Dinosaur Contemporaries

An artist rendition of a Late Jurassic pond, showing a small crocodilian, a lizard, several frogs, turtles, and a salamander.
Not every animal that lived in the Late Jurassic Morrison ecosystem was a dinosaur. Tiny creatures also shared their habitat.

NPS / Bob Walters and Tess Kissinger

There were many creatures who lived in the Age of Dinosaurs that weren't dinosaurs themselves. In the Carnegie Quarry, scientists found evidence of other creatures who shared the dinosaurs' habitat. Hidden among the bones of giants were thousands of clams, tiny skeletons from non-dinosaur reptiles, fragments of amphibians, fossilized plants bearing evidence of insects, and even a partial skull of a small mammal. Thanks to these special finds, scientists were able to develop a much clearer picture of the Morrison ecosystem that the dinosaurs of Dinosaur and their tiny contemporaries called home.

The Morrison Ecosystem

The dinosaurs of the Carnegie Quarry were found in the Brushy Basin member of the Morrison Rock Formation. Today, that rock layer is made of sandstone, but back in the Late Jurassic Period (about 150 million years ago), it was just sand. At that time, northeastern Utah was home to a vast, flat floodplain. Fossilized unionid clams in the rock layer provide evidence that a system of braided freshwater rivers flowed through this area. Fossilized cycads and ferns indicate that the climate was wamer and more humid than it is today. Dinosaurs roamed the landscape, but they weren't alone. Mixed among the huge bones, scientists have found evidence of the dinosaurs' contemporaries, who shared their lush habitat. These include frogs, salamanders, crocodilians, turtles, and even small mammals.
A drawing of several clams with their shells open.
Freshwater clams from the family Unionidae were found fossilized among the dinosaur bones at the Carnegie Quarry. Their presence indicates that the Morrison ecosystem was home to a river.

NPS / Molly Swindle


While dinosaurs are undoubtedly the stars of Dinosaur National Monument, mollusc fossils are far more abundant. In fact, they're the reason scientists were able to learn so much about the Morrison ecosystem the Late Jurassic dinosaurs called home. Unlike the non-avian dinosaurs, molluscs, like clams and mussels, still exist today. This makes it possible for scientists to observe them and study how they interact with their environments. The clams (specifically, Vetulonaia sp.) that were found in the Carnegie Quarry were members of the family Unionidae. This huge group of freshwater mussels still has existing members in rivers and streams all over the world today. Unionid clams require a permanent flowing water source in order to survive. To paleontologists, the presence of Unionid clams in the Carnegie Quarry strongly suggests that the Wall of Bones was once the sandy floor of a flowing freshwater riverbed.

All Unionid clams today are filter feeders. They burrow down into the sediment of their watery habitats to sift for food. Unlike vertebrates, clams dont have internal skeletons. Their insides are soft and gooey, but surrounded by hard shells that are capable of fossilizing under the right conditions. During severe droughts, when the water dries up, Unionid clams are commonly observed rising to surface. They typically open their shells in hopes of finding food. If the water doesn't return in time, they die in this position, often in huge numbers. When excavating the Carnegie Quarry, scientists found 3 instances where the clams died in large numbers with their shells open. To paleontologists, this is evidence that Late Jurassic Utah experienced at least 3 severe droughts. Because the dinosaur fossils mixed in among the clams appear to be in various states of decay, scientists believe that the droughts are what killed them. The dinosaurs of the Quarry Exhibit Hall lived in the Late Jurassic Period, about 84 million years before the non-avian dinosaurs went extinct.

Non-Dinosaur Reptiles

Just as not all fish are sharks, not all reptiles are dinosaurs. This was just as true in the Late Jurassic Period (150 million years ago) as it is today. Among the dinosaur bones of the Carnegie Quarry, scientists uncovered the fossil remains of four non-dinosaur reptiles. There were two kinds of turtles, Dinochelys whitei and Glyptops. The scientists also found a tiny crocodilian named Hoplosuchus kayi, which probably reached no more than 8 inches (20.3 cm) in length as an adult. They also uncovered a lizard-like reptile, Iridotriton hechti, which belonged to a unique order of reptiles called, Sphenodontia.
An artist interpretation of how the Jurassic turtle Dinochelys whitei may have looked. The drawing is heavily inspired by modern pond turtles.
Dinochelys whitei, a kind of Late Jurassic turtle found fossilized among the dinosaur bones at the Carnegie Quarry.

NPS / Molly Swindle


Dinochelys whitei
Dinochelys whitei was a species of turtle that lived in the Morrison ecosystem of the Late Jurassic Period (about 150 million years ago). Excavations of the Carnegie Quarry uncovered both juvenile and adult specimens of this turtle. The adult is the holotype for Dinochelys whitei. This means that it was the first of its kind ever found and scientifically described. Just like turtles today, scientists believe Dinochelys relied on its hard shell for protection. Because they're so sturdy, shells are more likely to survive the fossilization process, and are therefore the most common turtle part found as fossils. Paleontologists theorize that Dinochelys lived a life similar to that of modern river and pond turtles. It lived in or near water and probably ate plants, insects, and fish. Sadly, no skull has ever been found, so it's difficult to know for sure. Thankfully, parts of the tail, leg, and foot were well preserved.
An artist's depiction of Glyptops, a kind of Late Jurassic turtle.
Glyptops was another turtle found in the Carnegie Quarry.

NPS / Molly Swindle

Glyptops plicatulus
Glyptops plicatulus was another Late Jurassic turtle living in the Morrison ecosystem. Both an adult and juvenile were found in the Carnegie Quarry. The adult is one of the best preserved Glyptops specimens ever found. The smaller shell is one of the only well-preserved juvenile specimens of Glyptops known to science. Like Dinochelys, scientists believe Glyptops lived a life similar to that of modern turtles. It lived in or near water, and likely ate plants, insects, and/or small fish. The shells of adult and juvenile Glyptops had slightly different patterns, with the juvenile's shell having a gap that between scutes (plates) that would allow for more growth. Scientists can tell from the fossilized specimens that Glyptops was capable of retracting its head by folding its neck back vertically, just like modern-day box turtles, pond turtles, and tortoises.
A drawing of a opisithius rarus, a kind of lizard-like reptile called a sphenodont. The drawing is heavily based on a tuatara.
Opisthius rarus, was not a true lizard, but a type of lizard-like reptile called a sphenodont.

NPS / Molly Swindle

Lizard-like Reptiles

Opisthius rarus
Opisthius rarus is a lizard-like reptile that probably grew to about 1 foot (30.4 cm) long. It's not a true lizard, but a sphenodont. Sphenodontia is a separate group from squamata (the group all true lizards and snakes belong to). They're the most common land-going reptile fossils in Mesozoic-aged rocks. While it was once a very diverse group, the only sphenodont alive today is the tuatara of New Zealand. The continued existence of this special lizard-like reptile is extremely helpful to paleontologists. Because it can still be observed in life, scientists can study tuatara anatomy and behavior to learn how extinct sphenodonts, like Opisthius rarus, may have lived. Living tuataras eat worms, snails, slugs, spiders, lizards, young birds, and eggs.

Like other small vertebrates, sphenodonts have extremely fragile and delicate bones. In spite of this, several well preserved skulls have been found at the Monument. Scienctists are able to use CT scans to study these tiny specimens. The resulting high resolution images make it possible to research the bones in great detail without damaging them. It also allows them to study parts of the skeleton still buried in the rock.
A drawing of a small, running crocodilian called Hoplosuchus kayi.
Hoplosuchus kayi was a not a dinosaur, but a small crocodilian that probably reached no more than 8 inches (20 cm) in length as an adult.

NPS / Molly Swindle


Hoplosuchus kayi
The word "suchus" is Latin for crocodile, and Hoplosuchus kayi was just that: a small crocodilian. Contrary to popular belief, crocodiles and their relatives are NOT considered dinosaurs. While both dinosaurs and crocodilians came from the order Archosauria, their ancestry became divided long before dinosaurs and crocs developed their individual distinctive traits. Still, both groups lived and thrived in the Morrison ecosystem of the Late Jurassic. While the Carnegie Quarry contains abundant evidence of crocodilians, only one specimen of Hoplosuchus kayi was found. Thankfully, it was beautifully preserved! The skull, limbs, vertebrae, and armor are all present in 3-dimensional clarity. Even a century after its discovery, Hoplosuchus remains one of the most complete and well preserved small vertebrate skeletons found anywhere in the Morrison Formation.


While dinosaurs as a group of animals are certainly old, amphibians are thought to be even older. The earliest well-known amphibians appear in fossil deposits from the Devonian Period, about 360 million years ago. Most amphibians today have the ability to survive in both aquatic (water) and terrestrial (land) habitats. In fact, the Greek word amphibios means "living a double life." Today, living amphibians are represented by three major orders: the frogs and toads (Anura), salamanders (Caudata), and caecilians (Gymnophomia). Fossils from two of these groups were found in Morrison rocks of the Rainbow Park area of Dinosaur National Monument. These were some juvenile frog skeletons and the skeleton of a type of salamander known as a newt.
A drawing of a juvenile species of Late Jurassic frog called Rhadinosteus parvus.
The only specimens of Rhadinosteus parvus found at Dinosaur National Monument were juveniles still undergoing the process of metamorphosis.

NPS / Molly Swindle


Rhadinosteus parvus
Rhadinosteus parvus was a small species of frog living in the Late Jurassic Period. Its name means, "small slender bone," which makes sense because the frog was only a half inch (1 cm) long. Like other small invertebrates, frog bones tend to be extremely delicate. However, a slab of Jurassic rock uncovered at Dinosaur in the Rainbow Park area. The slab of pond deposits contained over a dozen skeletons! While they can be hard to discern, close inspection of the slab revealed that the skeletons were mostly intact. However, most of the frogs were still undergoing metamorphosis (the biological process tadpoles undertake to become adult frogs). As a result, no adult frogs were found. Still, Rhadinosteus parvus remains the only nearly-complete frog skeleton from the Morrison ecosystem. It's one of the best preserved frog specimens from the Late Jurassic. Like modern frogs, Rhadinosteus parvus was an aquatic carnivore that likely fed on insects.
A drawing of a kind of newt from the Late Jurassic preriod called Iridotriton hechti.
Iridotriton hechti was a newt that lived in the Late Jurassic Period. Fossils of it were found in the Rainbow Park area of Dinosaur National Monument.

NPS / Molly Swindle


Iridotriton hechti
Iridotriton hechti was a small species of newt that lived in the Late Jurassic period. Unlike many of the other critters on this page, it was found in the Rainbow Park area of Dinosaur National Monument. In fact, its genus name means, "rainbow newt." The species name, hechti, comes from the specimen's discoverer, Max Hecht, who studied Jurassic salamanders. Scientists think that Iridotriton hechti probably lived a life very similar to that of modern-day salamanders. It would've required a wet habitat, and probably ate insects, small invertebrates, and crustaceans.

As of 2024, the fossil of Iridotriton hechti from Dinosaur National Monument is the only specimen of Iridotriton known to science. It's also the holotype specimen for the genus, which means its the first known specimen of its kind to be found and described. Because of this, any fossils of Late Jurassic salamanders found in the future could be compared to the Iridotriton fossil from Dinosaur. If the new specimen is similar enough, it could also belong to the Iridotriton genus, or possibly even be the same species, hecti. This is how paleontologists decide which genus and species newly found fossils belong to.


While no direct body fossils of insects were found in the Carnegie Quarry, scientists did find evidence of their existence among the dinosaur bones. Most of that evidence comes from the preserved remains of dinosaur bones that still show the telltale signs of termite or beetle burrowing. Modern-day members of these insect groups have been observed burrowing into the unfossilized bones of modern animals. Entomologists (scientists who study insects) have observed some types of modern insect feeding on bone, perhaps in order to meet their bodies' nitrogen requirements, since bones are rich in nitrogen. Some insects have also been known to burrow into bone to create pupating chambers, safe spaces where the insects' babies can hatch and develop into their adult forms.


Of all the animal fossils found among the quarry dinosaur bones, mammals were some of the rarest and most surprising. By the time the Late Jurassic Period rolled around, the other animal groups on this list had been around for tens or even hundreds of millions of years. Compared to molluscs, insects, reptiles, and amphibians, mammals were the new kids on the block. Scientists believe the ancestors of mammals (synapsids) broke off from the ancestors of true reptiles (sauropsids) sometime in the Carboniferous period, well before dinosaurs existed. Thanks to fossils, we know the descendants of these unique animal groups lived together in the Morrison ecosystem. However, with dinosaurs filling all the big-bodied roles, it seems that Mesozoic mammals rarely grew larger than the size of a modern-day badger.
A drawing of a small mammal from the Late Jurassic period. It resembles a rat.
Glirodon grandis was a small mammal living in the Late Jurassic period. Although it likely had a rodent-like appearance, it was not actually a rodent.

NPS / Molly Swindle

Glirodon grandis
Despite its name meaning, "grand rodent tooth," Glirodon grandis is not thought to be a rodent. Instead, scientists believe it was a member a now-extinct order of mammals called, Multituberculata. Although not a rodent, Glirodon likely filled an environmental role very similar to that of modern rodents. It was about the size of a modern-day rat, and had enlarged upper incisors like mice and rats, too. Most Jurassic mammal fossils tend to be isolated teeth or jaw fragments.

The Glirodon grandis fossil of found at Dinosaur is only the front half of a skull with some teeth visible, but it still represents the species' holotype (the first specimen to be found and described). The Glirodon skull found at Dinosaur National Monument is one of the most complete multituberculate skulls from Late Jurassic North America.

Last updated: April 20, 2024

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