New US Dinosaur That Lived Just Before Mass Extinction Revealed

Paleontologists have identified a previously unknown species of dinosaur that lived in North America just before the mass extinction event around 66 million years ago.

This catastrophic event wiped out the majority of plant and animal species on Earth, including all non-avian dinosaurs—marking the end of the Cretaceous period. It is thought to have resulted from the impact of a giant asteroid.

A team of researchers described the new dinosaur species in a study published in the journal PLOS ONE. The creature likely stood roughly 3 feet tall at the hip and may have weighed between around 130 and 216 pounds—similar to a human—Kyle Atkins-Weltman, one of the authors of the study with Oklahoma State University, told Newsweek.

The species forms part of a group known as the Oviraptorosaurs, which were very bird-like dinosaurs that lived during the Cretaceous (around 145 million to 66 million years ago) in North America and Asia.

"[Oviraptorosaurs] had complex feathers, long legs, short tails, and later members had toothless beaks," Atkins-Weltman said.

The new species, which has been named Eoneophron infernalis, lived at the very end of the Cretaceous, between 68-66.5 million years ago. This name roughly equates to the phrase "Pharaoh's dawn chicken from hell."

The first word in the name, which refers to the dinosaur's genus (or group of species), is derived from the ancient Greek term eo (meaning "dawn") as well as the genus name of the Egyptian vulture, Neophron—sometimes referred to as the "pharaoh's chicken." The second word in the new species name derives from the Latin word for hell, a reference to where the fossils used to describe the new dinosaur were found.

These fossils, representing a partial hindlimb, were initially uncovered in Meade County, South Dakota. The authors of the latest study subsequently obtained them from a private collector. This area forms part of the Hell Creek geological formation, which stretches over portions of Montana, North Dakota, South Dakota and Wyoming.

"The Hell Creek formation is significant because it preserves the very last dinosaurs to ever roam western North America," Atkins-Weltman said. "There are not a great deal of dinosaur-bearing formations outside that region that also include the impact layer, so formations like the Hell Creek give us an opportunity to glimpse the very end of the age of dinosaurs."

E. infernalis primarily differs from its larger, more completely-known cousin Anzu wyliei (similarly nicknamed the "chicken from hell") primarily through characteristics in the ankle, which would not be visible in life. Anzu was first described in 2014, also based on fossils from the Hell Creek Formation.

"Like Anzu, [E. infernalis] would have had a short tail, long arms with feathered wings and grasping hands, and a toothless beak. It would have also had a bony crest on its head, again, similar to Anzu, though it may have differed in exact shape," Atkins-Weltman said.

Both Anzu and the new species belong to a family within the Oviraptorosaur group known as the caenagnathids. These dinosaurs are not particularly well-known because their remains are scarce and often fragmentary—particularly from North America.

"I'd say, based on what we do have, these animals were opportunistic omnivores, with some species tending more towards carnivory—specifically eating small animals that they could swallow whole—while others may have been more herbivorous. Since these animals didn't have teeth, it's much harder to assess their diet," Atkins-Weltman said.

The discovery of the new species is significant because some researchers argue that dinosaurs were decreasing in diversity towards the very end of the Cretaceous and that the asteroid impact was just the finishing blow in a gradual extinction.

But the latest study found not only the new species but also evidence for a third, as yet unnamed caenagnathid species from Hell Creek—in addition to Anzu and E. infernalis—from this period. The evidence for this possible third species was found when the researchers reanalyzed some material in the collections of the Museum of the Rockies in Bozeman, Montana, that was previously deemed to represent Anzu. They found that this material did not match up with Anzu or the new species.

"In earlier fossil formations such as the Dinosaur Park [in Alberta, Canada], we find three caenagnathids as well—each of comparable size to one of the species we found. This indicates that this group of dinosaurs was not decreasing in diversity during that time period, and offers compelling evidence against the 'gradual extinction' model—at least for this group," Atkins-Weltman said.

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