Astonishingly Well-Preserved Dinosaur Found With Fossilized Tail Feathers And Skin Tissue

An illustration of Ornithomimus based on the findings of preserved tail feathers and soft tissue. Credit: Julius Csotonyi

While studying at the University of Alberta, a first-year paleontology student stumbled across a surprisingly well-preserved dinosaur fossil, with its tail feathers and some soft tissue remarkably intact. This Ornithomimus (“bird mimic”) dinosaur, which existed in the Late Cretaceous period in what is now modern-day North America, has been described in the journal Cretaceous Research.

“This fossil was originally found in 2009,” discoverer and study author Aaron van der Reest told IFLScience. “It was collected and left to sit in storage for four years…within 20 minutes of starting work on it, I found the tail…and then some black lines I recognized,” which eventually turned out to be feather components.

This feathered, toothless reptile was a theropod (“beast feet”), a dinosaur type that’s a subset of the saurischian group of dinosaurs, a mostly carnivorous collection of ancient reptiles. All of the saurischians died out at the end of the famous asteroid-induced extinction event 65 million years ago – except, of course, the birds, their surviving descendants.

Unlike modern birds, these ancient ostrich-like creatures couldn’t fly, but probably used feathers for thermoregulation – controlling their body temperature. “Ostriches use bare skin to thermoregulate,” said Reest in a statement. “Because the plumage on this specimen is virtually identical to that of an ostrich, we can infer that Ornithomimus was likely doing the same thing, using feathered regions on their body to maintain body temperature. It would've looked a lot like an ostrich.”

The relatively excellent degree of preservation allowed the authors of this study to examine the soft tissue of the beast. As Reest explained to IFLScience: “It was probably preserved in a rapid burial by a river, covered in a fine mud with a low microbial content, protecting it from oxygen-based decomposition.”

From the mid-thigh bone down, this dinosaur had bare skin. Although the feathers were crushed by the compaction of the sediment over time, the protein structures that made up the feathers – keratin – were picked up by a scanning electron microscope, revealing a 3D feather pattern on the tail and body.

Ornithomimus forms part of a major dinosaur group (the Coelurosauria) that includes many of the saurischians, including modern-day birds. The scientific consensus is that modern-day birds evolved from the same ancestor of small, carnivorous dinosaurs called dromeosaurids, a group that existed in the same time period as the Ornithomimus.

“Dromaeosaurs lived right alongside Ornithomimus”, Reest continued. “Just last year, we found a fossil dromaeosaur, a Saurornitholestes – same region, same age.” This new discovery will no doubt help fill in more of the detail of how the Coelurosauria group evolved through time.

“This [new Ornithomimus] specimen…tightens the linkages between dinosaurs and birds, in particular with respect to theropods,” said Alex Wolfe, second author on the paper, in a statement. “There are so many components of the morphology of this fossil as well as the chemistry of the feathers that are essentially indistinguishable from modern birds.”

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