Chaoyangsaurus youngi

By Jack Wood

Etymology: Reptile from Chaoyang 

First Described By: Zhao, Cheng, & Xu; 1999 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Marginocephalia, Ceratopsia, Chaoyangsauridae  

Status: Extinct 

Time and Place: Sometime between 151 and 146 million years ago, in the Tithonian of the Late Jurassic 

Chaoyangsaurus is known from the Tuchengzi Formation of Liaoning, China 

Physical Description: Chaoyangsaurus was a small, bipedal herbivore – like so many other dinosaurs from the time – but differed from its close cousins in some important ways. Namely, it had a distinct top beak to go with the lower beak, that was slightly hooked; and in addition to that, it had a ridge on the back of its head. These two factors signal out the little guy for what it was – one of the earliest known Ceratopsians! This famed, iconic group of dinosaurs really got their start from such humble beginnings as Chaoyangsaurus. It would have had longer legs than arms, and run about bipedally – with a slightly larger head for the rest of its body. It may have been completely fluffy – like other small bipedal herbivores – or had distinctive quills on its tail, like it’s later relative Psittacosaurus. Either way, it would have had fluff in some form. Chaoyangsaurus was quite small, only about a meter long. 

Diet: As a small Ornithischian, Chaoyangsaurus would have primarily fed upon low-lying plants such as ferns. 

By Nobu Tamura, CC BY 3.0

Behavior: Chaoyangsaurus would have been a fairly skittish animal, running about in its environment attempting to avoid predators with speed rather than defense. Though that beak would have been good at snipping off tough vegetation, it wouldn’t have been the best in defense from larger predators. However, that ridge on the back of its skull may have provided extra defense for the head if something knocked into it. Chaoyangsaurus was probably at least a little social – since most small bipedal Ornithischians seemed to be so – using calls and notice from the other members of the flock to escape predators. The quills it may have had would have been good for display, so it could signal to each other that they were looking for mates and the like. It would have taken care of its young, which would have been even smaller! Too cute to process, really! 

Ecosystem: Chaoyangsaurus lived in the Tuchengzi Environment, a late Jurassic environment from far western China. In fact, it is a transitional environment between the famed Daohugou Biota – a showcase for small, fluffy animals of the Mid Jurassic – and the even more famed Jehol Biota – a showcase for the small, fluffy animals of the Early Cretaceous. This transitional environment was not as lush, not as well preserved, and extremely dry – seemingly, semi-arid. This dry environment lead to the extinction of the unique and beautiful Daohugou auna. It was also more poorly preserved at this time, though clearly dinosaurs and other life forms were around (as Chaoyangsaurus was). Chaoyangosaurus was probably primarily preyed upon by a mysterious Raptor, from which we only have footprints; there was also a small general theropod present, and the small pterosaur Orientognathus. This environment would eventually grow lush again – and with it, small fluffy creatures would explode into amazing abundance once more. 

By José Carlos Cortés

Other: Chaoyangsaurus shows the start animals like Triceratops and company really had – as these small, nippy bipedal creatures, running around in the undergrowth of the Jurassic and Early Cretaceous, trying to escape the larger predators! The quadrupedal stance, large frills, and horns would come much later – the giant horns, not until the Late Cretaceous. 

~ By Meig Dickson 

Sources Under the Cut 

Barosaurus lentus

By Ripley Cook

Etymology: Heavy Reptile 

First Described By: Marsh, 1890 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Sauropodomorpha, Bagualosauria, Plateosauria, Massopoda, Sauropodiformes, Anchisauria, Sauropoda, Gravisauria, Eusauropoda, Neosauropoda, Diplodocoidea, Diplodocimorpha, Flagellicaudata, Diplodocidae, Diplodocinae 

Status: Extinct 

Time and Place: Between 150 and 149 million years ago, in the Tithonian of the Late Jurassic 

Barosaurus is known from the Brush Basin Member of the Morrison Formation in South Dakota, Utah, and Wyoming. Potential specimens of Barosaurus are known from other locations of the Morrison Formation; the entire range of this habitat at the time of Barosaurus is shown below in green (with the range of Barosaurus inside of it, in blue).  

Physical Description: Barosaurus in a lot of ways is a fairly typical Diplodocid sauropod – long, large, and with a distinctive whip-tail. But, when you dig under the surface, Barosaurus has nothing truly “typical” about it. The neck of Barosaurus is next-level in its length – and the tail is ridiculous to match. In fact, the estimates of the length of Barosaurus get huge – it was probably more than twenty-six meters long, and some of the most upper estimates of Barosaurus have it at fifty meters long! This would make it one of, if not the, largest known dinosaurs – and certainly the longest! Though it does have a long tail, it differs in appearance from its cousin Diplodocus primarily by having a proportionally longer neck and shorter tail. It was also more slender than Apatosaurus, though it was longer than that contemporary. How did Barosaurus get such a long neck? It literally converted one of the back vertebrae into a neck vertebra! This is so fascinating that I can’t get over it – its close relatives, like Diplodocus, did not employ this to get a longer neck, indicating Barosaurus was using its long neck for things that its cousins were not. Barosaurus was also weird in not having as high of spines on its vertebrae as its cousin Diplodocus and other members of the group. In addition to all of that – it had shorter vertebrae in the tail, which made it shorter than in other members of this group! Interestingly, the bones on the underside of the tail were forked and had forward spikes, which would have given it similar strength to that of Diplodocus; it was probably still a whiptail like other members of this group, though not as much of one as its relatives. 

By Slate Weasel, in the Public Domain

Of course, the distinctiveness of Barosaurus is primarily limited to the length of the animal and its spine. In terms of limbs, it had fairly identical limbs to its cousin Diplodocus, though it did have fairly long forelimbs compared to its cousin (by… an almost imperceptible amount, however). Though the feet of Barosaurus aren’t known, it is reasonable to suppose that it would have had feet similar to Diplodocus – with only one claw on the front feet and three small claws on the hind feet. The skull of Barosaurus is not known, but it probably would have been long and low, with peg-like teeth in the front of the jaws for grazing on plants. Its neck was not very flexible in the vertical sense, but it was much more flexible in sweeping from side to side. It is possible that there were spikes of some sort at the end of the tail, which would have packed quite a punch when the tail was used to whip other animals. And, finally, it would have been entirely – if not almost entirely – scaly all over its body. It is also possible that Barosaurus may have featured some brilliant colors, especially in the tail, for communication with other members of the species. 

Diet: Barosaurus would have primarily fed on high-level vegetation, able to reach much of it at its natural neck height and then – on top of that – being able to rear up to 50 meters high via going on its hind legs. However, a lack of vertical reach in terms of neck flexibility means that it probably would have swept over a wide area for food, rather than going up and down in the tree level like other Diplodocids. This would have allowed Barosaurus to move very little – if at all – while eating, instead of moving over large distances in search of vegetation. 

By Scott Reid

Behavior: Barosaurus was not especially common in its environment, so the question of its social nature is actually somewhat important. Fossil evidence indicates at least some sociality in other Diplodocids – herding, or at least small herds, of other sauropods on the Morrison are clear from fossil evidence and trackways. The question remains – did Barosaurus do what its cousins did? The question is, of course, up in the air without more fossil evidence. It is possible that, in an environment with hundreds and hundreds of large sauropods to feed, Barosaurus may have been more solitary to aid in getting enough food without competing too much with one another. Alternatively, it may have also lived in social groups, allowing for the safety of weaker members of the herd and more cohesiveness in finding food. 

Barosaurus, like other Diplodocids, would have been able to rear up on its hind legs to get food. This action would have also made Barosaurus even taller than usual, which would have been fairly imposing to predators nearby. It had a whip-tail, which would have allowed Barosaurus to make very loud sonic cracks in the air; if that tail was covered with spikes, as in other members of the group, it would have also lacerated the skin of other dinosaurs. Still, even without spikes, it would have packed quite a punch for any predators that might have tried to attack it. The sounds of the tail would have been a warning; it is possible that such sounds would have been used in communication with one another, and potentially even display in competition for mates and food and similar things. The impossibly long neck probably was also a sort of sexual display structure, since the longer neck indicated being able to reach more food without walking around. It is uncertain whether or not it would have taken care of its young; while there is no evidence either way – which usually would lead to concluding it did, given the fact most living archosaurs do and there’s extensive evidence of such in extinct dinosaurs – other sauropods (aka the titanosaurs) probably didn’t. So, for now, the jury on that is out. 

By Fred Wierum, CC BY-SA 4.0

Ecosystem: Barosaurus lived in the Morrison Formation – an extensive, expansive semi-arid, seasonal floodplain that covered most of Western North America during the Jurassic and was filled with iconic dinosaurs and other animals that we usually think of when we think of the “Jurassic.” Though the Morrison was as arid and open as a modern savanna, the lack of extensive flowering plants at this time rendered the habitat more like a ridiculously huge scrubland. There were a variety of trees – conifers, ginkgos, cycads, and tree ferns – dispersed among the bushes and horsetails and other plants. They congregated around rivers, which were havens of life amongst the arid territory. At the time of the Brushy Basin Environment – the last part of the formation, where Barosaurus could be found – this environment was much muddier and wetter, potentially indicating a change in ecology that would lead to the end of the Morrison Formation, and an extinction of the animals there. There were also expansive volcanic explosions that lead to much of the preservation we see there. A large salt lake present would have been a major feature of the environment, and it was connected to extensive wetlands that formed a break in the wider scrubland around the habitat. 

By Danny Cicchetti, CC BY-SA 3.0

Barosaurus may be known from the entire Brushy Basin Environment of the Morrison; however, confirmed fossils of this dinosaur are only known from a few sites. So, in my map above, I give two colors – the wider green color to show the whole ecosystem, aka the wider area that Barosaurus may have ventured in to; and the smaller blue color to show the confirmed range of this dinosaur. In that confirmed range, Barosaurus lived alongside a lot of other animals – in fact, there’s a reason the Morrison is so iconic – its characteristic and distinctive fossils, both of dinosaurs and not of dinosaurs. Barosaurus has been found in, literally, the same sites as other animals – it is known to have lived alongside the predator Allosaurus; in another site, turtles and Pseudosuchians and the Choristodere Cteniogenys, as well as Allosaurus and the more bulky sauropod Camarasaurus; in yet another, Barosaurus lived alongside many turtles, the Pseudosuchians Hoplosuchus and Goniopholis, the tuatara-like Opisthias, and a wide variety of dinosaurs – other sauropods like Diplodocus Apatosaurus and Camarasaurus, predators like Allosaurus Torvosaurus and Ceratosaurus, and Ornithiscians like Stegosaurus Dryosaurus and Uteodon. So, Barosaurus was a part of a very wide and diverse community, with a great diversity in terms of herbivores and predators that would have attacked Barosaurus. That being said, there were many other animals that may have lived alongside Barosaurus, based on just… probability, even though they weren’t found directly with it. There were other stegosaurs like Alcovasaurus and Hesperosaurus; more small running herbivores like Nanosaurus; larger bulky bipedal herbivores like Camptosaurus; more sauropods, including Apatosaurus and Supersaurus; and smaller predators that would have probably been more of a threat to Barosaurus young than adults – Marshosaurus, Coelurus, Ornitholestes, and Stokesosaurus. Sadly, the organization of the Morrison is something of a mess – so, while many other dinosaurs and animals lived alongside Barosaurus, we can’t exactly be sure which ones. There were probably a variety of Multituberculate, Tinodontid, Eutriconodont, and Dryolestoid mammals, as well as others; some pterosaurs were probably there like Harpactognathus, and, of course, there were amphibians as well. This makes the Morrison one of the better examples of an environment to highlight as a representative of a particular time in Earth’s history – since it showcases so many different living things! 

By José Carlos Cortés

Other: Barosaurus was a close relative of Diplodocus, though it is difficult to determine how close, as the evolutionary relationships between the Diplodocids are still being worked out via phylogenetic studies. It is possible that an offshoot of Diplodocus (which were around before Barosaurus evolved) split to take advantage of not moving much to eat, and instead sweeping its neck around to gather food. For a while, another sauropod in Africa was considered to be a species of Barosaurus; today, however, it seems to be very clearly in its own genus, Tornieria, and actually far removed from both Diplodocus and Barosaurus (while still being in this closely related family group). So, for now, Barosaurus is only known from North America. These dinosaurs were distinctive long and slender sauropods, as opposed to their long and bulky cousins, the Apatosaurines, that they lived alongside. 

~ By Meig Dickson

Sources Under the Cut 

Turiasaurus riodevensis

By José Carlos Cortés

Etymology: Reptile from Turia 

First Described By: Royo Torres et al., 2006 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Sauropodomorpha, Bagualosauria, Plateosauria, Massopoda, Sauropodiformes, Anchisauria, Sauropoda, Gravisauria, Eusauropoda, Turiasauria 

Status: Extinct 

Time and Place: About 146 million years ago, in the Tithonian of the latest Jurassic 

Turiasaurus is known from the Villar del Arzobispo Formation of Aragón, Spain 

Physical Description: Turiasaurus was a huge, lumpy sort of sauropod, probably reaching between 36 and 39 meters in total length, and weighing up to 48 tonnes. This made it quite huge indeed, and Turiasaurus would have been an unmistakable figure on the European landscape – in fact, it is one of the largest European sauropods ever known. It had a fairly large but short skull, which was extensively distinctive – with a very round upper head and large holes in the skull to help keep it lightweight. The top of the skull sloped down to the tip of the snout, and then the lower jaw was more boxy, as was the back of the head. This lightweight skull was accompanied by small, triangular teeth, clustered very densely in the jaw. This skull was similar in a lot of ways to that of Camarasaurus, indicating that such a high skull is in fact ancestral to the group of more derived sauropods, the Neosauropods, and that things like Diplodocoids with their long, thin skulls, developed that condition independently. As for the rest of the body, it had somewhat longer front limbs than hind limbs, a short tail, and a long neck – in a lot of ways, convergent with the later-derived Macornarians like Camarasaurus and Brachiosaurus. This has always been fascinating to me, because another group of non-Neosauropods, the Mamenchisaurids, were convergent in a lot of ways with the Diplodocoids – indicating that Tall versus Long was a constant ecological battle in sauropods, and in Turiasaurus, Tall won out! Turiasaurus was so huge it was probably entirely scaly; any feathers left would have only been for display, and even that seems unlikely. 

By Matt Martyniuk, CC BY-SA 4.0

Diet: Turiasaurus would have been a high-level browser, able to reach foliage up to six meters tall. It would have then browsed generally on whatever plant material it could get too! 

Behavior: Turiasaurus would have had to have spent most of its time foraging on the treetops, getting as much food into its very large belly as possible. When not foraging, it would have been on the move, searching for more food! It seems likely that Turaisaurus would have associated with other members of the genus, in order to stay safe – though huge, they weren’t very fast, so numbers would have been useful if nothing else, especially for younger and smaller and unhealthy and old members of the group. It is uncertain how complicated its behavior would have been, or if it took care of its young, though there isn’t evidence that it did not – and young-care is the normal state for Archosaurs. 

By Levi Bernardo, CC BY-SA 4.0

Ecosystem: The Villar del Arzobispo Formation was a transitional environment, literally recording the time period when the Jurassic turned into the Cretaceous. This was a coastal floodplain environment, with a variety of muddy and sandy areas, and it was frequently affected by flooding events that would lead to rapid burial of the animals present. There were a wide variety of marine animals here, indicating that Turiasaurus and its neighbors were foraging on the tree line along the coast. This formation was lousy with sauropods and stegosaurs – in addition to Turiasaurus there were the sauropods Losillasaurus and Aragosaurus, the stegosaur Dacentrurus which was very common in the area. There were also large Allosaurid predators, and smaller fluffy Coelurosaurs, though these haven’t been named; in addition, there were turtles and crocodylomorphs present in the area. 

Other: Turiasaurus is a fascinating dinosaur mainly because of its evolutionary implications. For a long time, the prevailing opinion about the long-necked (sauropod) dinosaurs was that the Diplodocoids and Macronarians – things like Apatosaurus and Brachiosaurus and the infinite forms of Titanosaurs – essentially replaced earlier forms of Sauropods all over the globe except for maybe East Asia. However, fossils like Turiasaurus show that these earlier derived sauropods (non-Neosauropods) were not only still around by the end of the Jurassic, but successful into the Cretaceous. Turiasaurus and its relatives were found around all over the Northern Hemisphere well into the Cretaceous period, and were clearly able to carve out their own niche alongside other sauropods. 

~ By Meig Dickson

Sources under the Cut 

Tuojiangosaurus multispinus

By Scott Reid

Etymology: Reptile from the Tuo River

First Described By: Dong et al., 1977

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasaria, Thyreophora, Thyreophoroidea, Eurypoda, Stegosauria, Stegosauridae

Status: Extinct

Time and Place: Between 160 and 158 million years ago, in the Oxfordian of the Late Jurassic 

Tuojiangosaurus is known from the Upper Shaximiao member of the Dashanpu Formation of Sichuan, China 

Physical Description: Tuojiangosaurus was a medium sized stegosaur, ranging about 7 meters long and 2 meters tall, featuring a long neck, small head, and armor along its back. Like other stegosaurs, it was also quadrupedal, with a long flexible tail. Like other members of its group, this dinosaur had plates along its back and spikes on its tail (called a Thagomizer) as its armor. Tuojiangosaurus was especially distinctive from other stegosaurs because it’s plates were somewhat small and excessively sharp and triangular. These plates were smaller towards the head and end of tail, and grew bigger until reaching a peak in the middle of its back. 

by Slate Weasel, in the Public Domain

It had a fairly typical series of spikes on the end of its tail, though, and it may have had long sharp spines on its shoulders for display. It had fairly long legs, which would have given it decent mobility as far as bulky quadrupeds go – and a tiny head with a little beak in the front. It probably wouldn’t have had any feathers, given it was several tonnes in weight, but some may have remained just for lack of need to lose them (like hair on elephants) or for extra display. Still, it would have probably been primarily scaly. The plates would have probably been able to flush with color for display. 

Diet: Tuojiangosaurus would have primarily fed on medium-level vegetation, using its narrow head and tiny beak to snip off particular bits of plant that it wanted to eat (and avoiding those that didn’t), making it a specialist browser. 

By Paleocolour, CC BY-SA 4.0

Behavior: Tuojiangosaurus would have spent a good portion of its day eating, browsing on lower level vegetation while wandering through the foliage. It may have been able to lean up on its hind legs to reach higher vegetation, but because it had a flexible tail it seems unlikely that it was able to use it as a sort of “third leg”. Its long legs would have allowed it to banter away at a fairly quick trot when needed, but it certainly wasn’t lacking in the defensive structures when it needed to defend itself from large predators in the area. The thagomizer on its tail would have been an excellent source of defense, and there is fossil evidence of holes in the bodies of predatory dinosaurs that match with thagomizer patterns. By whipping its flexible tail at an enemy,Tuojiangosaurus would have been well-equipped for defense. 

Tuojiangosaurus was a creature of extensive display, using its beautiful plates and spikes to show off for other members of the herd. The plates could be flushed with blood and color, both to make the dinosaur look bigger and to help communicate with others. The long shoulder spikes would have been indicative of the fitness of an individual, as they wouldn’t have been very useful for anything else. With so many display structures, it stands to reason that Tuojiangosaurus would have been an active and social animal, communicating regularly with herd members (and probably also using sound to do so – almost all close living relatives of Tuojiangosaurus are loud, it stands to reason that Tuojiangosaurus would be too). These dinosaurs probably would have taken care of their young, though it’s hard to tell for how long. It’s possible that some contemporary stegosaurs are actually juveniles of Tuojiangosaurus. 

By Abelov2014, CC BY-SA 3.0

Ecosystem: The Upper Shaximiao environment was a wide, semi-arid floodplain, with periodically devastating floods that lead to extensive mud forming in the region, in between seasons of more sandy terrain. Rivers were present throughout the region, feeding into a large lake, along with horsetails, conifers, and ginkgoes – making it a fairly lush forest area, with periodic periods of hardship. 

This was a very diverse ecosystem, as far as animals were concerned – there were synapsids like Bienotheroides and Shunotherium; many kinds of turtles; pseudosuchians like Sichuanosuchus, Peipehsuchus, and Hsisosuchus; and dozens and dozens of dinosaurs – this environment and its lower equivalent are often called the Morrison of East Asia. Tuojiangosaurus was accompanied by many other stegosaurs like Gigantpinosaurus, Chunkingosaurus, Chialingosaurus, and Yingshanosaurus – making this one of the most diverse ecosystems when it comes to stegosaurs. There were smaller, bipedal, fast and fluffy ornithischians as well, like Yandusaurus and Gongbusaurus. Giant sauropods were fixtures in this enviornment – dozens and dozens of varieties of Mamenchisaurus were present, as well as some Omeisaurus. There was also the brachiosaur-relative Daanosaurus. Small meat-eating dinosaurs were present, like Sinocoelurus, but also larger predators like Szechuanosaurus and the more famous Yangchuanosaurus, which would have been major threats to the livelihood of Tuojiangosaurus. In short – a flourishing Jurassic ecosystem. 

By José Carlos Cortés

Other: Tuojiangosaurus is a fairly derived Stegosaurian dinosaur, just outside the group including such iconic dinosaurs as Stegosaurus. It is also, arguably, the third most famous member of the group, though when you get down to it Stegosauria has way too many iconic members for how small of a group it is. 

~ By Meig Dickson

Sources under the Cut 

Caihong juji

By José Carlos Cortés

Etymology: Rainbow

First Described By: Hu et al., 2018

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoromorpha, Maniraptoriformes, Maniraptora, Pennaraptora, Paraves, Eumaniraptora, Avialae, Anchiornithidae 

Status: Extinct

Time and Place: 161 to 160 million years ago, in the Oxfordian of the Late Jurassic 

Caihong is known from the Tiaojishan Formation of Liaoning, China 

Physical Description: Caihong was a small dinosaur, only reaching 0.4 meters in length, and weighing only a little more than a single pound. It was weird in a lot of ways when you got down to it – it is a rare example of a Paravian (birds and their closest relatives) with a bony crest on its snout, which was small and triangular shaped like most almost-birds at that time. In fact, beyond the bony crest, it had a head very similar to that of Archaeopteryx. The crests were long and bony, pointed sideways and curving upwards. It had tightly packed, slender teeth in the front of the jaws, which space out more towards the back – and in the middle they tend to curve the most. It had a short neck and a normal-sized torso, but weirdly enough Caihong had a fairly short tail for a dinosaur of its type. It had fairly short arms compared to other dinosaurs in its group (the Anchiornithids), indicating that any flight or gliding ability could have been poorer than usual – but it did have longer lower arms than upper arms, and longer wing feathers, indicating decent flight capabilities. Caihong also had very long fingers. Its hips were rather rectangular in shape, weirdly enough, unlike other paravians which usually had triangular-shaped hips. Caihong also had very long legs, with somewhat short toes and noticeable sickle claws (like other paravians). 

By Tom Parker, CC BY-SA 4.0

Caihong is, of course, most notable for its coloration. Like other Anchiornithids, it was excessively fluffy. Fossils of Caihong include remains of the original plumage – not just impressions – which showcase the extreme density of the feathers. In fact, it’s a tad difficult to identify each individual one. These feathers were extremely long (though some were shorter and wavier than others) making them distinct from other dinosaurs – in fact, it had some of the longest feathers known in its group. These feathers preserve distinct coloration, which show that most of the body of Caihong were black and iridescent, like many living birds such as crows and ravens. More notably, coloration in the neck and head showcase iridescence like modern hummingbirds and trumpeters – giving Caihong a distinctive rainbow neck. In fact, it is the first Mesozoic Dinosaur found with such structures – called plate-like melanosomes – making it one of the gayest of non-avian Dinosaurs. Happy Pride Y’all. 

By Ripley Cook

Diet: Like other Anchiornithids, Caihong probably fed mainly on small animals and insects, which were extremely common in its environment. 

Behavior: Like other Anchiornithids and Paravians in general, Caihong showcased a mixture of behavior indicating its intermediate position on the bird evolutionary tree – it could probably fly at least a little bit, but mainly used its wings for other behaviors that were in many ways flight-adjacent. Able to fly from tree to tree and place to place in its forested environment, it also would have engaged in Wing-Assisted-Inclined-Running, or WAIR. In WAIR, Caihong would flap its wings fast enough to jump onto a steep or vertical surface and run up it – using the lift generated by its wings to gain height. It could have balanced on top of prey with its claws, and flapped its wings to stay balanced, a behavior known as Raptor-Prey-Restraint, or RPR. However, given it mainly ate small food, it would have more often just trapped the food with its foot claw, and held it down with its (light) weight. It was a small birdie thing running about between the trees, and probably used its sparkling feathers on its neck and tail fan and wings more often for sexual display. 

By Anthony F.

Given it was an active, warm-blooded animal, Caihong most likely took care of its young. Whether or not it lived in family groups, larger flocks, or mainly on their own is more of a question – they don’t seem to have been quite as common as their cousin Anchiornis. Overall, it was an agile and active small predator, and a very flashy one at that. 

By Scott Reid

Ecosystem: The Tiaojishan environment was a temperate rainforest, dominated by giant conifer and ginkgo trees, as well as horsetails, cycads, ferns, and clubmosses. Nestled in a valley with extensive lakes, rivers, and volcanic activity, it was an extremely lush environment – and didn’t experience the winters of the later Jehol biota. It probably had clear wet and dry seasons. This was an environment of fluffy creatures and flighted creatures. Here there were a variety of salamanders, lizards, and invertebrates. There were also very unique mammals and almost-mammals – Agilodocodon, a tree-climbing squirrel-like creature; Arboroharamiya, a rodent-like critter with a prehensile tail; Castorocauda, a beaver-like non-mammalian synapsid; Docofossor, a burrowing almost-mammal similar to the Golden Mole; Juramaia, a shrew-like stem-placental mammal; Megaconus, a hyrax-like creature; and Volaticotherium, a gliding colugo-like creature adapted to eat insects. 

Tiaojishan Environment by Julio Lacerda, used with permission from Pteros

This was also a land of pterosaurs – so many pterosaurs. There were long-tailed, crested, big-headed forms like Archaeoistiodactylus, Changchengopterus, Darwinopterus, Kunpengopterus, Pterorhynchus, and Wukongopterus. There were smaller-headed long-tailed piscivorous forms like Fenghuangopterus, Jianchangnathus, Jianchangopterus, and Qinglongopterus. And then there were the particularly fuzzy, blunt-snouted, big-eyed anurognathids Jeholopterus and Dendrorhynchoies. This cacophony of creatures showcased a transitional period in pterosaur evolution – with many of the more iconic Jurassic kinds living alongside the precursors to the giant Cretaceous pterosaurs we all know and love.

By Lucas Attwell, CC By-SA 4.0

As for Dinosaurs, there was diversity abundant too. Caihong lived with many of its closest relatives: Anchiornis, Auornis, Eosinopteryx, Pedopenna, Xiaotingia, and Serikornis – all extremely fluffy, like Caihong, and coming in a wide variety of colors and sizes. This was the paradise of the Anchiornithids, showcasing a truly amazing diversity. They weren’t the only birdie dinosaurs, however – Yi, Scansoriopteryx, and Epidexipteryx flew (badly) from tree to tree, the weird dragons that they were. And, of course, there was one of the most notable fluffy Ornithischians – Tianyulong, the Heterodontosaurid, just to show how Ornithischians were a thing in the Tiaojishan, too. 

By Ashley Patch

Other: The Anchiornithids have always been a very confusing group of dinosaurs, because they straddled the line between things commonly called birds (Archaeopteryx et al.,), and things that have always been kept outside of that grouping (Troodon et al.). And, as recent phylogenetic analyses have shown, this is an accurate description of their placement. The Anchiornithids – like Caihong – are literally in-between Archaeopteryx and Troodon, making them the Most Transitional Birdie Dinosaurs of all. Are they birds? Are they not birds? I tend to go with the line of thinking that most dinosaurs are birds, but for the sake of argument – they certainly blur the line. As more Anchiornithids are found and studied, even more will probably come to light about the evolution of dinosaurs towards more birdie traits throughout the Jurassic and then Cretaceous periods. 

~ By Meig Dickson, edited by Henry Thomas

Sources under the Cut

Xingxiulong chengi

By Ripley Cook

Etymology: Dragon from the Xingxiu Bridge

First Described By: Wang et al., 2017

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Sauropodomorpha, Bagualosauria, Plateosauria, Massopoda, Sauropodiformes

Status: Extinct

Time and Place: Between 201.3 and 199.3 million years ago, in the Hettangian of the Early Jurassic 

Xingxiulong is known from the Shawan Member of the Lufeng Formation 

Physical Description: Xingxiulong was a medium-sized prosauropod, about four to five meters long with a height of one to one and a half meters at the hip. It had a smooth jaw, unlike other prosauropods of the time and place, and it had a long jaw like Lufengosaurus. It’s skull was somewhat short, much like that of the later Camarasaurus, and it would have relied more on its neck and hands to grab food rather than a longer snout. This broad snout would have also made it a generalist, rather than specialist, browser. It’s neck was fairly long and muscular, like in other Sauropodomorphs; it also had a long tail.

Xingxiulong was a fairly bulky and heavyset prosauropod, indicating the journey of this line of dinosaurs as it evolved into Sauropods (though of course, Sauropods were already around at this point in dinosaurian evolution). It even had more vertebrae at the hip, like sauropods, and unlike other prosauropods of its time and place. It also had a longer hip bone than prosauropods – once again, one more like the later sauropods. It’s legs were also very robust, like those of the sauropods. Xingxiulong had a very large gut, allowing it to store more food while digesting. This probably is correlated with its increased ability to hold up a large body weight, compared to its contemporaries. In short, Xingxiulong is a prime example of the slow, step-wise evolution of the prosauropods towards the large nature of the Sauropods – though, ,of course, Xingxiulong is just an offshoot of that line.

Being somewhat larger, Xingxiulong probably was more scaly than not, though it still may have possessed feathers. It probably would have stille mostly walked on just its hindlimbs, though it may have been able to walk on its forelimbs when need be. It still would have mainly used its forelimbs in feeding, more than in locomotion. 

By José Carlos Cortés

Diet: Xingxiulong would have been a mid-level browser, feeding on a variety of fairly dry vegetation by reaching up with its arms and long neck.

Behavior: Xingxiulong, unfortunately, doesn’t have a very well-known behavior, though it probably would have spent most of its time browsing in its environment. It would have had to walk around its environment carefully, given how bulky it was and its large mass; it probably wouldn’t have been the fastest of dinosaurs. As a prosauropod, it most likely was active in its metabolism, and it probably took care of its young. It’s also entirely likely that Xingxiulong would forage in its environment in mixed-species herds, with all the other prosauropods of the time and place in which it lived.

Ecosystem: Xingxiulong lived in the Shawan environment of the Lufeng Formation, one of a few classic environments showing off the initial explosion of dinosaur evolution after the end-Triassic extinction. This was a lush environment, with many lakes, rivers, and overbanks. As such, it would have been a very lush and green environment, though no plant fossils have been reported. Here there were many other kinds of animals, especially transitional dinosaurs. In many ways, it was a counterpart to the South African Elliot Formation, in what it shows about the early evolution of large dinosaurs – though the Elliot was much more arid than the Lufeng.  

By Scott Reid

Contemporary with Xingxiulong, there were many other Prosauropods that probably would have all grazed together in the plant line in mixed-species herds. Here, there was Jingshanosaurus, Yunnanosaurus, Lufengosaurus, and Gyposaurus, all in the specific environment from which Xingxiulong is known. There was also theropods like the smaller Panguraptor, and the large Sinosaurus which would have been a major pain for Xingxiulong. The potential Coelurosaur Eshanosaurus was present too, but this is doubtful and honestly it probably was just another prosauropod. Also present was Lukousaurus, which more likely than not is just a crocodilian. No ornithischians are known from the same environment as Xingxiulong, unfortunately.

Other: Xingxiulong, though very sauropod-like, was actually only midway on the sauropod family tree! Many animals, even in its own environment, were just as close to sauropods as Xingxiulong was. Still, Xingxiulong gives us a decent picture of how sauropods evolved at the Triassic-Jurassic transition.

~ By Meig Dickson

Sources under the Cut 

Amygdalodon patagonicus

By José Carlos Cortés

Etymology: Almond Tooth

First Described By: Cabrera, 1947

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Sauropodomorpha, Bagualosauria, Plateosauria, Massopoda, Sauropodiformes, Anchisauria, Sauropoda

Status: Extinct

Time and Place: Between 180 and 175 million years ago, in the Toarcian of the Early Jurassic 

Amygdalodon is known from the Cerro Carnerero Formation of Chubut, Argentina 

Physical Description: Amygdalodon is a fairly poorly known early Sauropod, known really only from bone fragments and teeth. As an early sauropod, though, it would have been somewhat bulky, and probably somewhere around 12 meters long. It would have walked around on all fours, and very similar to other early branching sauropods. It would have had a semi long neck and long tail, but no extreme specializations either way. It would have probably been entirely scaly due to its large body size.

Diet: Amygdalodon would have been primarily herbivorous.

Behavior: It is uncertain what the behavior of Amygdalodon would have been, given we don’t have a lot of fossil evidence of this dinosaur. That being said, it probably spent most of its day feeding, and most likely lived in large groups of other Amygdalodon for protection. It probably also took care of its young, and had an active metabolism – but, again, this is just conjecture. 

By Ripley Cook

Ecosystem: Amygdalodon is known from a coastal environment, a pebbly beach associated with sand as the pebbles were eroded from the waves of the sea; Amygdalodon itself mainly keeping to the rivers as they emptied out into the ocean. Unfortunately, no other dinosaurs were found alongside Amygdalodon; only one poorly preserved shrimp. So it is uncertain what sorts of plants Amygdalodon lived alongside, what other animals it interacted with, and what may have preyed upon it.

Other: Amygdalodon is the most basal known sauropod from the continent of South America!

~ By Meig Dickson

Sources under the Cut 

Lourinhanosaurus antunesi

By Ripley Cook

Etymology: Reptile from Lourinhã

First Described By: Mateus, 1998

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides

Status: Extinct

Time and Place: Between 153 and 150 million years ago, in the Kimmeridgian to Tithonian ages of the Late Jurassic 

Lourinhanosaurus is known from the Sobral and Amoreira-Porto Novo Members of the Lourinhã Formation of Portugal 

Physical Description: Lourinhanosaurus is a mysterious theropod – the bipedal predatory dinosaurs that evolved into such creatures as Tyrannosaurus and Allosaurus, and also birds! Lourinhanosaurus is mainly known from a partial skeleton, as well as many eggs and embryos! Despite this, we cannot figure out what type of theropod it definitely is. This was a fairly large dinosaur, at about 4.5 meters in length when reaching 17 years of age. It had long arms and legs, and a fairly large, bulky head. In short, it was a large predatory dinosaur – but so generic of one that we can’t pinpoint what kind!

As a moderately sized theropod, it’s very likely that it was covered in a coat of protofeathers; however, this cannot be exactly confirmed.

Diet: Lourinhanosaurus primarily fed on meat, especially larger herbivores.

Behavior: Lourinhanosaurus is known to have taken care of its young, which were found in nests with hundreds of eggs, indicating that multiple Lourinhanosaurus would all share the same nesting site. This kind of colonial nesting is fascinating, to say the least, as it’s not very common in theropods. This cooperative breeding may indicate that these were very social dinosaurs, living in large family groups and possibly hunting in these family groups.

In addition to that, Lourinhanosaurus was found with gastroliths – rocks in the stomach that helped to grind up food to make it easily digestible. Though many theropods have since been found with gastroliths, Lourinhanosaurus was the first! This means that it used these stones to help break apart the variety of meat that it would eat. 

By Audrey Horn, CC BY-SA 4.0

Ecosystem: Lourinhanosaurus is from the Lourinhã Formation, a Late Jurassic environment eerily similar to the Morrison, but from across the burgeoning Atlantic Ocean! This was a large, semi-arid floodplain environment, dominated by cycads and coniferswhere numerous herds of sauropods would roam. Here, Lourinhanosaurus lived alongside other predatory dinosaurs such as Allosaurus, Ceratosaurus, Richardoestesia, and Torvosaurus, which would have been major competitors – if not predators – of Lourinhanosaurus. Sauropods included such dinosaurs as Lourinhasaurus, Lusotitan, Supersaurus, and Zby, though only the juveniles would have probably been viable food for Lourinhanosaurus. Ornithischians included the small runners Trimucrodon and Alocodon, which would have been excellent Lourinhanosaurus food; the armored dinosaurs Dracopelta, Dacentrurus, and Miragaia; and the ornithopods Draconyx, Dryosaurus, Eousdryosaurus, and Phyllodon. There were also mammals such as Docodonts and Dryolestoids.  

Other: Lourinhanosaurus has been found to be a Carnosaur – so related to things like Allosaurus – or a Megalosaur – related to things like Megalosaurus – or a Coelurosaur – related to things like Tyrannosaurus. Maybe, one day, we’ll have an answer, but for now it’s still a Question!

~ By Meig Dickson

Sources under the Cut 

Yi qi

By José Carlos Cortés

Etymology: Strange Wing

First Described By: Xu et al., 2015

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoromorpha, Maniraptoriformes, Maniraptora, Pennaraptora, Scansoriopterygidae

Status: Extinct

Time and Place: Between 161 and 160 million years ago, in the Oxfordian age of the Late Jurassic 

Yi is known from the Tiaojishan Formation of Liaoning, China 

Physical Description: Yi was a small proto-bird, distinctive for its truly weird appearance. Weighing about 280 grams, with a wingspan of about 60 centimeters. It had a short, blunt skull, with a very rounded front of its mouth. The front teeth were angled forward out of the mouth, giving it a slightly bucktoothed appearance. It had a fairly short and squat body. It also had a very short tail, practically not present in terms of bone structure. Its forelimbs were long and slender, with long fingers extending from the hands. Its hindlimbs are not as well known, but they were somewhat short compared to the arms. 

By Matt Martyniuk, CC BY-SA 4.0

Yi is most notable, however, for its integument. It was heavily covered in feathers, but fairly simplistic ones, long and quill like. It did not have the complex, branching filaments common to the Pennaraptoran group. These quill feathers were also fairly stiff, rather than soft and flexible. Yi was covered in a very dense coat of feathers all over its body, with the densest grouping over its body. The feet and legs were also covered in feathers. At the end of the tail there were probably long, ribbon like feathers, though those are better known from its relatives. The weirdest part of the integument, though, was the membrane extending between the fingers, covered a little by the feathers on the arms but mostly bare. This membrane was almost like that of a modern-day bat. It also connected to the styliform, a rod of cartilage grown on the wrist to help support the membrane. Yi was preserved with some color – it was mostly black all over its body, with some yellow-brown patches on the head.

By Emily Willoughby, CC BY-SA 4.0

Diet: The diet of Yi is at least a little uncertain, though it seems likely it was an insectivore – possibly an omnivorous opportunist.

Behavior: So – could Yi fly?

Answer uncertain.

Of course I’m not going to leave it at that. But the problem is is that these wings are unique amongst dinosaurs and are, thus, hard to really compare in terms of physiology – especially since bird wings are nothing like this. Yi has been modeled in two ways – one in which the animal put together its wings like a bat (or a pterosaur) in terms of where the styliform bone was; and another in which it was more like a maniraptor; and finally a third like flying frogs. An analysis of these modes revealed that, if it was like a maniraptor, it would have had a loading capacity similar to ducks – which have larger wingspans than Yi did, indicating Yi could not fly in this model. The bat model was similar to shore birds, but this wingspan is very large and the aspect ratio is higher – again, higher than Yi. The frog model wasn’t tested. So what’s the conclusion?

Yi probably couldn’t fly.

Could it glide?

By Rebecca Groom

Maybe. 

Its center of mass was behind the control of the lift surface, which would have made it very unstable during flight. However, this was offset by a short fleshy tail and long feathers as in relatives – and it might have been able to flap a little to aid in movement, like the living Kakapo.

Either way, it’s likely that Yi spent a lot of time in the trees, climbing up and down branches and trunks in order to get food. It might have used those weird wings and tail in sexual display as well. Without more fossils, the rest is left up to speculation. 

Line art by Diane Remic; coloring by the author

Ecosystem: Yi lived in the iconic Tiaojishan Formation, a late Jurassic ecosystem preserving many transitionaldinosaurs between Bird and Not-Bird, showcasing how weird and wacky almost-birds got. The Tiaojishan was a subtropical to temperate, humid coniferous forest, not unlike northern California today. It was filled with ginkgoes, conifers, cycads, horsetails, and ferns, and was extremely densely forested and lush. This, plus volcanoes nearby, lead to a very productive and diverse ecosystem. Flight was the rule of thumb for the environment, too, with so many animals in the area adapted for gliding or powered flight. Here we know not only dinosaurs, but mammals, amphibians, pterosaurs, other reptiles, fish, and invertebrates a plenty. 

By Sam Stanton

When it comes to dinosaurs, almost all of them were Pennaraptorans – the kind that are especially birdie. There was Anchiornis, Auornis, Caihong, Eosinopteryx, Pedopenna, Serikornis, and Xiaotingia, a group of very early Avialans called the Anchiornithids – they were roughly at the same level of birdiness as Archaeopteryx, but looked very troodontid-y. Then there were the other Scansoriopterygids other than Yi – Epidexipteryx and Scansoriopteryx. Finally, there was the very fluffy heterodontosaurid, the maximum overpoof, Tianyulong. 

As for the cousins of the dinosaurs, the pterosaurs, there was extreme diversity as well – the weird Darwinopterans like Wukongopterus, Darwinopterus, Kunpengopterus, and Pterorhynchus; Ramphorhynchids like Fenghuangopterus, Qinglongopterux, Jianchangopterus, and Jianchangnathus; Anurognathids like Jeholopterus, and Dendrorhynchoides; an Istiodactylid Archaeoistiodactylus; and miscellaneous kinds like Daohugoupterus and Changchengopterus. All of these showcase the evolution of pterosaurs from Jurassic forms to the largers, shorter-tailed Cretaceous types! As for other reptiles, there were two unnamed lizards that had weird body proportions. 

By Ripley Cook

Amphibians are represented by many types of salamander – Pangerpeton, Liaoxitriton, Jeholotriton, Chunerpeton, and Beiyanerpeton. Mammals in this environment were fascinating too – one of the earliest tree-climbing mammaliaforms, Agilodocodon; a prehensile-tailed mammal Arboroharamiya; the semiaquatic stem-mammal Castorocauda; the burrower Docofossor; an extremely early placental relative Juramaia; the armadillo-mimic Megaconus; the rat-like Rugosodon; and the gliding Volaticotherium. There were many arthropods too, from flies to spiders to beetles to mayflies, as well as ostracods and bivalves.

Other: The phylogenetic position of Yi – and other Scansoriopterygids – is a bit of a mystery, with people arguing over whether or not they are Avialans like Archaeopteryx; basal to the group of Raptors + Avialans; or Oviraptorosaurs (Chickenparrots). Hopefully one day the mystery will be solved!

~ By Meig Dickson

Sources under the Cut 

Ornitholestes hermanni

By José Carlos Cortés

Etymology: Bird Robber

First Described By: Osborn, 1903

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Saurischia, Eusaurischia, Theropoda, Neotheropoda, Averostra, Tetanurae, Orionides, Avetheropoda, Coelurosauria, Tyrannoraptora, Maniraptoromorpha

Status: Extinct

Time and Place: Between 154 and 147 million years ago, from the Kimmeridgian to the Tithonian ages of the Late Jurassic 

Ornitholestes is known from the Brushy Basin and Lake Como members of the Morrison Formation in Colorado and Wyoming 

Physical Description: Ornitholestes was a small, bipedal carnivore, a coelurosaur – so the kind of dinosaur that would evolve into birds, raptors, and many more. Of course, raptors and proto-birds already existed by the time Ornitholestes did, so Ornitholestes was not their ancestor – but it sure looked a lot like it. Still, at first glance, Ornitholestes wouldn’t have looked much different from your average, run-of-the-mill small theropod like we’d see previously in the history of life. It was small, it had a long tail and long arms, a long head, and a short neck. It was covered in simple protofeathers, very little of which was doing anything different from protofeathers seen before. However, looking closer, more could be seen on this little dinosaur.

As a Maniraptoromorph – very close to when dinosaurs began to get really birdlike – Ornitholestes would have begun to show some of the initial characteristics of birds. It’s possible that it may have had the beginnings of elongated feathers on its arms – the start of wings. This is supported by the fact that it had long forelimbs – giving it ample surface to display feathers to members of the group. It also had fairly short hind legs – making it rather slow, slower than most previous theropods. It’s even possible it may have been more of a kicker than a runner, using its toe claws in defense and attack – and there are hypotheses that it may have had a sickle claw like later raptors and early birds did.

Early portrayals of Ornitholestes maintained that it had a crest on its nose, given a raised bone in the front of the snout. However, this has not been well preserved and thus remains a hypothesis more than a fact. Most consider the presence of the crest or horn to be rather unlikely. Still, it would have been a fairly fancy looking dinosaur, and one – between its long arms, and shorter legs – that showed what was to come in dinosaur evolution.

Diet: Ornitholestes was probably mainly carnivorous, given its teeth being serrated and sharp. Still, the ancestor of Coelurosaurs was probably omnivorous, making it possible that Ornitholestes may have supplemented its diet with plant material from time to time.  

By Fraizer

Behavior: Ornitholestes probably would have been more of a hopping predator, walking slowly through the floodplains and forests to track prey and jumping to catch it with its large grasping hands. The hands of Ornitholestes were able to extend together and then bend in together to grasp food, allowing it to hold prey in both hands – a trait that isn’t actually present in earlier theropods, at least, not to the same extent. The tail would have helped it to stay in balance while hunting. It probably would then hold the food and eat it, and thus stuck to smaller prey such as lizards, mammals, and baby dinosaurs. Since it had a short neck, it’s unlikely that it would have used its head much to grab food – its arms were unencumbered with large wings, and thus, it wouldn’t have had to avoid using them.

Given that Ornitholestes is fairly rare to find in the Morrison Formation – a geologic system famous for having way too many dinosaur fossils – it seems unlikely that Ornitholestes was particularly social, as it would theoretically be found in groups if it was. Instead, it was probably a loner, spending most of its time on its own and hunting for food. Given that, as a dinosaur, it probably still took care of its young – its possible that solitary Ornitholestes mothers would just raise their young until they were old enough to fend for themselves, or the father would like in modern ratites. Either way, the social groups seen in later birdie dinosaurs like the Ornithomimosaurs and Raptors (much less birds) probably wasn’t seen in Ornitholestes.

Ecosystem: Ornitholestes is from the Morrison Formation, one of the two most famous ecosystems with non-avian dinosaurs (the other being the Late Cretaceous Hell Creek formation). It was famous for its iconic animals – mostly sauropods, but also dinosaurs such as Stegosaurus and Allosaurus – that have become the stereotypical Jurassic picture of dinosaurs. This environment was a very large, semi-arid plain surrounding a system of rivers, which would dry up seasonally and flood afterwards, creating very muddy environments. There was also a giant salt lake – called Lake T’oo’dishi’ – and volcanoes that would cover the plain in ash. There were plenty of ginkgo trees, as well as cycads, conifers, ferns, horsetails, cycadeoids, and tree ferns. Forests would pepper the plains, which would have been dominated with ferns and other low growing plants, as grass wasn’t around yet.

It is nearly impossible to list all the animals we know lived in the Morrison – and plenty of them probably weren’t concurrent with Ornitholestes. Between that and the fact that the individual subunits of the Morrison are not really well diagrammed, I’m going to give us all my best guesses – important things found in roughly the same locations as Ornitholestes. 

By Scott Reid

The Brushy Basin Member of Colorado and Wyoming was by far the more diverse and better studied of the two where Ornitholestes has been found. There were other Coelurosaurs like Coelurus itself, as well as the early tyrannosaur Stokesosaurus, both of which being very similar in external appearance to Ornitholestes. There were also larger theropods like Allosaurus, Torvosaurus, Marshosaurus, and Ceratosaurus, which would have been real and present dangers to Ornitholestes. There were, of course, the iconic sauropods of the Morrison – Brachiosaurus and Camarasaurus; Supersaurus, Barosaurus, and Diplodocus; and, of course, Apatosaurus and Brontosaurus. Ornitholestes probably would have fed on babies from these dinosaurs, as well as eggs, which would have been small enough to be sources of food. There were Ornithischians as well – the smaller Dryosaurus, Nanosaurus, and Fruitadens probably would have made good food for Ornitholestes; whereas the larger ornithopod Camptosaurus would have been a big no-no. Extreme dangerous would have come from the armored dinosaurs Stegosaurus, Hesperosaurus, Alcovasaurus, and Mymoorapelta.

There were, of course, many non-dinosaurs in the Brushy Basin member as well, which would have probably made up more of Ornitholestes’ diet than dinosaurs would have – just, you know, size-wise. There were pterosaurs like Mesadactylus, Kepodactylus, and Harpactognathus; stem-crocodiles of all shapes and sizes like Amphicotylus, Diplosaurus, Eutretauranosuchus, Fruitachampsa, Hallopus, and Maceloganthus; and turtles like Dinochelys, Dorsetochelys, and Glyptops. Lepidosaurs were common too – the earliest known snake, Diablophis, was present in the same area as Ornitholestes; there were also lizards like Dorsetisaurus, Paramacellodus, and Saurillodon; and tuatara relatives like Eilenodon, Opisthias, and Theretairus. There was also a Choristodere, Cteniiogenys. But, the big stars of the Morrison aren’t any sort of reptile – not even dinosaurs – but rather, the mammals. The Morrison showcases Mammalian evolution in the late Jurassic, and has mamals from across the whole group at that point in time. A lot of these would have made good food for Ornitholestes, though they came in a wide variety of shapes and sizes and ease-of-catching. There was Amphidon, Tinodon, Aploconodon, Comodon, Trioracodon, Ctenacodon, Glirodon, Priacodon, Psalodon, Docodon, Fruitafossor, Amblotherium, Archaeotrigon, Comotherium, Dryolestes, Euthalastus, Laolestes, Paurodon, and Tathiodon – just to name a few. There was an early frog, Enneabatrachus, and an early salamander, Iridotriton, as well, and some grasshoppers.

The Lake Como Member of Wyoming was much less intense, and much less diverse. Coelurus and another early coelurosaur, Tanycolagreus, were present here; as well as the large predator Allosaurus. Sauropods included Brachiosaurus, Brontosaurus, Camarasaurus, Galeamopus, and Diplodocus. Ornithischians included Dryosaurus, Stegosaurus, and Camptosaurus. There were a few non-dinosaurs as well: the turtle Glyptops, and the stem-crocodiles Eutretauranosuchus and Goniopholis. So, similar to the Brushy Basin – but more sparse, possibly reflecting some sort of environmental change or extinction, or – since it was mostly concurrent with the Brushy Basin, and only sometimes a little bit younger – a more harsh environment than the general location of the Brushy Basin.

Other: Ornitholestes is probably more famous than it deserves to be thanks to Walking With Dinosaurs. I mean, seriously guys, this thing is really only known from like, one confirmed and two possible skeletons. It was not common. But it is still pretty cool.

~ By Meig Dickson

Sources 

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