock dinosaurs", it has remained totally 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 simpler version of the Crystal Palace Iguanodon and Megalosaurus.

Hylaeosaurus usually gets mentioned together with its two companions when the Crystal Palace Dinosaurs sculptures are portrayed in media. In the John Sibbick-illustrated Great Dinosaur Encyclopedia published in year 1985, Hylaeosaurus is shown more correctly with a complex armor with sideward-pointing spikes: once considered a nodosaurid because of its lack of club, it is today thought by some to be closely related to 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 especially for ankylosaurians, but also for many other dinosaur subgroups — sauropods like Jobaria, theropods like Nedcolbertia, stegosaurians like Miragaia, basal ornithischians like Leaellynasaura, 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 burgei was a middle-sized 4.5 m long ankylosaur from the Early Cretaceous, smaller than the 7 m long Late Cretaceous Edmontonia longiceps and the even larger (7.5 m) but slightly later in the Early Cretaceous Sauropelta edwardsorum. 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 to the European Polacanthus, and shared with it the same spiky body and tail and the hip scutes. The Edmontonia and Sauropelta were more closely related to Nodosaurus, with long shoulder spines, no scutes above the hip, and tails lacking the long spikes of Gastonia and Polacanthus.

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 tyrannosaurids 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 used against big allosauroids like Acrocanthosaurus (tyrannosaurids still didn't exist at Sauropelta's times).

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

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

Ankylosaurs of the Southern World: Minmi & Antarctopelta *

Non-stock ankylosaurs and stegosaurs tend often to be ignored in visual media. Maybe their reputation of “slow and foolish” has done its part, even though this fame is undeserved. A good example of missed opportunity was a small ankylosaur discovered in Australia in 1980, with one of the least dinosaurian names one could imagine: Minmi, aka "the shortest-named dinosaur" until the 2000s, when it was beaten by the small theropod Mei and then the bat-winged theropod Yi in 2015. There is a backstory however: Minmi comes from “Minmi Crossing”, the locality where its only skeleton was discovered. After a second presumed skeleton was found in the early nineties (reclassified as Kunbarrasaurus in The New '10s), Minmi and this longer-named relative have since then become together the most complete Australian dinosaurs. And yet ankylosaurs do not appear in the Walking with Dinosaurs episode "Spirits of the Ice Forest" set in Early Cretaceous, in which Muttaburrasaurus, Leaellynasaura, and the (now considered dubious) “polar allosaur” appear, despite being all contemporaries.

Once considered a nodosaurid, today Minmi paravertebra is a bit of a taxonomic mystery. At only 10 ft long, it is one of the smallest known, even smaller than the basal Scelidosaurus but bigger than the dwarf island-dweller Struthiosaurus of Late Cretaceous Europe. Minmi was devoid not only of tail-club but even of prominent spikes on its body, making it a bit like the primitive Scelidosaurus indeed. However, its torso was fully covered with small osteoderms of various shapes, its tail had plates, and could even have had some small bony scutes in its belly, a rare thing among ankylosaurs. Its main peculiarity, however, was some unusual internal bones along its backbone called paravertebras (lit. "beside vertebra"), which according to some allowed the Minmi to run faster than other ankylosaurs — hence its full name M. paravertebra.

The Australian Minmi was the first ankylosaur ever found in the southern hemisphere, in 1980, but it was steadily joined by a second animal in 1986: another primitive ankylosaur, this time discovered in Antarctica, and maybe related to Minmi. It was the very first dinosaur ever discovered on the Ice Continent, and yet it had to wait twenty years to be named, in year 2006, as Antarctopelta appropriately (the first dinosaur named from Antarctica was the Early Jurassic theropod Cryolophosaurus, during the 90s). Since it's known from scant remains, there's not much we can say about it. It's worth remembering however that during dinosaur times, Antarctica was not in the South Polar region, but attached to Australia in the Southern Hemisphere and totally devoid of the immense ice cap. Thus, the Antarctopelta lived in a non-glacial world like the other Mesozoic dinosaurs, although it would have experienced snow during the winter.

Like Minmi and Kunbarrasaurus, Antarctopelta proved difficult to classify for quite a while. Then in 2021, with the discovery of the South American Stegouros, it was determined that Antarctopelta, together with Stegouros and Kunbarrasaurus (and possibly Minmi, which Kunbarrasaurus was originally identified as a species of, keep in mind) formed a previously unknown branch of southern hemisphere-only ankylosaurians called the parankylosaurians, which maintained a mixture of primitive and evolved traits not seen in their northern cousins (an example of "mosaic evolution"). Antarctopelta appears in Prehistoric Planet, looking for a cave in which to hibernate through the cold polar winter.

1. Entry Time: 1980s
2. Trope Maker: Their status as the first-known "southern ankylosaurs". Antarctopelta first appeared in Prehistoric Planet.

The Earliest Tank: Scelidosaurus *

When we think about armor-bodied dinosaurs, our minds automatically come to Stegosaurus. But let’s not forget Scelidosaurus harrisonii, a very primitive thyreophoran from Early Jurassic, found in Europe and possibly Asia and North America. If the last is true, it could have met the famous double-crested carnivore Dilophosaurus in life.

4 m long, half the length of an average Stegosaurus and small for ankylosaurian standards, the scelidosaur is traditionally considered in the middle between stegosaurs and ankylosaurs, but some have suggested that it's the first true ankylosaur. Still, Scelidosaurus was slenderer, 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 ankylosaurs sensu stricto, 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, which were 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 has been known since the 19th century even before Stegosaurus and Ankylosaurus were known to science, but it was described later than the Mantell's Hylaeosaurus, by Richard Owen. Like most of the other earliest dino-discoveries, it was found in Europe (in Southern England), and reconstructing its body correctly was a long, hard task. Having a not-so-impressive appearance, Scelidosaurus has remained a rare-stock animal. However, basal dinosaurs from the Triassic and Early Jurassic often make paleontologists happier than their Late Jurassic or Cretaceous counterparts, 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, Sarcolestes, Struthiosaurus, Gargoyleosaurus, Talarurus, Tarchia, Tianchisaurus, and others, see here.

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Armor-headed Plant-Eaters

The most recent group of ornithischian dinosaurs, the marginocephalians have been usually discovered in Late Cretaceous rocks. They were closer to the ornithopods (see further) than to the thyreophorans (see previous), and are divided in two very different subgroups: the ceratopsians and the pachycephalosaurs, both unified by their armored heads. The former can be further divided into 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 their 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: the chasmosaurines (those with long frontal horns, a short nasal horn, and (usually) long frills); and the centrosaurines (those with a short frill, no frontal horns, and (usually) a long nasal horn). Triceratops, Torosaurus, Chasmosaurus, Pentaceratops, and Anchiceratops are member of the first subgroup, while Styracosaurus, Centrosaurus/"Monoclonius", and Pachyrhinosaurus belong to the second one. Leptoceratops and Microceratus/Graciliceratops belong to neither, but were both similar and related to the two guys below.

Protoceratops and Psittacosaurus have been the prototypical ancestral ceratopsians. They were much smaller than the proper ceratopsids, roughly as big as a sheep or a pig — in vivid contrast with their rhino-sized or elephant-sized cousins.

T. Rex's Rival: Triceratops ***

Horrible Three-Horned Face

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

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" (synonymized with T. horridus. T. horridus is likely the ancestor of T. prorsus, as the former lived slightly earlier than the latter; this is supported by the existence of several trike specimens that appear to be transitional forms with traits from both species. Another Triceratops species T. hatcheri, known only from one skull, has been suggested by some to represent a different dinosaur called Nedoceratops (formerly Diceratops until it turned out a wasp already had that name), but other scientists think it represents a diseased specimen of T. horridus.

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 due to people imagining it as "the only plant-eater able to defeat the Big Bad Tyrannosaurus rex" — even though ankylosaurs and maybe the biggest hadrosaurs might also have been able to defeat T. rex 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 that began in 1988. In older films, the trike tend often to be portrayed more like a Prehistoric Monster, like in Ray Harryhausen's One Million Years B.C..

Compared to other stock dinosaurs, Triceratops and its relatives have been portrayed fairly accurately, and our understanding of their appearance has changed very little over the years. 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 thought 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 have described horned dinosaurs as prehistoric boars, rather than the more classic comparisons with rhinos and buffalos, with some even going as to far as to suggest they were omnivorous^note Like all herbivores do today, they probably would have supplemented their vegetarian diet with a bit of protein every now and then, but they weren't specially adapted to eat other animals.

Triceratops and T. rex have been shown fighting in modern works from the first dino movies and through the whole paleo-artistic tradition (including one especially iconic painting by Charles R. Knight). In these battles, the percentages of victories between the rex and trike appears to about 50%. Though all this may be Truth in Television, it's likely that T. rex preferred younger and more vulnerable prey than an adult Triceratops. Since it's often considered the badass 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 at everything, and may even moo like bovines. Another classic trope 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 on their offspring, just like musk-oxen actually do against wolves when attacked, or even like what American pioneers did with their wagons against their enemies: this is a possibility, though not proven, conceived during the Dinosaur Renaissance.

The ceratopsids' horn structure was more like cattle's than rhinos': that is, bony protrusions covered with a horny sheath. Their function is still debated: some think the frequently-seen scenes of Triceratops goring a big carnivore to death or locking their horns like deer in head-vs-head combat might not reflect reality, and that the frontal horns were too fragile and not pointed enough to be used as weapons, instead simply being display devices. However, injuries on Triceratops specimens match their horns pretty well, as do the presence of bite marks from T. rex on trike horns (including one that was bitten in half and showed signs of healing). Additionally, given that the keratinous sheath would have made the horn less likely to break and helped better shape it, goring would still be plausible. However, the most likely answer was "all of the above"; Triceratops would have mostly used its horns to fight and show off to each other, but when cornered by a hungry T. rex, they would be deadly weapons in a pinch. Interestingly, individual variation is common in Triceratops; some specimens show curved frontal horns, while others had straight horns. The frill was variable too: some individuals had tubercles on the 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 they were arguably adapted to eat fibrous plants, not to tear meat — or at least this was not the main function. Some think 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 further, or they may have been only for display.

There is one thing that most paleomedia gets wrong, though - portraying Triceratops as living in large herds. Unlike many of its relatives, Triceratops fossils have never been found in bonebeds containing dozens of individuals, indicating they were either solitary or lived in small groups. The latter theory would ultimately be confirmed in 2024, when five individuals were found at one site.

1. Entry Time: 1918
2. Trope Maker: The Ghost Of Slumber Mountain (film)

Crowned Head: Styracosaurus **

Alberta's Spiked Lizard

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

Styracosaurus frill spikes were not true horns as commonly said, but only an exaggerated version of those protuberances commonly seen in ceratopsid species. Even though the most common portrayal has six spikes, it seems most specimens had only four. But don’t rule out seeing styracosaurs with eight spikes (like in Disney's Dinosaur) or more in popular works, or even with no frill and the spikes protruding directly from the back of the neck like the horned lizard of the deserts of North America.

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, the ceratopsian 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 and were brightly colored in either male or female individuals when alive. Ultimately though, it's completely impossible that like with Stegosaurus' plates, all of these theories were at least partly true.

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

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

The Biggest Skull?: Torosaurus *

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 (such as Dino-Riders & various paleoart) because of its huge skull, long believed the biggest of any land animal that ever existed — 8-9 ft long, taller than an adult person if stood 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 look bigger than it actually was if seen from the front. According to some, the choice to give the main role to Torosaurus instead of Triceratops was just because of its bigger frill.

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

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

1. Entry Time: 1988
2. Trope Maker: Dino-Riders

Five Horns?: Pentaceratops & Titanoceratops *

Despite many of the most well-known ceratopsian genera having 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 abound here: after Triceratops ("three horned face") and Protoceratops ("first horned face", because it was a ceratopsid predecessor), the most well-known is Pentaceratops ("five horned face"). But did it really have 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 large in Pentaceratops. One of the classic chasmosaurine ceratopsids, Pentaceratops sternbergii looked practically like an intermediate form between Torosaurus and Chasmosaurus: smaller than Torosaurus but bigger than Chasmosaurus, lived before the former but around the same time as the latter. Its horns were shorter than Torosaurus but more developed than Chasmosaurus. Its frill was neither elliptical/smooth like the torosaur's, nor triangular/complex like the chasmosaur's: it was rectangular, and lightly serrated around its whole perimeter like that of many Triceratopses. The frill openings of Pentaceratops were very wide, like those of chasmosaurs, compared to the smaller ones of Torosaurus.

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

1. Entry Time: 2018
2. Trope Maker: Jurassic World: Evolution

Immense Herds: Centrosaurus & "Monoclonius" *

If you think Triceratops was the ultimate rhino-dino, it's 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 was maybe 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, reinforcing even more the rhino resemblance. About the frill, it was rather short and undulating-edged, with that pair of bony openings covered with skin in the living animal, present in most ceratopsians outside Triceratops and a few others. But the most unexpected thing is a pair of bony “hooks” curving downwards from the top of the shield; for some inexplicable 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 20th century, most of its remains were then attributed to another relative, "Monoclonius crassus", 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 that had died together, probably killed while trying to cross a river in a flood. This discovery was one of the first pieces of concrete evidence for migrating behaviour in dinosaurs, a bit like modern caribou and wildebeest, which also sometimes die en masse 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 to 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 confusion, one can pronounce them differently: "sEn-trO-SAURus" the ceratopsian, and "kEn-trO-SAURus" the stegosaur.

About “Monoclonius” (which doesn't mean "one horn" as sometimes said, but "one sprout"), this one was a very early discovery, made in the 19th century during the Bone Wars, but is now regarded by many as far too dubious to be distinguished from the juveniles of other, better-known centrosaurines. Unlike a lot 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: Chasmosaurus *

Math is not always an exclusively-nerd thing. It can also be amusing, especially when you can apply it to dinosaurs. Chasmosaurus ("chasma" = opening, ravine, fenditure in Greek) can be recognized by the geometry of its frill: strikingly angular in shape, if seen frontally almost like 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 points 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 rest of the chasmosaur's head was less spectacular than those of the torosaur and trike: 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. It wasn't an especially big animal either, only about 4 meters long and just over a ton.

Known since the 1910s, Chasmosaurus belli is one of the most common ceratopsids in the fossil record, and is often considered the archetype of the chasmosaurines in the same way Centrosaurus is for the centrosaurines. In Fictionland, the chasmosaur was portrayed in a bunch of old movies, and some modern-cartoon "Triceratops" have a suspiciously Chasmosaurus-like triangular frill. Another noteworthy appearance is the doc Planet Dinosaur, which also shows a huge herd of Centrosaurus dying in a flood.

1. Entry Time: 1970
2. Trope Maker: When Dinosaurs Ruled the Earth

The Ceratops Family: Anchiceratops & Arrhinoceratops *

As a whole, Centrosaurs - Styracosaurs - Pachyrhinosaurs - Chasmosaurs might be considered the “predecessors” of Triceratops. The latter was elephant-sized, lived 68-66 million years ago just before the mass extinction and shared its world with the mythical Tyrannosaurus rex; the former were rhino-sized or only a bit larger, lived approximately 77-70 million years ago, and only had to worry about its “humbler” relatives (Albertosaurus, Gorgosaurus, Daspletosaurus). If you see a battle between a tyrannosaurid and a ceratopsid in some CGI documentary, expect to see more frequently Triceratops instead of the less gigantic CentroStyracoPachyrhinoChasmosaurs and other less-known species, like Anchiceratops. This one was rather Chasmosaurus-like with a similar angular frill that was instead entirely smooth laterally and entirely tubercled at its top, as well as having longer brow horns and smaller frill holes.

A relative and contemporary, Arrhinoceratops, had a similar ornamentation but a shorter frill. Both were less ancient than Chasmo/Styraco/Centrosaurus but older than Triceratops and Torosaurus. Anchiceratops ("almost Ceratops") is abundant in the fossil record, while Arrhinoceratops is a rarer find; when discovered was initially thought to lack the nasal horn, hence its prefix “arrhino-”, which means “no horns on the nose”. Anchiceratops shouldn't be confused with Anchisaurus ("almost lizard"), an ancestral sauropod-relative famous for being the first-found North-American dinosaur — and according to some, the real inspirer of the character of Dino, the Flintstones' pet dinosaur.

1. Entry Time: undetermined
2. Trope Maker: documentary media

Thick Nose: Pachyrhinosaurus *

Ceratopsids are classically known as “horned dinosaurs”: but this one seems not to have liked our definition. Pachyrhinosaurus canadensis (“thick-nosed lizard of Canada”) and the other species of the same genus (P. perotorum and P. lakustai), at a first glance, resemble more an oversized Protoceratops than a Triceratops: no true horns on the skull, a thickened boss upon the nose, often described as similar to a lunar crater, and smaller bosses over the eyes. To compensate, the 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, analogous 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 this animal is a true ceratopsid, more precisely a centrosaurine. Pachyrhinosaurus was both the largest and the last of the centrosaurines, going extinct 68 million years ago, at the same time its distant relative Triceratops first appeared. However, it's unlikely the two could have met, because Pachyrhinosaurus lived much farther north—far north enough to experience snow in the winter, in fact! The biggest species of pachyrhino (P. canadensis) was larger than the other species of its ceratopsid subfamily, but didn't reach the size of a Triceratops or a Torosaurus.

Pachyrhinosaurus was formerly one of the rarest ceratopsids in fossils: then, in the 1990s, a whole herd was discovered in Alaska in the Arctic Circle. The presence of other Pachyrhinosaurus remains much further south in Canada led scientists to suggest it as proof of migrating behavior among horned dinosaurs, but later studies determined these represented different species (P. perotorum being the Alaskan one and the other two being Canadian). 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 a sudden increase in Pachyrhinosaurus appearances in pop culture, starting as a background character in Disney's Dinosaur, then as a major character in The Land Before Time 8, and then as the lead role in the Walking with Dinosaurs film. It was, at one time, planned to appear in Jurassic World: Fallen Kingdom, but was replaced with the much more obscure Sinoceratops. Prehistoric Planet prominently features a herd of bristly Pachyrhinosaurus being menaced by a trio of Nanuqsaurus in the midst of a huge blizzard, leading to a circle-up scene similiar to what is described above under the Triceratops heading. It seems its oddness among the "classic" ceratopsids has contributed to this formerly unexpected success. Some part of its prominence can also be contributed to specimens being found in Arctic fossil deposits, leading some to imagine it as the dinosaur equivalent of the woolly mammoth or woolly rhino, complete with a speculative coat of insulating down.

1. Entry Time: 2000
2. Trope Maker: Dinosaur

Small Bipedal Trikes: Leptoceratops & Microceratus / Graciliceratops*

Try to tell everyone if the "sheep of the Cretaceous", Protoceratops, was really sheep-like. If you manage to do it, then try with this: Leptoceratops, the same length of Protoceratops but partially bipedal.

Leptoceratops gracilis ("gracile slender horned face") has probably been the most common basal ceratopsian in docu-media after Protoceratops & Psittacosaurus; like the former it too was claimed to have been a sort of "proto-sheep", this time not for being very common in fossil record but because it was literally confronted with a sheep by one scientist in The '80s. Leptoceratops was the very first small-sized ceratopsian discovered: 1910s, a decade before Protoceratops and Psittacosaurus, and has often be considered as an intermediate form between the two.

Compared with Protoceratops, Leptoceratops was not only hornless, but also lacked the "bump" on the nose seen in the former, was notably slimmer-bodied, had longer legs, and possessed a much smaller frill and huge cheek-spikes. There is a surprising thing at this point: contrary to what one might expect, Leptoceratops lived later than Protoceratops, at the very end of the Cretaceous; and roamed North America, not Asia, where ceratopsians started their evolution, thus sharing the lands with Triceratops and Torosaurus. But for some reason, it preserved the archaic bodyplan of its primitive ancestors. Like Protoceratops and Psittacosaurus, Leptoceratops could appear a quite harmless creature in a world populated by gigantic dinosaurs: however, it had extremely powerful and massive beaked jaws able to deliver strong bites, and there's also the possibility it had pointy quills on its tail like Psittacosaurus.

Despite their partial bipedality, Psittacosaurus and Leptoceratops were still robust guys compared with the “gazelle dinosaur” Hypsilophodon or the tusked Heterodontosaurus. But they also had some slimmer relatives that if it wasn't for their head, would surely be mistaken for ornithopods. The most historically relevant was aptly called “Microceratops” ("small horned face"). From Ancient Mongolia like the prototypical Protoceratops (but some 15-20 million years older), it was discovered in the 1950s by a Polish expedition, and was also originally put in the Protoceratopsid family like Leptoceratops. "Microceratops" was long believed the smallest of all the ceratopsians; now the record is disputed by other relatives. It remains one of the smallest dinosaurs ever, only the size of a rooster. It was arguably a quicker-moving animal than most other ceratopsians, thanks to its size and agile legs. Its head was unmistakably (proto)ceratopsian, with any hint of "horns" or "bumps".

Very poorly known scientifically-speaking, “Microceratops” has an unfortunate taxonomic history. Most specimens of this dinosaur were reassigned in 2000 to their own genus Graciliceratops, putting the remaining fossils to dubious to be distinguished from any other primitive ceratopsian. And of top of that, it turned out the name "Microceratops" was already preoccupied by a modern insect (a parasitic wasp), leading the scant material left behind to be renamed Microceratus ("the small horned-one"). Still, it has appeared in some popular works made before the Graciliceratops-Microceratus mess, namely the first Jurassic Park novel (here it's the smallest cloned dinosaur, but inaccurately portrayed as a tree-climber), and Disney's Dinosaur — this time as the smallest species of the migrating dinosaur herd. It also appeared under the name Microceratus in Jurassic World Dominion.

1. Entry Time: undetermined for Leptoceratops; 1990s for Microceratus / Graciliceratops
2. Trope Maker: their oddness as "small bipedal trike relatives"

The First-found Dinosaur Eggs?: Protoceratops **

Andrew's First Horned Face

Protoceratops lived 75—71 million years ago in Late Cretaceous Asia, unlike the giant ceratopsids, which were almost exclusively North American in distribution (the Chinese Sinoceratops being the sole exception). It was around 6ft/1.8m 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, who discovered its remains); a second species exists in P. hellenikorhinus (the second word means "Greek nose"). At first glance, Protoceratops resembled a miniaturized ceratopsid like Triceratops: four-legged, with the same robust body, short tail, and unmistakably 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 like they were 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 sexes might have been 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 — 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 its contemporary 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 under the assumption that since the eggs and Protoceratopses were so common they must be connected. These were the very first non-avian dinosaurian eggs ever identified. The original crushed Oviraptor specimen 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 porous like those of modern birds to permit the embryos inside to breathe: Protoceratops laid them in a circular manner, and evidence suggests they were cared for by the parents.

One especially spectacular find from 1971 consists of a Protoceratops and a Velociraptor locked in combat: they were probably buried by a sudden sandstorm or a collapsing sand dune while fighting. 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, presumably attempting to slash it open. 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. In Africa today, buffaloes have been known to suddenly attack lions minding their own business in an effort to eliminate potential threats to their herd, so its possible the Protoceratops was doing the same thing to the Velociraptor. Many Protoceratops fossils also have bite marks matching Velociraptor on them, suggesting the former was a regular prey item for the latter.

Despite its scientific relevance, Protoceratops is less portrayed in pop-media than Triceratops and Styracosaurus, likely because of its relatively modest appearance. 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 the human protagonists of the first book is a cute Protoceratops named Bix. This dinosaur appears also in many books and documentaries, usually either as a prey of Velociraptor (Dinosaur Planet for instance depicts the raptor and proto who end up becoming the abovementioned "Fighting Dinosaurs" fossil) or as the chosen victim of an egg-robbing Oviraptor. Protoceratops has also gained some notoriety as the possible inspiration for the legend of the griffin after folklorist Adrienne Mayor proposed in her book The First Fossil Hunters that the ancient Scythians saw Protoceratops fossils during their gold-mining expeditions in Central Asia and attributed them to a half-lion, half-bird beast (four legs, beak, and the frill may have been mistaken for ears or wings). However, this has been called into question, as griffins have been depicted in the art of non-Asian, pre-Scythian cultures.

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 rarely getting any consideration by writers or filmmakers — especially if they are plant-eaters. One rare exception of a fictional psittacosaur is in Disney's Fantasia.

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 125-100 mya, in the Early Cretaceous; even older and more basal ceratopsians have since been discovered in Late Jurassic China) and the forerunner of almost every other member of the group.

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 like an ornithopod than a ceratopsian externally. Once thought to be capable of walking on all fours, detailed study of its four-fingered forelimbs shows it was entirely bipedal. The main trait revealing its relationship with Triceratops and kin is the parrot-like upper bill made by a unique bone called "rostral bone", the anatomical hallmark of all ceratopsians. The hook-bill gives it the name “Psittacosaurus”: “psittacus” is Greek for parrot. Another thing that ties Psittacosaurus with its horned descendants are the prominent bony “cheeks”, far less developed than those of a Protoceratops but absent in all ornithopods. The shape of the psittacosaur's 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 very close. Its body was robust, its tail short and its forelimbs long, much more like Leptoceratops than a small ornithopod like Hypsilophodon.

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

In the 2000s, many new discoveries have further raised the psittaco's importance, making it perhaps the most scientifically well-known member of 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 purposes (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 discovery at the same site debunked the classic “Mesozoic mammals were underdogs ruled by dinos”: the cat-sized carnivorous mammal Repenomamus was 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 counter-shaded dark brown on top and a lighter brown on the bottom, like a deer or an antelope. This resulted in modellers 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 Albertaceratops, Archaeoceratops, Auroraceratops, Avaceratops, Bagaceratops, Chaoyangsaurus, Einiosaurus, Kosmoceratops, 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 most likely used for headbutting and display. Due to their unusual teeth, there is the possibility that were partly omnivorous. 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 simply be juveniles of Pachycephalosaurus; see below for more).

Thick Spiky Head: Pachycephalosaurus, "Stygimoloch" & "Dracorex" **

Wyoming's Thick-Headed Lizard

Pachycephalosaurus lived during the Late Cretaceous 68-66 million years ago in North America alongside many well-known dinosaurs, like T. rex and Triceratops. 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 — scientists once 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 it's still small compared to most stock ornithischian dinosaurs. Its actual length is uncertain: popular books often set its size at up to 30ft/9m, but a length of 15-18ft/4.6-5.5m is more likely. All of its relatives were no longer than 10 ft. Described in 1931 from a single skull, it was initially identified as Troodon because the Troodon was at the time known only from one tooth, which is similar to some pachycephalosaur teeth, and was renamed Pachycephalosaurus only in 1943. No other parts of the body have been found since then: reconstructions are typically based on smaller pachycephalosaurians, especially Stegoceras, the most complete pachy to date.

Pachycephalosaurus wyomingensis, the only known species (possibly; see below), owes its name to Wyoming. This dinosaur is distinguished by its dome-like head, which makes it look very intelligent. However, the height of the dome was almost entirely made of almost one-foot-thick bone, and its brain wasn't larger than other dinosaurs', making its nickname "The Boneheaded Dino" quite accurate. A number of bony knobs and blunt spikes around the base of the dome and on its nose contrast with the smoothness of the dome to create a look of partial baldness or a monk's tonsure, i.e. a "Roman tonsure"; hence the epithet "Friar Tuck-osaurus" in The Lost World: Jurassic Park film. These knobs and spikes were homologous to those on 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 may have occasionally eaten insects and small vertebrates as a dietary supplement in the same way many herbivores do today. 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 since the former being larger than the latter, its body might have had an overall stockier frame. Maybe the body of Pachycephalosaurus was more similar to the robust body of Psittacosaurus than to the slim body of Stegoceras.

As one of the most recent groups of dinosaurs identified in formal dinosaur classification, pachys never appear in the oldest works. The ur-example was the 1956 novel A Gun for a Dinosaur, but one of the most popular ones was The Land Before Time in 1988, where the pachy shows up as an aggressive creature 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 hypothesized they lived in mountain habitats just like the bighorn sheep as an explanation for their rarity in the fossil record (mountains do not preserve fossils well). However, the mountain-living hypothesis is not much followed today, as pachycephalosaurian remains have been found mixed together with the other Late Cretaceous dinosaurs.

In the 2000s, scientists found that the smooth domes of the pachys' skulls would have slipped if they struck against each other, and proposed that pachycephalosaurians bashed each other's sides and hips instead. But even this has been disputed, as additional studies seemed to show that their necks were weaker than traditionally thought, maybe not able to withstand such an impact. This led some scientists to think pachycephalosaurs simply used their dome heads to display maturity like an oversized toucan bill. But a 2013 study found healed injuries in multiple pachycephalosaur domes, suggesting that they were used for headbutting and/or flankbutting after all. This was further supported by computer models demonstrating that the skulls of pachys could withstand much higher levels of force than previously thought, over 1500 pounds or the same amount as two NFL players slamming into each other. This doesn't rule out display entirely however; the the domes were made of a unique fibrous tissue that could have supported brightly colored skin when alive. This same tissue also allowed for quick healing from injuries sustained in fights.

The large Pachycephalosaurus was once the only "bonehead" portrayed in fiction. This changed in the 2000s when two smaller relatives, "Stygimoloch" and "Dracorex" started making occasional appearances as well, thanks to their even spikier heads. These two North American pachycephalosaurian genera have gained quite striking names: Stygimoloch spinifer and Dracorex hogwartsia. The former means "Spiny Devil from the River Styx", the latter "Hogwarts' Dragon King". Both lived in the USA alongside Pachycephalosaurus and, like most pachys, are known only from one skull or little more. "Stygimoloch" was discovered in The '80s: it was Stegoceras-sized and is the only known pachycephalosaur with spikes that developed into true horns, with its dome being tall and narrow (one synonym of it was "Stenotholus", "narrow head"). Meanwhile, "Dracorex" was found only in 2006: it was of similar size, had an almost-as-spiky skull coupled this time with a flat, dome-less head.

But in 2009, it was suggested that these two horned pachys were just juvenile Pachycephalosaurus, as not only are all three from the same time and place, but "Stygi" and "Draco" are only known from juveniles whereas "Pachy" is only known from adults. The idea was that the “devil” and the “dragon” represent the subadult and immature growth stages of the fully mature Pachycephalosaurus. Others have thought Pachycephalosaurus proper and "Stygimoloch" are males of different age, and "Dracorex" a young female, basing upon the flat head. While the idea of Dracorex being a juvenile "Pachy" has more or less been fully accepted, "Stygimoloch" still has its supporters, with a few even suggesting it to be a second species of Pachycephalosaurus, P. spinifer, as "Stygi" is known from younger rocks than P. wyomingensis. It may even represent its evolved descendant, in the same way Triceratops comes in the earlier horridus and later prorsus forms (one may also be reminded to the Triceratops-Torosaurus debacle that started just a year later in 2010). This wouldn't be the first time a differences between the adults and juveniles of a dinosaur led people to believe they were different genera; T. rex was originally thought to have a pygmy relative called Nanotyrannus until it turned out young T. rexes were just built different from the adults.

Anyway, "Stygimoloch spinifer" did get a memorable scene in Jurassic World: Fallen Kingdom; it's worth noting that film consultant Jack Horner advised against featuring the "Stygi" due to the above controversy, but was overruled by the filmmakers. But its first apparition in cinema is in 2000's Disney's Dinosaur. "Dracorex hogwartsia", meanwhile, is one of the few real nonbird dinosaurs portrayed in the TV series Primeval, even though in a quite fanciful way, with an actual dragon-like crest on its back. Pachycephalosaurus also showed up in the second season of Prehistoric Planet, using its famous dome to show off to rivals before engaging in a fight that's equal parts headbutting and flankbutting. The episode ends with the showrunners explaining how the current evidence suggests that the animal did indeed butt heads in the manner depicted.

1. Entry Time: 1956 (Pachycephalosaurus); 2000 ("Stygimoloch"); 2006 ("Dracorex")
2. Trope Maker: The novel A Gun for a Dinosaur (Pachycephalosaurus); Disney's Dinosaur ("Stygimoloch"); Primeval ("Dracorex")

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 the stock-role in the pop-consciousness. Stegoceras matches perfectly with all this, being the most abundant, complete, well-known, and even the first discovered dinosaur within its group by far. At 2.5 m long, Stegoceras ("horned roof", because its dome was first mistaken for the base of a horn) 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. It was discovered in year 1924, but was 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 discovery of Pachycephalosaurus twenty years later. As a pachy, “the other Stego” was a small, two-legged animal with a heavy head and the “body armor” limited to its skull. Some alleged Stegoceras remains were once putatively announced in China, but they are now thought to pertain to other dinosaurs. Some have also speculated that the Stegoceras was sexually dimorphic, and one putatively female skull with a slightly less-thick skull-roof was once assigned to its own genus, "Ornatotholus" ("ornated dome").

"The other Stego" also has 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 of being used as a model for the rest of its group: when you see the body, legs, arms, neck and tail of a pachycephalosaur in a book or movie, 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 info about its possible lifestyle, see Pachycephalosaurus above.

1. Entry Time: 1956
2. Trope Maker: The novel A Gun for a Dinosaur (indirectly, as the model for the pachycephalosaurs' body)

Dome-Head and Flat-Head: Prenocephale & Homalocephale *

Pachycephalosaurs are very rare things. Few species have been described so far, all from the Late Cretaceous,^note Alleged pachycephalosaurians from the Jurassic and Early Cretaceous, such as Ferganocephale and Yaverlandia, have all turned out to be from other groups of dinosaurs. and they are all either North American, or Asian^note The Malagasy theropod Majungasaurus was once identified as a pachycephalosaur called "Majungatholus". While the North American ones are more spectacular (Pachycephalosaurus), or more abundant (Stegoceras), the Asian ones are nonetheless very interesting; the two most classic ones were both discovered in the 1970s in Mongolia. Their names make a sort of pun if pronounced together: Prenocephale and Homalocephale. Prenocephale prenes aptly means “prominent head”; it was very similar to Stegoceras, size included, but had a shorter snout, different tubercles, and a higher dome. Like most boneheaded dinosaurs, only skull material is known, but its first skull is so well preserved that even osseous canals for the passage of blood vessels are distinguishable! Some alleged Prenocephale remains were also found in North America, but these now go by different names, like Sphaerotholus and Foraminacephale.

Pachycephalosaurians used to be divided into two main families, Pachycephalosauridae (those with domed heads) and Homalocephalidae (the ones with flat heads). A third less-known family from the Late Jurassic, Chaoyangsauridae, is now known to be the most basal of the ceratopsian lineage. Today, this distinction is not recognized anymore: the flat-headed kinds are actually identical to the bulge-headed ones except for the shape of their skull, and now one single family of pachycephalosaurs is recognized, Pachycephalosauridae. The traditionally most-known "flathead" among the pachys is Homalocephale calathocercos. Homalocephale was similar to Stegoceras in size and shape, and is known from several pieces of its skeleton other than the skull, but not complete remains.

The name Homalocephale means flat head, and with reason: it has indeed a flat head, making it very unpachycephalosaur-looking, rather similar at a first glance to a Hypsilophodon. Actually, its skull structure was clearly pachycephalosaurian, with a slightly thickened skull-roof and bony tubercles very similar to those of Prenocephale. It seems this unusual skull was not adapted for headbutting, but rather for head-shoving, with males simply pushing against each other in contests of strength. Much like with "Dracorex" and Pachycephalosaurus, the similarities to Prenocephale have led to the hypothesis that Homalocephale just the juvenile form of the former, with a not-yet developed dome, especially since they lived in the same time and place. However, the existence of juvenile specimens of Prenocephale suggest otherwise.

The unusual wideness of the Homalocephale pelvis has also led to speculation about possible viviparity (aka giving birth to live offspring). There is no proof of this, as well as in every other non-avian dinosaur: remember that modern dinosaurs (birds) and their closest relatives (crocs and turtles) are all egg-laying animals, while live-bearers among the modern Amniotes are known only from therian mammals (placentals and marsupials) and some lizards and snakes.

1. Entry Time: undetermined
2. Trope Maker: Dinosaur Planet (Prenocephale); its status as "the flat-headed pachy" (Homalocephale)

Other pachycephalosaurians

Sorry, these aren't here. If you're looking for Goyocephale, Tylocephale, Alaskacephale, Sinocephale, 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 the Middle Jurassic to the Late Cretaceous. The smallest ones were slender, completely bipedal, and possibly omnivorous. The more evolved ones became bigger and returned to partial quadrupedality, as well as becoming strict herbivores. The largest were among the most massive non-sauropod dinosaurs. "Ornithopod" means "bird-foot": they had limbs and feet similar to but (ironically) less bird-like than those of the theropods. Unlike the latter, they had small mouth openings and blunt teeth for grinding plant matter. Ornithopods are the most abundant dinosaurs in the fossil record, and as such are often portrayed as inoffensive herd-living animals akin to deer and antelope. Even though they lacked the thick defenses of the armored 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, but 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 many 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 archetype of the group, Hadrosaurus. Breaking the usual rule, none of them is the biggest known hadrosaur. Hypacrosaurus, Tsintaosaurus, and Shantungosaurus are rather common in documentary media, while Parasaurolophus and Edmontosaurus have always contended for the record of the most iconic duckbill.

An Instrument for Trumpeting: Parasaurolophus ***

Walker's Almost Saurolophus

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

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 the "chosen prey" for tyrannosaurs, "raptors", and giant crocodiles, incapable of offering resistance 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 were associated with water in pre-Renaissance times. Indeed, the sauropods and the hadrosaurs were once considered the two amphibian lineages of dinosaurs — all the other dinosaurs were considered adapted for a land-living style. Why? Because the early discovery of some mummified hadrosaurs whose skin on their hands was believed to be remnants of webbing made scientists believe they were semi-aquatic creatures with literally duck-like webbed hands — not because they were thought too heavy to sustain their bulk on land, unlike the giant sauropods. 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, and their duck-like qualities are often played up (see the tellingly-named Ducky from 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 would flee into the water to escape the less able giant theropods. Later research seems to indicate that hadrosaurs were no more accomplished swimmers than any other dinosaurs were, and that tyrannosaurs were probably just as capable of swimming as any other land animal was (ostriches can swim pretty well, and they don't have arms for paddling). Really, a lot of the bias regarding hadrosaurs as being exceptional swimmers or semi-aquatic has to do with the fact they are nicknamed "duckbills", naturally leading many to think of them in comparison to modern-day waterfowl.

Specifically regarding Parasaurolophus, countless hypotheses have been made about the function of its "horn": among them, a tool to thread its way through dense forest foliage, or 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 the sound box of an instrument. Scientists have even been able 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 usually in minor roles — basically with the sole purpose of increasing the variety of the "dinosaur world". And don’t expect to hear its name, either — even though it's not one of the shortest dino-names, it remains cool-sounding anyway. A good example is in the Jurassic Park films. Some Parasaurolophus are visible behind the Brachiosaurus in the famous "Welcome to Jurassic Park!" scene of the first film; they are also seen in every following sequel, too. But all these were simple cameos, and the animal is never named in dialogue - one character does make an attempt in the second movie, but gives up fairly quickly. Other unnamed appearances are in Disney movies — Fantasia (where they have the old upright pose and a huge flap of skin between the crest and the neck) and Dinosaur (where they are more modern-looking). 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 based on its distant relative Saurolophus.

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

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

Regal Edmonton Lizard and Connected Edmonton Lizard (or Connected Duck Lizard if they are not the same)

No other Stock Dinosaur has had such a Mind Screw story as Edmontosaurus/Trachodon/Anatosaurus/Anatotitan: the Brontosaurus/Apatosaurus story is nothing in comparison. Here, Science Marches On to an insane degree, coupled with huge Taxonomic Term Confusion and I Have Many Names. This hadrosaur roamed North America at the very end of the Cretaceous, 73-66 mya. Three species in two genera were recognized since The '90s, Anatotitan copei, Edmontosaurus annectens, and Edmontosaurus regalis, but A. copei was merged into E. annectens in 2011. Some claim this makes Edmontosaurus the only valid name for this dinosaur, while others support the separation of E. annectens as Anatosaurus annectens. By any name, these creatures were some of the biggest hadrosaurs, reaching up to 12 m long — as long as T. rex and a bit heavier than it. Despite this, their size didn't preclude them from being among the rex's favorite prey, with numerous specimens having T. rex bite marks on them, including several healed injuries that tell us they survived T. rex predation attempts. But like modern-day carnivores, it is likely that rex more often attacked the young, sick, injured and dying than the healthy adults. T. rex would have specifically hunted Edmontosaurus/Anatosaurus annectens, which lived alongside it 68-66 mya, whereas Edmontosaurus regalis (Edmontosaurus sensu stricto) lived earlier, about 73-70 mya alongside the smaller Albertosaurus. A third currently unnamed species, previously identified as it own dinosaur called Ugrunaaluk, lived in Alaska about 70-68 mya alongside Pachyrhinosaurus and Nanuqsaurus.

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

Edmontosaurus/Anatosaurus annectens deserves the "duck-billed dinosaur" title more than any other hadrosaur, with its very flat head and spatula-like beak. Edmontosaurus regalis (Edmontosaurus sensu stricto) had a stockier head and 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 works, 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 able to grind the toughest vegetation (fossil pine needles have been found in the aforementioned mummies), giving them the highest number of teeth for any land vertebrate that has ever lived.

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 both species of Edmontosaurus have been considered the crest-less hadrosaurs par excellence, because their skull didn't show any bony prominence; but science marched on in 2013 and a specimen of Edmontosaurus regalis was discovered to have had a small, fleshy cockscomb on its head; this thing was discovered only thanks to the petrified soft tissues found — maybe other "crestless" dinosaurs had some sort of fleshy protrusions on their head. After all, a chicken skeleton doesn't show sign of their fleshy crest and appendages. However, we're still not sure if Edmontosaurus/Anatosaurus annectens had the same crest, so most reconstructions forgo it to further differentiate it from E. regalis.

Here’s a brief summary of Edmontosaurus' awesome taxonomic tangle. The first remains, isolated teeth found in the 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 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 could 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 to Edmontosaurus annectens ("swimming Edmonton's lizard"). At this point the copei was the only remaining Anatosaurus, but... taxonomic rules say "Anatosaurus" should indicate only the annectens. This meant it should be renamed, too. Since scientists are often very nostalgic, they decided to recall it with a similar name: Anatotitan ("giant duck"). And then in 2011, Anatotitan was determined to be a fully grown Edmontosaurus annectens and thus sunk into Edmontosaurus^note Compare to the Dracorex/Stygimoloch/Pachycephalosaurus and Triceratops/Torosaurus stories above. And that leaves us in the present with just the younger, larger Edmontosaurusa annectens and the older, smaller Edmontosaurus regalis, although some scientists suggest the former should become Anatosaurus annectens again. Quite simple, isn’t it?

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

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

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

The Good-Mother: Maiasaura **

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

Hundreds of Maiasauras were discovered together in Montana in 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 appearances), 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 a few dinosaurian eggs were known to science: those of Protoceratops, oviraptorids, "Hypselosaurus", Psittacosaurus, and a 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 themselves? Here is the proof of parental care: only adult Maiasaura could have fed the young such plant matter until they grew large enough to finally leave their nest. Horner gave a Meaningful Name to his caring dinosaur: Maiasaura peeblesorum means "Peebles' good mother lizard" (note the unusual feminine suffix -saura). It was his deep study of this dinosaur and its parenting habits that gave Horner his prestige in the scientific community.

Horner and other scientists have since made a possible reconstruction of the Maiasaura lifestyle. Huge herds of possibly up to 10,000 individuals used to migrate across Western North America from Canada to Montana for wintering at their nesting islands. Here, they mated, built their nests, laid their eggs, and filled their nests with decaying vegetation to keep the precious eggs warm: remains of fossilized rotting plant material have been found in these nests (adult Maiasaura were too heavy to sit on their eggs like modern chickens do.) After the hatching, adults fed their helpless babies good food, moved by their cute appearance: the babies’ skulls show large eyes and short muzzles like modern mammal cubs. After developing their skeletons, the youngsters started to search for food on their own; finally, the whole herd undertook again their migration once more. In short, an overall behaviour very similar to many modern migrating birds.

This reconstruction made the top of the Dinosaur Renaissance, definitively debunking the old big, stupid, unfeeling, oafs thing, and making Maiasaura just as common in popular books as Parasaurolophus and Edmontosaurus. However, Maiasauras inconspicuous appearance was not interesting enough to earn it any movie appearances. Even though the "good mother dinosaur" and the whole argument around are often mentioned in the first Jurassic Park novel (which, by the way, had Horner as the consultant), this was totally overlooked in Steven Spielberg's following film. However, Maiasauras impact was still felt across other dinosaur portrayals. In The Land Before Time for instance, all the herbivorous dinosaurs migrate through the lands and hatch their young in crater-like nests made of earth. In reality, evidence suggests some dinosaur groups, like the sauropods, did not take care of their young at all, and other would have likely practiced different styles of parenting. However, our knowledge of dinosaur parenting in most groups is still incomplete and a lot of their behaviors remain speculative.

In The New '10s, Maiasaura finally made its first movie 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 that, the Maiasaura had also appeared on teleivison in Dinosaur Planet (as one of the protagonists alongside the tyrannosaur Daspletosaurus), as well as an episode of The Magic School Bus (as one of the dinosaurs encountered by Ms. Frizzle and her students on a Time Travel field trip to Late Cretaceous North America).

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

Big Round Crest: Corythosaurus **

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

Corythosaurus was slightly smaller than Parasaurolophus (7-9 m long), and lived in Late Cretaceous North America about 77-75 mya. A classic error in paleo-art is to depict these two dinosaurs living alongside Tyrannosaurus rex. Since the "rex" was discovered in more recent terrains (68-66 mya), this makes a slight Anachronism Stew case. More accurate works might depict these two animals being menaced by smaller, earlier tyrannosaurids like Daspletosaurus or Gorgosaurus.

First discovered in 1912 by Barnum Brown (who is also known for having found the very first Tyrannosaurus skeletons in Montana about a decade earlier), the "corytho", unlike the "para", has one of the richest fossil records among hadrosaurs. Several complete specimens are known to science, including many juveniles. The corythosaur’s cranial structure was similar to the parasaur's, with a relatively narrow duckbill compared with Edmontosaurus and expanded nasal bones that formed a crest. However, the Corythosaurus crest was very different than that of Parasaurolophus: it was laterally-flattened, round-shaped, and put upright above the head. Its 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 to be both very different-sized and very 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. In fact, these differences initially led scientists to believe them to all be different genera of dinosaurs under such names.

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 proper comparison. Since hadrosaurian crests are so differently-shaped, experts have concluded that they also had the function of visually distinguishing 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 youngsters. Just as French horns and bassoons have a different timbre, so would Corythosaurus and Parasaurolophus.

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

Giant Hadrosaurs: Lambeosaurus & Shantungosaurus *

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

Traditionally, two hadrosaurs have contended for the record: the crested North American Lambeosaurus (namesake of the lambeosaurines) and crestless Chinese saurolophine Shantungosaurus. Lambeosaurus ("Lawrence Lambe's lizard"), one of the most striking-looking hadrosaurs, also has a rich fossil record, with two distinct species described. A third species was originally described, but was reclassified in 2012 as a brand new genus, Magnapaulia.

Overall, Lambeosaurus was similar to Corythosaurus with a flat, vertical crest with the same hollow spaces. However, the crest of the best 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 a 90° angle 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 slightly forwards like a pomapadour. Magnapaulia laticaudus (formerly "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, nearly twice the weight of a large Tyrannosaurus rex like the famous Sue. In contrast, the two confirmed species of Lambeosaurus 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.

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

1. Entry Time: 1990s (Lambeosaurus); undetermined for Shantungosaurus
2. Trope Maker: Dinotopia (Lambeosaurus); its status as the biggest hadrosaur (Shantungosaurus)

USA and China make Peace: Saurolophus *

In general, Late Cretaceous dinosaurs in Western North America are very similar to those in Eastern Asia. This is because these landmasses were joined at the time by a stripe of dryland where the Bering Strait is today. This means that dinosaurs at the time could wander from one continent to another. But even though many groups of dinosaurs are shared between both continents (pachycephalosaurians, ornithomimosaurs, oviraptorosaurs, tyrannosaurids, ankylosaurids, and ceratopsians, to name a few), Asian and North American dinosaurs are usually classified as distinct genera: see Tyrannosaurus rex and Tarbosaurus bataar for example.

But there is 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 many more specimens were discovered in the Gobi Desert 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, the North American species, Saurolophus osborni ("Osborn's crested lizard") has also been important. 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 instead of downwards, and really was horn-shaped; but as a saurolophine, the crest of Saurolophus made by solid bone and not hollow like that of the Parasaurolophus. And if you're wondering about the name, yes, Saurolophus was the namesake of the saurolophines.

The two “horned” duckbills tend to be confused with each other by non-specialists — and their similar names don’t exactly help to resolve the mix-up. 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 a Parasaurolophus. Ironically, as a saurolophine, Saurolophus was closer to crestless hadrosaurs like Edmontosaurus than to Parasaurolophus! Also of interest is that Saurolophus and its kin have often been depicted in paleo-art with a speculative, inflatable, frog-like air-sac on its snout, although there is no hard proof for this. This air-sac was conceived as a mean to amplify sounds just like the hollow crests of Corythosaurus and Parasaurolophus.

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

Taxonomy Confusions: Hypacrosaurus & Tsintaosaurus *

If you see a “frisbee”-crested hadrosaur in books or documentaries, don't assume it’s Corythosaurus. The latter had a "twin" called Hypacrosaurus altispinus, with a similar crest though fairly smaller, wider, and pointed on the top. Sadly, since some (possibly female) Corythosaurus also have a rather low crest, this doesn’t help us so much to differentiate the two; the surest trait to do it is to spot the taller neural spines of Hypacrosaurus in a mount (altispinus means "tall-spined"). Not surprisingly, Hypacrosaurus has been confused with Corythosaurus or even Lambeosaurus in the past, and to complicate matters, some juvenile remains from these three animals were even labeled as two genera on their own, "Cheneosaurus" and "Procheneosaurus"!

Hypacrosaurus was, notably, the last of the lambeosaurines to live in North America, with its most recent fossils dating back to the time just before T. rex and Triceratops showed upon the scene. So while it may not have been around to be hunted by the rex, it did coexist with dinosaurs like Anchiceratops, Arrhinoceratops, Pachyrhinosaurus, (see the ceratopsians folder above) and the previously mentioned Edmontosaurus regalis and Saurolophus — all preyed upon by Albertosaurus. That being said, some very Hypacrosaurus-like remains have been found in the Ojo Alamo formation dating back to the very end of the Cretaceous 66 million years ago, suggesting that it or a close relative may have survived all the way up to the mass extinction. In the nineties, a nidification site in North America full of Hypacrosaurus nests and hatchlings has been discovered, similar to Maiasaura; this find has made Hypacrosaurus a much more well-understood duckbill among scientists.

Nicknamed the “unicorn dinosaur”, the lambeosaurine Tsintaosaurus spinorhinus ("spiny-nosed Tsing-Tao lizard") was found in the 1940s by famed Chinese paleontologist Yang Chung-chien (or C.C. Young) like the sauropod Mamenchisaurus, and thus is one of the “classic” Chinese dinosaurs.

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

1. Entry Time: the 1990s
2. Trope Maker: the issues about their crests

The Decayed Nobleman: Kritosaurus & Gryposaurus *

Most of the North American hadrosaurs were described at the beginning of the 20th century, in the second memorable “Dino-Rush” led in North America. Among them, one of the most historically relevant has been the saurolophine Kritosaurus, found in New Mexico (most of the others were found in Alberta). Other than the skull, saurolophines 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 Hadrosaur 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, after the Navajo people.

Then, Science Marches On hit hard on this duckbill. In the 1990s, additional specimens from Alberta were reclassified as Gryposaurus (which had been previously sunk into Kritosaurus after its initial description in the 1910s), taking with them the best skull material showing the classic bulge that once pertained to the kritosaur. To worsen things, the genus Kritosaurus has revealed to be a wastebasket taxon, and most of its former remains are either now of uncertain attribution or considered new dinosaurs like Anasazisaurus or Naashoibitosaurus — some labelled "K. australis" in the 70s were found in an unusual location for duckbills, South America, and now go by Huallasaurus. While Kritosaurus remains a valid genus today, it has now become poorly understood just like Hadrosaurus (below), and we even don’t know if the kritosaur really had the classic bump on its nose. Nowadays, Gryposaurus, the new owner of the skulls previously attributed to Kritosaurus, 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 (Kritosaurus); 1990s (Gryposaurus)
2. Trope Maker: Fantasia (Kritosaurus/Gryposaurus)

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.

Hadrosaurus was the very first dinosaur ever identified as such in North America (and outside of Europe) from more remains than simple isolated teeth, as early as in year 1858. Like most early discoveries, Hadrosaurus has a generic-meaning name, “heavy lizard”. Oddly for a US dinosaur, it was found in New Jersey — dinosaur remains are extremely rare east of the Mississippi. However, dino discoveries in the States began on the East Coast, and it was only with the start of the Bone Wars - sometimes called the Great Dinosaur Rush - that the American West become more important.

Hadrosaurus foulkii (William Foulke was the one who first found its bones) was already recognized as an Iguanodon relative, but the latter was still depicted as totally quadrupedal at the time. Hadrosaurus remains, though very incomplete, clearly showed an at least partly bipedal creature. Joseph Leidy (its namer and the so-called father of American paleontology) was the first paleontologist to have described a large-sized dinosaur in the classic upright posture: a revolutionary idea at the time that only became more popular later.

Hadrosaurus also has the distinction of being 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 practically unknown, so Leidy didn’t understand that he was 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. Hadrosaurus was originally believed to be a saurolophine, and at the time, the group was known as "hadrosaurines" after it, but later studies revealed it to be a much more primitive animal outside of the two subfamilies and instead near the base of the hadrosaurid family tree - this in turn led to the "hadrosaurines" being renamed the saurolophines.

Hadrosaurus was the animal originally chosen by Michael Crichton for the "stampede scene" in his original Jurassic Park novel, while Spielberg's following film chose to substitute it with the ornithomimosaur Gallimimus. Hadrosaurus is occasionally confused with Edmontosaurus in popular non-fictional representations due to their superficial similarities, but you can also sometimes hear the Hadrosaurus name being used in pop culture for all hadrosaurs as a result of confusion between the specific animal Hadrosaurus and the general term "hadrosaur".

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

Other hadrosaurs

Sorry, these ones aren't here. If you're looking for Prosaurolophus, Secernosaurus, Brachylophosaurus, Amurosaurus, Olorotitan, Charonosaurus, Telmatosaurus, Tethyshadros, Velafrons, Claosaurus, Mandschurosaurus, 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 from Early Cretaceous Europe. And if you're even luckier you might see the Late Jurassic Camptosaurus, Dryosaurus, and Nanosaurus, the first similar to Iguanodon and the other two to Hypsilophodon. Also worthy of note are Tenontosaurus and Ouranosaurus because are they are strongly associated with one famous predatory dinosaur each (Deinonychus and Spinosaurus respectively; albeit for different reasons). Muttaburrasaurus and Leaellynasaura are known for being rare examples of Australian dinosaurs, while Thescelosaurus and Orodromeus are the animals that the controversial "petrified heart" and "petrified nests" were attributed to, respectively. Heterodontosaurus, Lesothosaurus, Fabrosaurus, and Scutellosaurus are here for convenience, but are not true ornithopods anymore according to modern knowledge. Iguanodon, Camptosaurus, Dryosaurus, Tenontosaurus, Muttaburrasaurus, and Ouranosaurus are all part of a group of ornithopods known as the iguanodontians, which include the ancestors of the hadrosaurs. Meanwhile, Hypsilophodon, Leaellynasaura, Orodromeus, Thescelosaurus and tiny Nanosaurus once formed a group called the "hypsilophodonts", but are now considered to be a miscellany of extremely primitive ornithopods or even basal ornithschians and not true ornithopods at all.

The Veteran of the Dinosaurs: Iguanodon ***

Bernissart's Iguana Tooth.

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

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

Unlike the hadrosaurs, Iguanodons most distinctive traits are in its hands, not its head. The best known of these is the spiked thumb, made of the first digit's phalanxes fused together and encapsulated in a horny sheath, usually shown in books as a weak weapon against enemies. It also had a very flexible, opposable "pinkie" finger, maybe to grasp vegetation. Hadrosaurs too had a little-finger in their hands other than the three main digits, but it was smaller than the Iguanodons one and maybe useless and vestigial. Like hadrosaurs, the three central fingers of Iguanodon were fused together in a hoof-like structure and supported the weight of the dinosaur when on four legs, though incorrect freely-fingered iguanodonts and hadrosaurs often appear in portrayals.

We don’t know for sure if iguanodonts and hadrosaurs were mainly tree-browsers or ground-grazers. However, classic portraits usually show iguanodonts in the usual "tripodal" stance and browsing like a giraffe. Some paleoart has 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 a horsey head, robust clawed forelimbs, a giraffe-like tongue, and a tail used as a tripod together with the hindlegs.

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

Most dinosaurs have changed their look at least once: Iguanodon has done this twice. The first attempt at reconstruction showed a huge dragon-like quadruped, and one of its thumbspikes was inaccurately put on its nose — an understandable mistake, given the very fragmentary nature of its original remains. The life-sized Iguanodon, alongside Megalosaurus, Hylaeosaurus, and other extinct animals (including Ice Age megafauna, marine reptiles, and pterosaurs), were sculpted by Benjamin Waterhouse Hawkings and shown to the public during the 1856 Universal Exposition in London, at the famous Crystal Palace. A banquet was organized to celebrate the event... inside the still incomplete iguanodon model! Even though the palace was ultimately destroyed by a fire, the sculptures survived, and the Crystal Palace Dinosaurs are still there for all to see.

After the discovery of the complete skeletons from the Belgan "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 1970s and led by English paleontologist David Norman made Iguanodon quadrupedal again (though still capable of standing and running on two legs), with cheeks hiding the teeth in the living animal.^note Once, all ornithischian dinosaurs were portrayed with no cheeks and a wide mouth running from ear to ear, like saurischian dinosaurs: this was based on modern reptiles, which are invariably cheek-less. The shape of ornithischian jaws showed they could have had cheeks to store plant matter during mastication, like modern herbivorous mammals. Thwas is confirmed by the "hadrosaur mummies." If alive today, an ornithischian’s head would resemble a hairless ungulate with a beak. 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 always on all fours like an actual horse.

Even though it has been extremely common in dinosaur books and other non-fictional media, Iguanodon did not make any significative apparitions in cinema or TV before Disney's Dinosaur and Walking with Dinosaurs were broadcast during the 20th-21st century change. The most recent one is in 2022's Jurassic World Dominion. Rule of Cool easily explains why: with its generic look and weak weapons, it doesn’t bear comparison with Tyrannosaurus rex jaws, Triceratops horns, Stegosaurus or Ankylosaurus armour and weaponized tails, "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 inconspicuous. However, its historical and scientific importance remain 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 Disneyfied horses.

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

Tree-Climber or Ground-Runner?: Hypsilophodon **

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

One of the first dinosaurs discovered, way back in 1849, it 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 of complete individuals have been found, and this also explains its historical role as the stock small ornithopod. Most remains come from England, especially the southern Isle of Wight, home of many other Early Cretaceous English dinosaurs, but some uncertain remains attributed to Hypsilophodon come from North America and Spain.

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

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

Before the 1970s, Hypsilophodon was believed to be 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 sometimes even fiction. This is how it is shown, for example, in Fantasia— the tiny, green tree-climbing dinosaurs that the Stegosaurus disturbs are Hypsilophodon. Few other dinosaurs have had such a great Science Marches On story: maybe only Spinosaurus, Megalosaurus and Iguanodon can rival it in this area. While Iguanodon was often reconstructed using a classical kangaroo as a model, Hypsilophodon was often compared with the tree kangaroo.

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, especially the toothless ones. Hypsilophodonts are often cited with ornithomimids as examples of harmless dinos: ostrich-dinosaurs too had a graceful appearance, large eyes, and were fast runners, but are more strongly associated with birds in public mind than the small ornithopods like Hypsilophodon (and were also closely related to them). A singular case is in The Land Before Time 3, 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 to the protagonistic Five-Man Band.

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 further paleo-artistic depictions of "hypsies". As the picture was from 1985, the animal is shown scaly; today many scientists think it was covered by feather-like structures, like other small ornithischians.

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

The Wildebeest of the Jurassic: Camptosaurus *

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 the 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 to a natural science museum and the first dinosaur skeleton they see belongs to a juvenile Camptosaurus. But when was the last time you saw it in documentaries other than Planet Dinosaur, which portrays it as a simple fodder for the allosaurs?

Camptosaurus lived in Late Jurassic North America just alongside Brontosaurus, Diplodocus, Brachiosaurus, Stegosaurus, and indeed Allosaurus: it could have shown up in 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 judged as too inconspicuous to capture the watchers’ interest. Other two very important Late Jurassic North American 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 Iguanodon and the hadrosaurs: indeed, Camptosaurus was one of the most primitive big ornithopods and one of the most basal thumb-spiked iguanodontians (properly known as ankylopollexians, meaning "hooked thumbs"). In the Jurassic world still dominated by sauropods, camptosaurids and stegosaurians were the only big ornithischians that were successful, anticipating the great diversity bird-hipped dinosaurs reached later in the Cretaceous.

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

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

The Gazelles of the Jurassic: Dryosaurus & Nanosaurus *

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 that Camptosaurus didn't, all made around the Turn of the Millennium, though with very minor roles — in one case, it serves only as prey to Allosaurus — but it doesn't appear in 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 iguanodontian and not related to Hypsilophodon, and the prototype of its own lineage, the Dryosaurids. It was once considered a big "hypsilophodont", as big as the Late Cretaceous Thescelosaurus, but "hypsoliphodont" is no longer considered an actual group, rather a motley collection of miscellaneous small ornithopods and basal ornithischians.

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 — but have since been re-classified as their own dinosaur, Dysalotosaurus. Other alleged Dryosaurus were found in Early Cretaceous Europe, but now go by Valdosaurus.

Camptosaurus and Dryosaurus are very frequently portrayed in dinosaur books, especially the former; here both are typically shown as among the favorite prey of Allosaurus and 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 on two legs as fast as they could. Dryosaurids, being smaller and more maneuverable, were probably faster than camptosaurids, but the latter, being bigger and stronger, 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.

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

Much like Camptosaurus and Dryosaurus, Nanosaurus doesn't get a lot of spotlight when it comes to Late Jurassic North American dinosaurs; between the Walking with... series, Planet Dinosaur, and When Dinosaurs Roamed America, it only appears in the first one under the Othnielia name — unnamed in the Late Jurassic focus episode and as a background critter in the Ballad of Big Al special. But also like the two Late Jurassic North American ornithopods, it tends to appear a lot in dinosaur books, usually under the Othnielia name, making it the most recognized of all its many names. But today, it is no longer considered "the smallest North American dinosaur" — that record now pertains to a tiny heterodontosaurid found only in 2009, Fruitadens, another inhabitant of Late Jurassic North America and a neighbor of the abovementioned ornithopods, as well as the famous sauropods, stegosaurs, and theropods.

1. Entry Time: 1999
2. Trope Maker: Walking with Dinosaurs and sequels (both)

Beware My Long Tail: Tenontosaurus *

One of the most iconic scenes in paleo-artistic works made during the 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. Unlike the latter, the tenontosaur was totally devoid of thumbspikes, being more basal than the ankylopollexian iguanodontians (just like Dryosaurus was). And also like the dryosaur, it was once considered an overgrown "hypsilophodont" — more precisely, the biggest member of the group by far. It had long front limbs (classic portrayals often show it quadrupedal) with five digits each, a long neck, a small head, and the primitive four-fingered hindfeet of basal ornithopods, but its most distinctive trait was surely its tail. Its tail was much longer than in most other relatives, twice the length of the rest of its body, and often depicted as a sort of "whip", almost like the tail of a diplodocid sauropod — but it could have actually been more rigid than often shown.

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 consider the idea of these predators as wolf-like pack-hunters capable of bring down larger prey with their agility and their sickle-claws; Tenontosaurus has thus given indirectly contribute to the modern public image of dinosaurs as fast, intelligent, and dynamic animals.

In these struggles, Tenontosaurus is usually shown swinging its enormous tail and hitting some “raptors”, 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). In fact, since the original Tenontosaurus discovery, 20% of all tenontosaur fossils have been found in association with Deinonychus and 14 of the 50 fossil sites Tenontosaurus is known from have also produced Deinonychus remains. And on Deinonychus' side, only 6 Deinonychus fossil sites lack Tenontosaurus. Clearly, there was some kind of predator-prey relationship between the two.

But as discussed in our entry on raptors, the idea that raptors hunted in packs has been called into question by some scientists, who point out that neither birds nor crocodiles do this. Thus, it's been suggested that maybe the Dinonychus were simply scavenging on the carcass of a Tenontosaurus they found already dead, with the presence of their skeletons around the herbivore just being of those who were killed in squabbles over the choicest parts — the same happens today when Komodo dragons gather around a dead water buffalo. Its important to note however that most of the Tenontosaurus found with Deinonychusremains around them were juveniles, so it seems that Deinonychus, pack-hunter or not, generally avoided fully grown individuals. Adults however would have had to worry about Acrocanthosaurus, the apex predator of the day.

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 Deinonychus is the real identity of the chosen raptor in the story. The "tenonto" also appears in Jurassic Fight Club as the victim of a pack of Deinonychus, naturally. 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

The Gazelles of the Cretaceous: Thescelosaurus & Orodromeus *

Hypsilophodon, Dryosaurus, Nanosaurus, and Tenontosaurus, the three traditionally most-known "hypsilophodonts", were Late Jurassic or Early Cretaceous; but Hypsilophodon-like animals also existed in the Late Cretaceous, even though they tend to be overshadowed in paleo-art by the spectacular ornithischians of their period: hadrosaurs, ceratopsians, ankylosaurs, and pachycephalosaurs. In North America, while duckbills took the “wildebeest” role, the “gazelle” one was mainly played by the thescelosaurids, named after their most famous member of their group, Thescelosaurus neglectus. Thescelosaurus ("marvelous lizard") was 3-4 m long and lived at the extreme end of the Cretaceous, 68-66 mya, making it a neighbor of Tyrannosaurus rex and Triceratops and one of the very few dinosaurs that managed to see the asteroid at the end of the Dinosaur Era.

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

A Thescelosaurus specimen nicknamed "Willo" is the animal from which the controversial “fossilized heart” comes from. As exciting as the idea of a preserved dinosaur heart sounds, it is almost certainly a fossilization artifact: that is, a piece of stone that just casually resembles a heart. Discovered in 2000, this stony concretion was celebrated by the media as the ultimate proof of “warm-bloodedness” among dinosaurs, because it seemingly showed a four-chambered heart just like bird and mammals and unlike most modern reptiles — crocodilians have four-chambered hearts, but their ancestors could have been warm-blooded as hypothesized in the late 2000s.

There were other thescelosaurids from Late Cretaceous North America that were smaller and lived slightly earlier than Thescelosaurus. The most notable of these was Orodromeus makelai, "Makela's runner of the (Egg) Mountain". It was discovered in Montana in 1988 by Jack Horner and his assistant Robert Makela in the same site in which they had found Maiasaura eight years before. At their site, Horner and Makela noted some small, unusually spiral-shaped nests full of eggs containing fossilized embryos. To small to be from Maiasaura, they attributed these to Orodromeus, and noted that since the bones inside those eggs were already well-formed, the Orodromeus' hatchlings must have been more independent at birth than the Maiasaura ones. Science Marches On however, and later it was found that those eggs/embryos were instead from the theropod Stenonychosaurus (aka Troodon). The ironic thing is that fossils of stenonychosaurs were discovered around those putative Orodromeus nests, but it was thought that they were actually preying on Orodromeus nestlings: an astonishingly similar story to the “Oviraptor robbing Protoceratops eggs” tale some six decades earlier. Orodromeus shows up in Dinosaur Planet being hunted by Stenonychosaurus-as-Troodon.

While not Stock Dinosaurs (or even minor-Stocks), there are some other thescelosaurids we'd like to take note of here. Oryctodromeus ("digging runner"), found in 2007 and living quite a bit earlier than the similar-named Orodromeus (100-94 mya as opposed to 77-75 mya), is notable for showing the first proof of digging behavior among non-avian dinosaurs: its skeleton was found inside a fossilized burrow. A relative found in Alberta known since the start of the 20th century is Parksosaurus ("William Parks' lizard", sometimes misspelled "Parkosaurus"), which was similar in size and shape to Orodromeus but lived about 70-69 mya. Zephyrosaurus ("lizard of the western wind"), lived earlier than all these, in the Early Cretaceous alongside Deinonychus, likely being one of its main prey items.

1. Entry Time: 2000s
2. Trope Maker: the "heart of stone" (Thescelosaurus); Dinosaur Planet (Orodromeus)

Duck-billed Spinosaur: Ouranosaurus *

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

Discovered by a French expedition to Niger led by Philippe Taquet in the 1970s, Ouranosaurus nigeriensis lived in what is today the Sahara Desert, just like Spinosaurus aegyptiacus (which was found a bit further north, 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. Additionally, we need to consider the fact when these dinosaurs were alive, the Sahara was a lush wetland, with Spinosaurus being an amphibious fish-eating dinosaur. Like Spinosaurus, some scientists argue that Ouranosaurus had a fleshy and/or fatty hump instead of a “sail”, because its vertebrae are similar to those of modern bison. But others say that comparing dinosaurs with modern big mammals is not correct, since these are two completely distinct zoological groups. Until we find remains of soft tissues of both dinos, the question will remain unanswered. Interestingly, because of the scarcity of its fossil record (only two individuals were found in the expedition, and nothing more since) some think Ouranosaurus was more solitary than other ornithopods, averting 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 (there was however a relative of Spinosaurus living alongside the ouranosaur, that is Suchomimus; the giant crocodile relative Sarcosuchus also lived alongside both dinosaurs). Just as an example, the Ouranosaurus' one documentary appearance in Planet Dinosaur showed the two living at the same time (Sarcosuchus has the same time-travel problem). 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 wildebeest or zebras — for examples, moose and kudus are known to be rather lonely animals.

In 2021 Ouranosaurus has made its way into fiction, appearing in the third season of Jurassic World: Camp Cretaceous. Here, they are presented as dangerous herd animals, almost like "duck-billed spinosaurs". Before, it is spottable in some of the many sequels to The Land Before Time (The Great Longneck Migration), recognizable thanks to its "sail".

1. Entry Time: undetermined
2. Trope Maker: its "sail" and the association with Spinosaurus

Land Down Under Dinosaurs: Muttaburrasaurus & Leaellynasaura *

If you’ve seen the fifth episode of Walking with Dinosaurs, you’ll already have an idea of who we’re talking about. Many dinosaurs are known today from Africa, from huge Giraffatitan and Carcharodontosaurus to smallish Massospondylus (the most abundant) and Kentrosaurus, to the tiny ornithischians Heterodontosaurus and 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, especially four animals: Muttaburrasaurus langdoni, Leaellynasaura amicagraphica, Minmi paravertebra, and the alleged dwarf polar allosaur (based on a single ankle bone now considered too dubious to readily classify), all from Early Cretaceous East Australia. Muttaburrasaurus is probably the most well-known and portrayed Australian dinosaur in media. Like many Australian fossils, it 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 much more primitive despite having lived slightly more recently (approx. 112 mya). It had different grinding teeth and the primitive four toes for each foot seen in Camptosaurus: it was once believed to be related to the camptosaur, but is now considered to be one of a group of extremely basal iguanodontians called the rhabdodontomorphs.

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

Muttaburrasaurus appeared prominently in Walking with Dinosaurs in the fifth episode "Spirits of the Ice Forest" as the biggest animal of its fauna and with speculative airsacs on its nose to make loud sounds. It also showed up in the third sequel of The Land Before Time (rather incorrectly portrayed, in truth), together with Hypsilophodon and Nodosaurus (see above).

Dinosaur names are often thought of as bizarre-sounding, and Leaellynasaura certainly does match the commonplace very well, like its bigger compatriot Muttaburrasaurus. Leaellynasaura amicagraphica was named after the daughter of its discoverers, Leaellyn. A much more obscure Australian dinosaur, Timimus, was named after Leaellyn's brother, Tim. It has mimus at the end because was originally thought an ornithomimosaur. Leaellynasaura (sometimes misspelled "Leaellynosaura") owes well its feminine suffix saura, just like the hadrosaur Maiasaura which means “good-mother lizard”. First found in 1989, Leaellynasaura was a small (1 m long) bipedal animal similar to Hypsilophodon. Once considered a “hypsilophodont”, the dissolution of this group for its lack of unifying traits except small size had made the classification of this little dinosaur uncertain. Some regard it as a more a more basal ornithischian, but in 2019, it was proposed to be part of a uniquely Southern Hemisphere group of extremely primitive ornithopods known as the Elasmarians, many of which were also formerly classified as "hypsilophodonts". Fossils discovered in Australia in the 2000s indicate presence of a small Early Cretaceous ornithischian with tail 3 times longer that its own body (even more than the Tenontosaurus tail); whether this is the same taxon as Leaellynasaura or not remains to be seen.

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

1. Entry Time: 1999 (both)
2. Trope Maker: Walking with Dinosaurs (both)

A Herbivore with Fangs: Heterodontosaurus **

Among basal ornithischian dinosaurs, there were curious things. Heterodontosaurus tucki, for example, might as well be renamed the "boar-bird".

The "hetero" lived in the Early Jurassic like the armored Scelidosaurus but farther south, in South Africa, 200-190 million years ago. Heterodontosaurus superficially resembled Hypsilophodon with its slender, bipedal body, but was even smaller (1.2m/4ft long), more robust, and with longer forelimbs. As the namesake and archetype of the heterodontosaurids, it was actually one of the "largest" basal ornithischians, despite being only a bit bigger than a Compsognathus. Its skeletons have not left traces of feather-like structures, but since its close relative Tianyulong had 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, analogous to those seen in more evolved ornithischians; and in front of them, the small peg-like teeth only on the tip of the upper jaw, a typical condition of all basal ornithischians. This makes its head as an odd mix of primitive and evolved traits.

We are not sure about what the "hetero" ate in life, because of this specialized dentition. The dominant hypothesis is that Heterodontosaurus was a mostly herbivorous omnivore, eating insects to supplement its usual diet of vegetation, while the "fangs" would have been used for display and/or competition, a bit like in male baboons or musk-deer (thus acting more like "tusks"). Some scientists suspect only males had the large canines like what is seen in some small species of deer, but there is no evidence for this. 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 is often shown together with the two most-known early dinosaurs, Plateosaurus and Coelophysis, and sometimes shown as the latter's prey. Anachronism Stew and Misplaced Wildlife are in play here, since Coelophysis lived only in Late Triassic North America, while the plateosaur was around in Late Triassic Europe, but both dinosaurs did have relatives living alongside Heterodontosaurus in southern Early Jurassic Africa. Some suspect that the heterodontosaur could have defended itself well against enemies thanks to its robust tusks like modern baboons and peccaries do with big cats, but this is not demonstrable due to the lack of fossilized combat like the one between Protoceratops and Velociraptor.

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

Tiny Fore-Runners: Lesothosaurus & Fabrosaurus *

When talking about ornithischians, we can find the same issues as in saurischians: in the Triassic/Early Jurassic they were all so similar to each other that it’s hard task to classify them accurately. Nonetheless, they are extremely important animals for scientists, despite their often-tiny size. Other than the scelidosaurians and the heterodontosaurians (which make two distinct groups on their own), we have some other examples of early ornithschians, 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, but newer research suggests that it could in fact be a very basal, armorless thyreophoran, thus the ancestor of scelidosaurians, stegosaurians, and ankylosaurians. From Early Jurassic Southern Africa like Heterodontosaurus, its name derives from the Kingdom of Lesotho, a small South African nation (once called Basutoland) where its remains were dug out in 1978; the species name diagnosticus underlines its importance to understanding early ornithischian evolution. Fragmentary remains from Lesotho that have been named Fabrosaurus australis ("Southern Fabre's lizard") may be synonymous with it; even though they were named slightly before Lesothosaurus, in The '60s, Fabrosaurus would not be the valid genus name for this dinosaur, as its fossils are too dubious to be properly classified as a distinctive species (much like what happened with Troodon and Stenonychosaurus).

In old textbooks, the "fabrosaur" was often shown as the protypical 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 that have also been classified as "hypsilophodonts", like Nanosaurus.

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

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

About this dinosaur, there are the same issues as Heterodontosaurus and Scelidosaurus in pop-portrayals: it can be shown living alongside Triassic icons Plateosaurus and Coelophysis (often as prey for the latter), despite being from the Early Jurassic. Like Hypsilophodon, Heterodontosaurus, or the prosauropod Mussaurus, Lesothosaurus is also usually cited as an example of a particularly small herbivorous dinosaur.

1. Entry Time: undetermined
2. Trope Maker: Their status as the precursors of the other ornithischians

Little-Armored Critter: Scutellosaurus *

Scutellosaurus ("lizard with small shields", not to be confused with the Permian reptile Scutosaurus) has traditionally been considered the most primitive thyreophoran, variably classified in the Scelidosaurids or in its own family, Scutellosaurids.

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

Like the scelidosaur, Scutellosaurus lived in the Early Jurassic, but it was found not in Europe like the former but rather North America, living alongside the popular double-crested Dilophosaurus and the small early land-living crocodile relative Protosuchus. Some portrayals have shown the scutellosaur as the dilophosaur's prey, but this is not confirmed. Despite its small size for dinosaur standards Scutellosaurus was slightly bigger and heavier than Protosuchus, and the latter arguably hunted only young scutellosaurs. It is unknown if the dinosaur had the same feather-like structures seen in many small ornithischians, but if it had them, they would have been interspersed between the bony scutes that give to it its name.

1. Entry Time: undetermined
2. Trope Maker: its armor

Other hadrosaur predecessors

Sorry, these aren't here. If you're looking for Altirhinus, Mantellisaurus, Callovosaurus, Rhabdodon, Yandusaurus, Pisanosaurus, Technosaurus, Fruitadens, Eocursor, Tianyulong, Kulindadromeus, and others, see here. And here.

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