Nanningosaurus dashiensis

By José Carlos Cortés

Etymology: Nanning City Reptile 

First Described By: Mo et al., 2007 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea, Hadrosauromorpha, Hadrosauridae, Euhadrosauria, Lambeosaurinae 

Status: Extinct

Time and Place: Sometime in the Maastrichtian age of the Late Cretaceous, between 72 and 66 million years ago 

Nanningosaurus is known from the Dashi Site in Guangxi, China 

Physical Description: Nanningosaurus is, sadly, only known from a very incomplete and partial skeleton, which does include parts of the skull and jaws. Thus, it is difficult to say what it would have looked like beyond being a Hadrosaur. It seems most likely that it was a Lambeosaurine, or Hollow-Crested Hadrosaur, though of course we don’t know if it actually had a crest or not. As such, all we can know is that it would have been a fairly bulky animal, covered in scales, with a duck-like beak and potential display or communication structures on its head. It also may have had hooves, like other hadrosaurs, on its front feet. Because of course they did. 

Diet: Being a hadrosaur, Nanningosaurus would have mainly fed upon soft, wet plants, such as those found around or in sources of water. It would have then used its thousands of teeth to mash it up into a paste, to make the leaves easier to swallow. 

Behavior: Obviously, we don’t know a lot about the behavior of Nanningosaurus because, again, we don’t have a lot of fossils of it. As hadrosaurs, they would have been very social animals, living in large herds. It would have taken care of its young, potentially in communal nesting grounds with large mounds to hold the eggs in and rotting vegetation to keep the eggs warm. It probably would have had somewhat complex social displays, potentially using color and sound, in order to communicate with other members of the herd and to find mates. It also may have used this communication to warn the herd of predators, though no predators were found with Nanningosaurus. 

Ecosystem: Nanningosaurus is not known from a very well studied fossil site – it doesn’t even have a formation name! It does seem to have been a muddy environment, indicating some sort of source of fresh water and probable frequent rains. Here, Nanningosaurus lived alongside the titanosaur Qingxiusaurus, which is also only known from limited remains. 

Other: While the exact nature of Nanningosaurus is rather murky, it is a very important fossil discovery – it’s one of the most Southern Asian Hadrosaurs! As such, as we learn more about it, we will be able to piece together the evolutionary puzzle of this wonderful dinosaur group a little clearer. 

~ By Meig Dickson

Sources Under the Cut 

Osmakasaurus depressus

By Jack Wood

Etymology: Reptile from the Canyon  

First Described By: McDonald, 2011 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna 

Status: Extinct 

Time and Place: Between 140 and 137 million years ago, from the Berriasian to the Valanginian ages of the Early Cretaceous 

Osmakasaurus is known from the Chilson member of the Lakota Formation in South Dakota 

Physical Description: Osmakasaurus was an animal fairly like Camptosaurus, a bulky bipedal herbivore with short arms and thick legs. It probably ranged between 4 and 5 meters long, and compared to its close relatives it had a fairly narrow and weirdly-shaped hip, though of course very little else is known of it to determine how else it may have differed from its close relatives. Osmakasaurus would have been primarily scaly, though it may have had some residual tufts of feathers or a feather cape of some sort for display. 

Diet: Osmakasaurus would have been a mid-level browser, feeding on bushes and low-lying tree branches, probably specializing on tough vegetation like its close relatives. 

Behavior: Osmakasaurus probably wasn’t a herding sort of animal – dinosaurs in this group of Ornithopods tend to be more solitary than the earlier flocks of small bipedal friends and the later magnificent herds of the later hadrosaurs. Instead, Osmakasaurus would have been fairly solitary, moving around its environment and trying to stick to places of denser vegetation in order to stay hidden. It is possible that it formed family groups during the mating season – it almost decidedly took care of its young, so it is not unreasonable to suppose that mated pairs would care for the young during the season together, but that would probably be the extent of its social behavior after leaving the families. They would have been somewhat slow animals, given their size, but able to run when needed. 

Ecosystem: The Chilson environment was a sandy floodplain, filled with winding rivers and greatly affected by seasonal ebbs and flows of water. As such it was mainly filled with plants able to deal with these changes – hardy conifers and seed ferns, though there were some leptosporangiate ferns as well. These rivers, though fickle, hosted a wide variety of animals in addition to Osmakasaurus. There were many types of fish, as well as mammals such as Bolodon, Passumys, Lakotalestes, and Infernolestes. Other dinosaurs mainly included other herbivores – an ankylosaur, Hoplitosaurus; some sort of large sauropod; and a more Iguanodon-like Ornithopod, Dakotodon. 

Other: Osmakasaurus used to be a species of Camptosaurus, since the latter was a wastebasket taxon in which large, bipedal ornithopods that weren’t quite Iguanodon-like enough were dumped into. It was since separated out, but not much more has been said about it. It was close to being Iguanodon, but not quite, and so still was in the group of generic-Camptosaurus-esque things. It is only known from scattered remains. 

~ By Meig Dickson

Sources under the Cut 

Maiasaura peeblesorum

By José Carlos Cortés

Etymology: Good Mother Reptile 

First Described By: Horner & Makela, 1979 

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea, Hadrosauromorpha, Hadrosauridae, Euhadrosauria, Saurolophinae, Brachylophosaurini 

Status: Extinct 

Time and Place: Between 77.2 and 76.3 million years ago, in the Campanian of the Late Cretaceous 

Maiasaura is known from the Upper member of the Two Medicine Formation in Montana 

Physical Description: Maiasaura was a medium-sized hadrosaur – aka, a “duck-billed” dinosaur. Famed for being known from hundreds of individual skeletons, we have a general idea of the appearance of this dinosaur at every stage of its life cycle. Baby Maiasaura were around 0.4 meters in length and were positively tiny in weight, weighing less than 250 kilograms. These babies were adorable in appearance: with large eyes, small heads, and small limbs. The limbs were very weak and skinny at this point in life. Despite this extremely small size, Maiasaura young grew quickly – growing to 1.5 meters in length by the first year, and reaching sexual maturity at about the age of three or so, when they weighed around 1250 kilograms. Full skeletal maturity then came at about five years of age. At this point, Maiasaura were as much as 3000 kilograms in weight, and reaching 9 meters in length. Maiasaura adults were much beefier than the young – with thick, strong hind legs and somewhat more gracile front legs, it was almost as if they had deer front legs and elephant hind legs. The front feet formed hoof-like structures – with the pinky and thumb both sticking out, the middle three fingers were fused together. The hind limbs were typical ornithopod feet, with three toes splayed out like that of a very thick bird. Their tails were thick and muscular, and their torsos also very beefy. They had very thick, muscular necks as well. 

By Ripley Cook

The heads of Maiasaura were rectangular and long, with flattened duck bills in the front. In the jaws, there were rows upon rows of densely packed teeth, forming a single surface. This surface was essentially serrated with the number of teeth packed in there. The upper jaws could then expand, allowing the lower jaws to slide upwards into them, creating a chewing motion. The more duck-like front bill was used to snip off plants and bring them into the jaw. Maiasaura also had a very large nose, forming a sort of lump in the front of the snout – this would have helped keep the head cool, and also allowed Maiasaura to make a variety of calls without a hollow crest attached. Above the eyes the skull of Maiasaura was domed with the brain area. In front of the eyes, on the top of the skull, there was a little ridged crest for display. It is logical to suppose that said crest would be somewhat patterned or even colorful, for display. 

By Nobu Tamura, CC BY 3.0

Scale impressions from Maiasaura are known. Adults of this species were entirely scaley, with almost a pebble-like texture of scales covering the entire body. These small round patches didn’t seem to overlap much, but were densely packed and not leaving much in the way of bare skin showing. Very small ones no longer than 2 millimeters were interspersed with bigger, more hexagonal ones at five to ten millimeters long. It is possible that fuzz would extend between the scales, but they would have looked rather like plants growing between sidewalk scales, and fairly impossible to see ultimately. The back was bumpy from the spine, and rather high over the animal – making Maiasaura itself quite tall. The scales were even bigger on this portion of the animal. Though skin impressions are known from Maiasaura adults and close relatives, baby Maiasaura do not have preserved skin impressions. What this means is that, while it seems very logical they’d also be scaly, there is a possibility they were fluffy to stay warm, given their smaller size. We present one hypothetical reconstruction of such for you all below, with the caveat that it is purely speculation at this time. 

By Diane Ramic

Diet: Maiasaura, like other hadrosaurs, fed mainly on soft, wet vegetation at low and middle levels of browsing (rather more tough, hard, dry vegetation like scrub plants and desert brush). So, it would favor leaves, berries, and more tender shoots, as well as plants in sources of water. 

By Madchester, in the Public Domain

Behavior: Maiasaura was a highly social, active animal – warm blooded in energy levels, these dinosaurs would have spent most of their time, each and every day, wandering around looking for food and socializing with other members of the herd. They spent a good portion of their time taking care of their young, of course, but that was only during the breeding season. Nests were made in large breeding colonies, not unlike their modern bird relatives such as seabirds, with gaps between nests only 7 meters long – less than the length of the adults that had to move between them! Between thirty and forty eggs were laid in a dense spiral pattern, and these eggs were the size of an ostrich’s today. Rotting vegetation was placed upon the nest to keep it warm. The babies, not able to take care of themselves upon hatching, entirely relied on their parents to bring them back chewed up food and look out for their safety. Sadly, most of the young would still die in the first year of life – mainly due to disease and predation, up to 90% of the young would die in the first year of life. Still, the parents did their best – with the young having features associated with cuteness, indicating dependence on the parents for survival until they reached larger sizes. 

By Debivort, CC BY-SA 3.0

Past that point, however, as the young grew faster, they fared better in terms of mortality – dropping down to 12% mortality until reaching old age again. They began to move on their own and keep up with the herd as it moved about. Young Maiasaura would walk on two legs, and as they got heavier they would switch to four, still sometimes only using the hind limbs when needed. Upon reaching sexual maturity at around three years of age, they began to get even bulkier. The Maiasaura would live in herds hundreds of individuals large, which would have been very noisy – using those bulky nostrils to make very loud, differing calls. Come mating time, they would display to each other with the ridges on their heads and other patterns. It is uncertain who was in charge of caring for the young, as sexual dimorphism isn’t seen in the skeletons of Maiasaura – if it was just the mother, both parents, just the father, or even the parents and previous children, we do not know at this time. The herd structure would protect the young, the sick, and the old from predators, and they would probably call to each other to ensure that they stayed safe in the face of predation. That being said, most of the rest of Maiasaura would then die in old age, with the death rate jumping up to 44% at the oldest ages of 12 to 14, when their own weight, slowness, and illness would leave them more vulnerable to predators. 

By Fabrizio De Rossi, retrieved from Earth Archives

Ecosystem: The Two Medicine Formation was one of the most iconic dinosaur ecosystems of all time, sort of a precursor in many ways to the more famous Hell Creek, but with more variety and dinosaur diversity! Here was a very large floodplain, filled with rivers and deltas and associated plantlife on sandy riverbanks. This environment was highly associated with the ever-present Western Interior Seaway, much like the later Hell Creek. It was seasonally arid, with rainshadows from the nearby Cordilleran Highlands, which may have been at least somewhat volcanic. This made the Two Medicine Environment positively volatile – with flash flooding, droughts, dehydration, and volcanic activity all allowing for the animals in this region to be wonderfully preserved (allowing us to know so much about Maiasaura)! Plants would grow very rapidly each wet season, making the area a very lush habitat for about half the year, allowing for all these dinosaurs to congregate here. This environment was filled with conifers and pine trees primarily, though there were also other types of plants as well. There were non-dinosaurs here as well – the pterosaurs Montanazhdarcho and Piksi, the Choristodere Champsosaurus, unnamed crocodylians, lizards like Magnuviator, mammals such as Cimexomys, Paracimexomys and Alphadon, and a wide variety of turtles like Basilemys. 

By Sam Stanton

Still, dinosaurs were the primary feature of the later (Upper) Two Medicine environment where Maiasaura frequented. There were four different types of Ceratopsians: the flat-nosed Achelosaurus, the curved-horned Einiosaurus, the giant-horned Rubeosaurus/Styracosaurus (depending on who you talk to, lumping-wise), and the small herbivore Prenoceratops. Ankylosaurs came in three different varieties – the large-spined but wiggle-taled Edmontonia, and the wide tail-clubbed Dyoplosaurus and Scolosaurus. Other hadrosaurs shared this environment with Maiasaura, like the large-nosed Gryposaurus, the round-crested Hypacrosaurus, and the small pointed crest having Prosaurolophus. There was also the small, active burrower Orodromeus. As for theropods, there were two different raptors – Bambiraptor and Richardoestesia – which would have been major problems for younger Maiasaura and the babies and eggs. The predatory opposite-bird, Gettyia, would have also been a predator of these smaller individauls. The troodontid Saurornitholestes would have been a major danger to these young Maiasaura along with its close cousins. The adults, on the other hand, had not one but two different species of tyrannosaur to contend with: the bulky and rarer Daspletosaurus, and the more slender Gorgosaurus that has been hypothesized to feed more on hadrosaurs than its cousin (though this is under hot debate). In short, this was the place to be to see just how diverse and fascinating non-avian dinosaurs were right at the end of their tenure, and Maiasaura was a major part (if not the most common part) of that ecosystem. 

By Scott Reid

Other: Maiasaura is the closest thing non-avian dinosaurs get to a “model organism” – a creature with enough specimens, research, and data about it to use it as an example for other animals which we know less about. With hundreds of specimens found and counting, we have recorded a complete growth sequence of this dinosaur, knowing what the trajectory of a typical Maiasaura life was like. This is of vital importance, as hadrosaurs were some of the most diverse dinosaurs at the end of the Cretaceous – the end of the time of non-avian forms. It is also fascinating for how much the life history of Maiasaura – a dinosaur not close to being a bird by any stretch of the imagination – is so similar to birds. With similar rapid growth rates as their warm-blooded cousins, and similar nesting and group living strategies, Maiasaura showcases how complex behavior and lifestyles were common over the entirety of the dinosaur group. Maiasaura is also of fundamental importance because, with its discovery and descriptions in the late 1970s, it served with Deinonychus to show how dinosaurs weren’t slow, sluggish, giant lizards – but active, warm-blooded avian precursors. Dinosaurs were active, behaviorally complex, and took care of their young – something that was a truly revolutionary statement before these dinosaurs were named! So, despite not really looking like much, Maiasaura is probably one of the most important dinosaur discoveries ever found. Maiasaura itself is closely related to dinosaurs such as Brachylophosaurus, and is in general part of the “crestless” hadrosaur group, along with the contemporary Gryposaurus and the later Edmontosaurus. 

~ By Meig Dickson

Sources under the Cut 

Ouranosaurus nigeriensis

By José Carlos Cortés

Etymology: Brave Reptile of the Sky 

First Described By: Taquet, 1976

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes

Status: Extinct 

Time and Place: Sometime around 112 million years ago, in the Albian age of the Early Cretaceous 

Ouranosaurus is known from the Elrhaz Formation of Agadez, Niger 

Physical Description: Ouranosaurus is an exceptionally iconic dinosaur, primarily because of its very weird distinguishing physical feature: it has a sail. Probably. The reason for this idea is that Ouranosaurus had extremely high spines on its back, reacting a notable ridge along the center of the animal. These spines become thicker and flatten as they go along the body, and bony (ossified) tendons ran across the spines and the tail. The spines grew biggest over the forelimbs, rather than over the hips. This structure may have been a sail; it also could have been a hump contain muscle or fat – similar to living bison and camels. This would have allowed for the storage of energy during the dry season or another time of year. If a sail, this structure would have been primarily one of display, flashing colors and patterns to communicate with other members of the species. It had very long forelimbs with lightly built hands, which had sharp thumb claws and the middle fingers built into a broad hoof-like structure. In short, it was capable of quadrupedal walking. It had very robust hindlimbs as well, and thus was able to walk bipedally in addition to quadrupedally. Ouranosaurus was quite large, reaching 7 meters in length and weighing somewhere around 2.2 tonnes – despite its length, it was fairly lightly built. With its sail, it was just under 3 meters tall. Being of such large size, it is unlikely that Ouranosaurus retained any fluffy covering; if it did, it was sparse and mainly ornamental.  

By Slate Weasel, in the Public Domain

It had a very long, flat head, with an even longer snout that greatly surpassed the size of Ouranosaurus’ close relative, Iguanodon. It had a straight beak, rather than a curved one, and no teeth in the front of its snout. The snout also was covered in a sheath of horn, which made it wider and more like something of a beak. This beak was then followed by densely packed batteries of teeth in the cheeks, forming a single surface like those found in the much later Hadrosaurs. The jaws had fairly weak muscles, but this was made up for with a narrow back of the skull, which made the bite ability of the jaws greater to make up for the weak musculature. In short, Ouranosaurus, despite having a very different head than the later Hadrosaurs, was still a strong chewer. Interestingly enough, the eyebrows of Ouranosaurus featured small rounded horns – making Ouranosaurus the only known Ornithopod (Hadrosaurs and their close relatives) with horns. It had highly placed nostrils, and two small bumps between the nose and the eye socket for display. 

By Pavel Riha CC BY-SA 3.0

Diet: Ouranosaurus Primarily fed on leaves, fruit, and seeds, using its chewing to break up tougher plant material and to gain food from it. Given its decent height, Ouranosaurus would have been a mid-level browser. 

By Audrey M. Horn, CC BY-SA 4.0

Behavior: Ouranosaurus would have spent most of its time foraging on a variety of plants in its ecosystem, wandering about the river delta searching for leaves, fruits, and other delicious foods. It is fairly unlikely that Ouranosaurus would have been a herding animal, as herds seemed to have been more of a behavior for Ornithopods more closely related to Hadrosaurs; instead, Ouranosaurus probably wandered about its environment alone, or in small family groups. That said, it almost certainly took care of its young in some capacity, and it did have complex social behaviors if the sail was a sail and used for display – and it used those bumps and horns on its head for display as well. It was also probably at least somewhat vocal. As for the spiked thumbs, those could have been used for defense, as well as in-fighting amongst members of the group. It wouldn’t have been a good runner, but it would have moved on two legs when needing to move at least somewhat faster, and stuck to four legs for most movements throughout the day. It probably would have used that narrow head to selectively grab a variety of foods from in between more dense foliage. 

By Scott Reid

Ecosystem: Ouranosaurus lived in an extensive river delta, filled with extensive waterways and wetlands. These wide rivers were home to many animals, including a truly extensive number of dinosaurs. Plenty of trees, including ginkgoes and pines, and some flowering plants, in addition to horsetails and ferns, were present for Ouranosaurus to feed on. There were many types of fish and invertebrates, and the turtle Taquetochelys, but the archosaurs were the main stars of the show. There was the duck-croc Anatosuchus, the giant croc Sarcosuchus, and the running croc Araripesuchus on the Crocodylomorph side of things. There was a weirdo sauropod here too, the duck-billed Nigersaurus, which decidedly does not get enough press. As for other ornithopods, there was the fast-running biped Elrhazosaurus, and a close cousin of Ouranosaurus – Lurdusaurus, an equally-weird creature, with a long neck like a sauropod and the ability to live semi-aquatically in the river system. As for theropods, there was the possible Ornithomimosaur Afromimus, the mid-zied carnosaur Eocarcharia, the Abelisaurid Kryptops, and the spinosaur Suchomimus. You will note that Ouranosaurus did not live with Spinosaurus. This is a misconception. The two did not live together – never, not once, not even close, they are not found in the same place. Spinosaurus (probably) comes from later, and while it seems that it did live that southward, it decidedly did not live in the Elrhaz formation, because its job was being done by Suchomimus. As for predators, Ouranosaurus probably had to mostly watch out for Eocarcharia and Kryptops, as they would have been the main land predators of the area. 

By Ripley Cook

Other: Ouranosaurus, being a Hadrosauriform, was most closely related to one of the more famous Ornithopods, Iguanodon, and shared the thumb spike in common with it. Interestingly enough, Ouranosaurus wasn’t the only hump or sail backed dinosaur at that point of the family tree; Morelladon, which lived much earlier, also supported some sort of odd structure on its back. 

~ By Meig Dickson

Sources under the Cut 

Jinzhousaurus yangi

By José Carlos Cortés

Etymology: Reptile from Jinzhou

First Described By: Wang & Xu, 2001

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea

Status: Extinct

Time and Place: Jinzhousaurus lived about 124.4 million years ago, in the Aptian of the Early Cretaceous 

Jinzhousaurus is known from the Dawangzhangzi Beds of the Yixian Formation

Physical Description: Jinzhousaurus was a Hadrosauroid, a type of dinosaur closely related to the duck-billed dinosaurs (Hadrosaurids) of the late Cretaceous – and a member of the group from which they evolved. This group experimented a lot with how they chewed and acquired food, mainly in order to deal with the rapidly changing environment of the Cretaceous Period. As the late Cretaceous turned into a very humid landscape, however, most of these forms died out, giving way to the Hadrosaurids to take over with their specialized-for-mushy-plant-food mouths. Jinzhousaurus was a fairly medium-sized dinosaur, reaching about 7 meters in length with a skull a half a meter long. It had very large nose holes and a wide back of the skull, with a small crest. It probably would have moved back and forth between walking on two legs versus four. It had three toes on each foot and five fingers on each hand, though only the first three fingers had claws – so it wasn’t really evolving the hoof-like front limbs seen in the Hadrosaurids proper. Its snout wasn’t a duckbill, but more like that of Iguanodon, with a rounded bulky beak – but different enough that it probably had a different feeding strategy than its cousin. Its back was stiffened extensively, making it rigid for balance and the tail mainly inflexible.

Diet: Jinzhousaurus primarily ate plants at the medium-browsing level – so mainly coniferous trees and the like.

Behavior: Jinzhousaurus probably didn’t live in groups but, rather, was mainly solitary. It would have spent most of its time wandering through its environment, grazing on plants alone, and remaining vigilant for danger. It also probably would have taken care of its young, though little else is known about its behavior. 

By Scott Reid

Ecosystem: Jinzhousaurus lived in the Yixian Formation, a highly diverse ecosystem showcasing the variety and evolution of birdie dinosaurs at the beginning of the Cretaceous period. This was a diverse coniferous forest in a temperate, seasonal climate. Very humid, it’s likely that Jinzhousaurus would have seen snow on a regular basis. There were notable dry seasons as well, leading to more tough vegetation for Jinzhousaurus to chew on. There were many flowering plants there too, along with ferns, horsetails, ginkgoes, cycads, seed ferns, and so many others – all good food for Jinzhousaurus. This was also a dense freshwater lake environment, with abundant minerals due to volcanic eruptions – leading to periodic environmental turnover.

Jinzhousaurus lived alongside many other kinds of dinosaurs, as this was an exceptionally diverse community. Here there was the ankylosaurid Liaoningosaurus, another ornithopod called Bolong, and an unnamed titanosaur in terms of other herbivores. There were many kinds of small fluffy dinosaurs – the Compsognathid Sinosauropteryx; the raptors Zhenyuanlong, Changyuraptor, Sinornithosaurus, and Tianyuraptor; the Troodontid Jianianhualong; the protobirds Jeholornis, Confuciusornis, and Zhongornis; the Anchiornithid Yixianosaurus; the Opposite Birds Dalingheornis and Shanweiniao; and the early nearly-true-birds Archaeorhynchus, Eogranivora, Yanornis, Hongshanornis, and Longicrusavis. Non-dinosaurs were of course also present – many types of fish, amphibians, and lizards; mammals such as Akidolestes, Sinobaatar, Sinodelphys, Chaoyangodens, and the famous Eomaia; Choristoderes like Hyphalosaurus and Monjurosuchus; and pterosaurs like Cathayopterus and Ningchengopterus. Essentially, a beautiful snapshot of the Early Cretaceous.

Other: Jinzhousaurus is sort of a mix between earlier ornithopods and the later hadrosaurs, so its classification was difficult to place for a while. But now it seems to be a basal member of the group that lead to the Hadrosaurids, rather than more close to Iguanodon proper.

~ By Meig Dickson

Sources under the Cut 

Angulomastacator daviesi

By José Carlos Cortés

Etymology: Bended Chewer

First Described By: Wagner & Lehman, 2009

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea, Hadrosauromorpha, HadrosauridaeEuhadrosauria, Lambeosaurinae

Status: Extinct

Time and Place: All we know is that Angulomastacator lived in the Campanian age, so sometime between 84 and 72 million years ago (though it seems to be around 76 million years ago) 

Angulomastacator is known from the Aguja Formation of Texas 

Physical Description: Angulomastacator was a Lambeosaurine – a duck-billed dinosaur with a hollow crest connected to its nose – known from its jaws. Fascinatingly enough, its jaws were weirdly curved downwards, at a 45 degree angle – unusual for a hadrosaur, or really for any dinosaur. As such, it was probably a very highly specialized herbivore. Unfortunately, without more fossil evidence of Angulomastacator, we cannot be certain of the rest of its morphology; what shape its crest may have been, or size of its body, is uncertain. As a Lambeosaurine, it would have been a rather chunky animal, and facultatively bipedal. It probably would have been of moderate to larger size.

Diet: Angulomastacator would have eaten primarily soft plant matter such as ferns and flowers and fruit, but with its downturned jaw it’s uncertain how its diet would have differed extensively from other hadrosaurs; it’s probable that it would have fed on lower lying vegetation than other hadrosaurs, reaching down into a fern and grabbing the leaves while pulling upwards. 

By Ripley Cook

Behavior: Angulomastacator, as a hadrosaur, would have been extremely social, living in very large and complicated family groups. These groups would have cooperatively taken care of their young in large nesting sites. They probably had hollow crests, which would have made distinctive sounds; though the shape of said crest is uncertain. Finally, that crest would probably have been used in display.

Ecosystem: The Aguja Formation represented a coastal plain environment, associated with a muddy transition going from the ocean to narrow river channels. This was an environment filled with many early flowering plants as they grew along the coast. Here there were many other dinosaurs – ceratopsians such as Agujaceratops and Yehuecauhceratops, ankylosaurs like Edmontonia, the pacycephalosaur Texacephale, and another hadrosaur, Kritosaurus. There were also predators such as Saurornitholestes, and omnivores like Leptorhynchos, which would have been dangers for young Angulomastacator. In addition there were turtles and the extremely big crocodilian Deinosuchus which would have fed on adult Angulomastacator as they passed by sources of water.

Other: Angulomastactor is a rare example of a hollow-crested hadrosaur with an interesting feature that isn’t the crest!

~ By Meig Dickson

Sources under the Cut 

Parasaurolophus

P. cyrtocristatus by Scott Reid

Etymology: Near Crested Reptile

First Described By: Parks, 1922

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea, Hadrosauromorpha, HadrosauridaeEuhadrosauria, Lambeosaurinae, Parasaurolophini

Referred Species: P. walkeri, P. tubicen, P. cyrtocristatus

Status: Extinct

Time and Place: Between 76.9 and 73.5 million years ago, in the Campanian age of the Late Cretaceous 

Parasaurolophus was a widespread genus of hadrosaur, living in four of the iconic formations of the Campanian of North America. Parasaurolophus is known from the Lower member of the Dinosaur Park Formation; the Middle member of the Kaiparowits Formation, the Fossil Forest Member of the Fruitland Formation, and the De-na-zin member of the Kirtland Formation. 

Physical Description: Parasaurolophus is an iconic hadrosaur – a group of highly social dinosaurs that were facultatively bipedal, mainly walking on two legs but able to walk on four limbs when necessary (and when moving slower – two legs was more for running). Like other hadrosaurs, while its hand limbs were like those of other ornithopods – kind of bulky, with three toes – its forelimbs were skinny and narrow, culminating in fused fingers that formed a pseudo-hoof structure – essentially, the limbs of hadrosaurs were what you would get if you had a mammal that was front-horse and back-rhino! Roughly speaking anyway. These hands still had their palms facing inwards – it never made “bunny hands” as commonly depicted. It was large and bulky, though how bulky is up to some debate – with some scientists rendering it more slender in the neck and tail regions for more streamlined running; and others rendering it very bulky in the neck and tail, for fat storage and general weight to help it defend itself from predators. Unfortunately, this is one of those speculations that seems unlikely to be solved anytime soon! In addition to that, it had somewhat high neural spines, giving its back even more bulk and muscle mass. Overall, Parasaurolophus was about 9.5 meters long, and weighed 2.5 tonnes – making it a very large hadrosaur in general, with one of the tallest backs of any hadrosaur. 

By Marmelad, CC BY-SA 2.5

Naturally, its bulk and weird proportions aren’t the things that stand out about Parasaurolophus – its crest is. This was a long tube extending off the back of the head, connected to the nose and beak via hollow tubes running from the nostrils through the crest. This crest varied in shape from species to species, with notable extremes – really long and straight, or short and very curved. This shape did not vary based on sex. What the crest was used for, we’ll get into more in the behavior section. In addition it had a large head in general, with a duck-like bill in the front of the mouth, and rows and rows and rows of densely packed teeth. This battery of tooth formed a single surface, kind of like a serrated edge, that helped Parasaurolophus chew! The upper jaw of Parasaurolophus would extend outwards somewhat, allowing the lower jaw to slide into the upper jaw, thus slicing up soft vegetation so it can be easily digested.

Parasaurolophus was externally covered in scales, which were tubercle-like and uniformly spaced out over the entire body. Other details of its coloration and external appearance are not currently known. 

P. walkeri by Leandra Walkers, Phil Senter, and James H. Robins; CC BY 2.5

Diet: Parasaurolophus, like other hadrosaurs, was a low to medium level browser, feeding mainly on soft and wet plants – even those associated with water environments like lakes, swamps, and rivers; though it wouldn’t have lived in the water as was suggested decades ago. As a Lambeosaurine, it was a selective forager, eating just the right plants and fruit – Saurolophines, the non-crested hadrosaurs, were more generalist browsers.

Behavior: Parasaurolophus was a herding animal, living in large social groups that took care of each other and their young. They would have stuck together in these large groups, migrating back and forth extensively along the Western Interior Seaway. Like other hadrosaurs, it would have taken care of its young in large colonies of nests, with parents working together to bring food back to the altricial nestlings. The nests were made in mounds, with vegetation used to keep the eggs warm. The babies, interestingly enough, didn’t have any crests – in fact, baby hadrosaurs more or less looked very similar, with differences between the species coming into play during puberty. These animals first grew rapidly to larger sizes, before growing the crest, leading to an awkward tween stage in which the animal looked like a full-grown Parasaurolophus without the crest. 

P. walkeri by Ripley Cook

This emphasizes something important about Parasaurolophus – sexual communication. The crest, in addition to the function I’ll address shortly, was very much a display structure. That weird shape and differences from species to species emphasized the distinctions between them, allowing for mating partners to identify each other. Brighter colors on the crest would indicate the individual was able to waste resources on color (and, potentially, color that would out them to predators – making them better able to defend themselves, as well) and, thus, a better option for mating. What colors the crests were is uncertain, but given these were herbivores, bright fancy colors brought about from diet are certainly possible – and ones brought about structurally through scales are also in the realm of possibility. While it has been hypothesized that Parasaurolophus had a skin flap between the crest and the neck, this would have severely limited neck flexibility, and seems unlikely.

Now: did the crest have other functions besides display? Absolutely. Right now, the leading hypothesis for the crest is that it was essentially a Shofar (hollow bone used as horn) attached to the noses of Parasaurolophus. This means that Parasaurolophus could breathe in air through the nostrils, send it through the passageways in the crest like some sort of trombone, and blow it back out – making very loud, very eerie, honking sounds. These sounds varied from species to species, both within Parasaurolophus and beyond, as other hadrosaurs also had a variety of hollow crests and tube pathways – and each differently shaped tube would produce a different sound. It’s uncertain what this sound would have been exactly, given we don’t know what – if any – external ornamentation was on the crest that would affect the sound output, but modeling has been done to mimic what it would sound like without any ornamentation, and it’s as creepy and awesome as one would expect:

Parasaurolophus Calls

These calls would have been used in communication between members of the herd, and also for mating calls and warning calls. A variety of sounds could have been made from the crest, allowing for somewhat complex communication. This showcases the sheer diversity of vocal structures evolved in dinosaurs! Only time will tell how many cool sounds and functions these crests in all crested hadrosaurs could have had. 

By Brittany Bostain

Ecosystem: Parasaurolophus lived in a variety of ecosystems, each an iconic fauna of the Campanian of the Late Cretaceous. These environments were all along the Western Interior Seaway, however, there were some notable differences amongst them, since they were at different latitudes and thus experienced variations in water levels and temperature.

The coldest environment, the Dinosaur Park Formation, was where P. walkeri lived. Here, Parasaurolophus lived in a large series of river channels forming very wet floodplains that constantly flooded and very wet in general. This was a very rich environment, filled to the brim with a variety of conifers, horsetails, ferns, and flowering plants. Parasaurolophus lived in the lower section of the formation, which I like to call an Ornithischian Lover’s dream come true. Here, there were ankylosaurs aplenty – Edmontonia, Euoplocephalus, Dyoplosaurus, Platypelta, and Scolosaurus; hadrosaurs like Gryposaurus and Corythosaurus; pachycephalosaurs like Hanssuesia, Stegoceras and Foraminacephale; and ceratopsians like Chasmosaurus, Mercuriceratops, and Spinops. There were non-ornithischians too, of course – the tyrannosaur Gorgosaurus which would have been the biggest predator of Parasaurolophus; the ornithomimosaurs Rativates and Struthiomimus; the raptors Dromaeosaurus and Sauronitholestes that would have hunted the eggs and babies of Parasaurolophus; and the troodontid Stenonychosaurus which would have also been a real pest. Plus there were plenty of non-dinosaurs – sharks, sturgeon fish, gars, and teleosts; bivalves and gastropods; multituberculates, proto-marsupials, and proto-placentals; crocodilians, choristoderes, lizards, turtles, pterosaurs, and even plesiosaurs. 

Kaiparowits Teratophoneus and P. cyrtocristatus, by ДиБгд, in the Public Domain

The more temperate environment, the Kaiparowits Formation, was a very muddy environment, with an extreme number of plants leading it to be called a jungle environment – with a wide diversity of new animals very unique to the ecosystem. Here is where P. cyrtocristatus lived – the weirdest of the three species – along with a lot of other truly weird dinosaurs. In the Middle Unit of the formation, Parasaurolophus lived with the ankylosaur Akainacephalus, the hadrosaur Gryposaurus, the ceratopsians Nasutoceratops and Kosmoceratops, the tyrannosaur Teratophoneus, the ornithomimid Ornithomimus, and the troodontid Talos. Here it was Teratophoneus that would have been the main predator of Parasaurolophus. There was also an enantiornithine, Mirarce, and an Oviraptorosaur, Hagryphus. As for non-dinosaurs, there were plenty of turtles and crocodylomorphs.

Finally, the hotter environments of P. tubicen were similar to each other, with one coming after the other. The Fruitland Formation was slightly earlier, and here Parasaurolophus is known from the later Fossil Forest Member, which was a swampy environment next to the sea, and very warm and forested. Parasaurolophus was joined by the pachycephalosaur Stegoceras, the ceratopsian Pentaceratps, as well as unnamed dromaeosaurs, ornithomimds, troodontids, and tyrannosaurids. The later Kirtland Formation also had Parasaurolophus, in the same area, and the same species, indicating that P. tubicen was largely unaffected by the environmental transition. Parasaurolophus is known here from the lowest De-na-zin Member, which was a series of braided river floodplains and not as muddy as the earlier formation (but still very wet). Here Parasaurolophus was joined by the ankylosaurs Ziapelta and Nodocephalosaurus, the hadrosaurs Naashoibitosaurus Kritosaurus, the pachycephalosaur Sphaerotholus, the ceratopsian Pentaceratops, the titanosaur Alamosaurus, and the raptor Saurornitholestes. 

P. tubicen by José Carlos Cortés

Other: Parasaurolophus was named as such because it was thought to be superficially similar to Saurolophus, a Saurolophine with a non-hollow crest coming off the back of its head; it actually took us a bit to realize “hollow crested hadrosaurs” were a major group!

Species Differences: Parasaurolophus had three species, each somewhat different from the others. P. walkeri comes from the Dinosaur Park Formation, P. tubicen from the Kirtland Formation, and P. cyrtocristatus from the Fruitland and Kaiparowits Formations. This makes P. walkeri the oldest of the three, P. cyrtocristatus the middle species, and P. tubicen the youngest. P. walkeri was relatively average between the two; P. cyrtocristatus had the small, curved crest; and P. tubicen was the largest of the species (with both P. tubicen and P. walkeri have long, trombone-like crests). (Though really all three crests were shofarim).

~ By Meig Dickson

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Zhanghenglong yangchengensis

By Jack Wood

Etymology: Dragon from Zhang Heng

First Described By: Xing et al., 2014

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna, Hadrosauriformes, Hadrosauroidea

Status: Extinct

Time and Place: 85 million years ago, in the Santonian age of the Late Cretaceous 

Zhanghenglong is known from the Majiacun Formation in Xixia, Henan, China 

Physical Description: Zhanghenglong was a Hadrosauroid, a type of ornithopod that includes Hadrosaurs (the duck-billed dinosaurs) and all of their closest relatives. As such, Zhanghenglong was a large, facultatively quadrupedal animal, with an enormous torso. It had a thick neck and tail with a short, squat head; very sturdy back limbs, and front limbs not unlike a horse, with toes mashed together a little like a hoof. Uniquely amongst this group, Zhanghenglong had high spines along its back, creating a ridge going from the back through the tail. Being close to Hadrosaurs themselves, they also had similar teeth to Hadrosaurs, adapted for feeding on soft plant material, with rows of teeth forming ridges in the mouth good for chewing. This evolution of the specialized feeding structure of hadrosaurs – the “battery” of teeth as it were – correlated strongly with a transition in environmental conditions from a drier to a wetter climate, and with it, softer plant material that needed more chewing to cut up, but weren’t as rough on the teeth. This allowed dinosaurs like Zhanghenglong and the hadrosaurs proper to take the place of other Hadrosauroids, as they were better positioned to eat soft, wet plants rather than hard, dry plants as earlier Hadrosauroids had eaten. Zhanghenglong was a medium sized hadrosauroid, not going over 7 meters in length and 2 meters in height.

Diet: Zhanghenglong primarily fed upon wet plant material such as those found in ponds, swamps, and wet forests. 

By Scott Reid

Behavior: As a hadrosauroid only known from two individuals, it seems unlikely that Zhanghenglong was a herding animal – herding had lost its appeal in the “middle” Cretaceous ornithopod group, before reappearing in the hadrosaurs of the later Cretaceous. Instead, Zhanghenglong would have kept more to itself, foraging on plant material in its environment only in smaller family groups or on its own.

Still, as a dinosaur, it probably took care of its young, though fossils of juveniles and babies are needed to better understand the behavior of Zhanghenglong on that front. Being found in a fossil bone bed where many eggshells have been recovered, it seems possible that we might know more about its breeding behavior before long. It probably would have been very territorial over nests and young, given the presence of small predators in the area; but it might not have been very skittish overall, as there were few large predators present.

Ecosystem: The Majiacun Formation is a poorly known environment from China in the early-late Cretaceous, with a few (but not many) dinosaurs known from it. The environment was a small floodplain, but it’s uncertain what kind of plants were present; presumably, softer plants rather than hard desert foliage. Here, Zhanghenglong lived alongside the alvarezsaur Xixianykus, the troodont Xixiasaurus, a potential Baryonychine, the informally named ornithopod “Bakesaurus”, and the informally named titanosaur “Yunxianosaurus”. Hopefully, more studies of this area will reveal what other dinosaurs Zhanghenglong lived with.

Other: Zhanghenglong, in addition to having the specialized structures of hadrosaurids, lived around the same time that the first hadrosaurs began to really take off, indicating its importance in understanding the preliminary evolution of this iconic dinosaur group.

~ By Meig Dickson

Sources 

Tan, Q.-W., H. Xing, Y.-G. Hu, L. Tan, and X. Xing. 2015. New hadrosauroid material from the Upper Cretaceous Majiacun Formation of Hubei Province, central China. Vertebrata PalAsiatica 53(3):245-264

Xing, H., D. Wang, F. Han, C. Sullivan, Q. Ma, Y. He, D. W. E. Hone, R. Yan, F. Du, X. Xu. 2014. A new basal Hadrosauroid dinosaur (Dinosauria: Ornithopoda) with transitional features from the Late Cretaceous of Henan Province, China. PLoS One 9(6): e98821.

Xu, X., D.-Y. Wang, C. Sullivan, D. W. E. Hone, F.-L. Han, R.-H. Yan, and F.-M. Du. 2010. A basal parvicursorine (Theropoda: Alvarezsauridae) from the Upper Cretaceous of China. Zootaxa 2413:1-19

Zhou, S.-q., and Z.-j. Feng. 2002. [Studies on the occurrence beds of Oölithus and their relations to the upper-lower boundarues in Henan province]. Resources Survey & Environment 23(1):68-76

 

Iguanacolossus fortis

By José Carlos Cortés

Etymology: Colossal Iguana

First Described By: McDonald et al., 2010

Classification: Dinosauromorpha, Dinosauriformes, Dracohors, Dinosauria, Ornithischia, Genasauria, Neornithischia, Cerapoda, Ornithopoda, Iguanodontia, Dryomorpha, Ankylopollexia, Styracosterna

Status: Extinct

Time and Place: Between 129 and 123 million years ago, sometime between the Barremian and Aptian ages of the Early Cretaceous

Iguanacolossus is known from the Yellow Cat Member of the Cedar Mountain Formation in Utah 

Physical Description: Iguanacolossus was a large, bipedal herbivore, similar in general shape to the earlier Camptosaurus from the same region of North America. As its name would suggest, it was fairly large and robust, reaching 9 meters long and 3 meters in height at the hip – making it longer than the width of a truck and much taller than a person. Known from decent, if scattered, remains, we have parts of the legs, tail, hips, back, and skull. However, we do not have the hands of this dinosaur; though it was touted as being a thumb-spiked dinosaur, we can’t actually be certain it had a large one; most members of the group have reduced thumbs spikes, rather than the large and distinctive structure of Iguanodon itself.

Iguanacolossus had a long, narrow skull, filled with teeth for chewing up plant material, and a beak to aid in snipping off leaves prior to chewing. Its teeth had thickened enamel, to aid in chewing. Iguanacolossus would have slid its lower jaw into its upper jaw to chew, using the serrations created by the closely packed teeth to slice up the plant material. Iguanacolossus would have had a thickened tail to aid in walking, and a thick, muscular neck.

Though only one specimen of Iguanacolossus is officially described, more specimens from juveniles and subadults are known and assigned to the genus in a thesis publication; an official peer-reviewed article is necessary to definitively assign these bones to Iguanacolossus, but for now the association seems likely given they come from the same time and place, and they have similar morphologies. These skeletons indicate that Iguanacolossus went through very rapid growth during development, aiding in reaching such a large size. This also helps to point to Iguanacolossus being warm-blooded and active (as is probably the case for all dinosaurs). In fact, Iguanacolossus shows growth patterns similar to the later Maiasaura, indicating that hadrosaur-like growth and development evolved quickly in their family tree.

Given its large size and relatives with scales, Iguanacolossus would have been mostly, if not entirely, scaly. Any feathers left on its body would have been ornamental – for display only.

Diet: Medium-level browser of plant material; Iguanacolossus would have been able to eat tough vegetation given its increased chewing abilities and strong enamel. 

By Lukas Panzarin, CC BY 2.5

Behavior: Given that Iguanacolossus was found with one single specimen, and its relative Iguanodon was actually a fairly solitary animal, it’s likely that Iguanacolossus would have traveled and fed alone in its environment, only congregating into groups to take care of its young. It’s possible, however, given the probable group of juveniles collected elsewhere, that the young did congregate together until reaching maturity. Their large size at this point would have allowed Iguanacolossus to take care of itself just fine without help from other members of the herd. This would have allowed individual Iguanacolossus to find more food on its own, which, combined with its ability to chew tough plant material, indicates at least some seasonal changes in vegetation that reduced the amount of soft plants to eat.

Ecosystem: Given the presence of extensive mudstone and other evidence of water in the Yellow Cat Member, this represented a fairly wet time in the history of the region, as opposed to other times in the Cedar Mountain Formation or the early Morrison Formation that were marked with extensive arid climates. Lakes and rivers filled the floodplain region and provided a variety of habitats for Iguanacolossus to move around in. Still, it would have been semi-arid, and its possible that the mudstones were the result of seasonal changes in water level.

Iguanacolossus shared its environment with a variety other dinosaurs, including the other Ornithopods Hippodraco and Cedrorestes; the ankylosaur Gastonia; the sauropods Mierasaurus and Cedarosaurus; the early Therizinosaurs Martharaptor and Falcarius; the large (and weird) Dromaeosaur Utahraptor and the somewhat more normal Dromaeosaur Yurgovuchia; the Troodontid Geminiraptor; and the early Ornithomimosaur Nedcolbertia.

Non-dinosaurs were present as well, of course – notably the tuatara relative Toxolophosaurus, turtles such as Glyptops; multiple types of fish; and the mammal Cifelliodon.

Other: Iguanacolossus may have been able to walk quadrupedally, but that’s difficult to determine without forelimb fossils.

~ By Meig Dickson

Sources 

Burton, D., B. W. Greenhalgh, B. B. Britt, B. J. Kowallis, W. S. Elliot, R. Barrick. 2006. New radiometric ages from the Cedar Mountain Formation, Utah and the Cloverly Formation, Wyoming: implications for contained dinosaur faunas. Geological SOciety of America Abstracts with Programs 38 (7): 52.

Carpenter, K. 2006. Assessing Dinosaur Faunal Turnover in the Cedar Mountain Formation (Lower Cretaceous) of Eastern Utah, USA. Mesozoic Terrestrial Ecosystems 21 – 25.

Garrison, J. R., D. B. Brinkman, D. J. Nichols, P. Layer, D. L. Burge and D. Thayn. 2007. A multidisciplinary study of the Lower Cretaceous Cedar Mountain Formation, Mussentuchit Wash, Utah: a determination of the paleoenvironment and paleoecology of the Eolambia caroljonesa dinosaur quarry. Cretaceous Research 28:461-494

Kirkland, J.I., S. K.Madsen. 2007. The Lower Cretaceous Cedar Mountain Formation, eastern Utah: the view up an always interesting learning curve. Fieldtrip Guidebook, Geological Society of America, Rocky Mountain Section. 1-108 p.

McDonald, A. T., J. I. Kirkland, D. D. DeBlieux, S. K. Madsen, J. Cavin, A. R. C. Milner, L. Panzarin. 2010. New basal iguanodonts from the Cedar Mountain Formation of Utah and the evolution of thumb-spiked dinosaurs. PLoS One 5 (11): e14075: 1 – 35.

Miller, R. D. 2016. The Lower Cretaceous Cedar Mountain Formation of eastern Utah: A Comparison with the Coeval Burro Canyon Formation, Including New Measured Sections on the Upcompahgre Uplift. UtahState University All Graduate Plan B and other Reports: 829.

Sartin, C. E. 2017. An Osteohistologic Analysis of Growth in Ornithopoda. Johns Hopkins University Graduate Thesis.