A rare North American dinosaur named after a two-faced Roman god

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About 100 million years ago in what is now Utah, a 10-foot-long (3-meter-long) cousin of the duck-billed dinosaur crushed tough plant stems and leaves with its powerful teeth and powerful jaws.

Chewing was probably too busy to notice that the once familiar world around him was shifting. But for the scientists who recently described this newly discovered species, its fossils provide clues about life during the middle Cretaceous period (145 million to 66 million years ago), as rising air temperatures and sea levels reshaped Earth’s lush habitats.

One of the first ornithopods was a plant-eater – a group of herbivorous, mostly bipedal dinosaurs. By the end of the Cretaceous, Ornithopods had become the most successful vegetarians of the era, including duck-billed hadrosaurs, sometimes called “cows of the Cretaceous” and crested Parasaurolophus, among others.

Ornithopods first appeared during the Jurassic period (201.3 million to 145 million years ago) and although the early species were common across North America, populations dwindled and died out as the Earth warmed. These new fossils provide evidence that some early lineages persisted despite climate change, researchers report June 7 in the journal Plus one.

The analysis of the bones surprised them—the animal appeared to be a close relative of rhabdodontomorphs, a species of ornithopod previously known almost entirely from European fossils.

The newly discovered species, named Iani (YAH-nee) Smithy, is the first early ornithopod from this part of the Cretaceous period to be discovered in North America. It’s an important find because it offers a glimpse into a time in North America about which very little is known about the continent’s dinosaurs, said Darla Zelenitsky, associate professor in the Department of Earth Sciences at the University of Calgary in Canada.

“This new fossil indicates that rhabdodon-like ornithopods were more diverse and stayed in North America longer than previously expected,” Zelenitsky, who was not involved in the study, told CNN in an email.

The dinosaur’s genus name – ianni – is a nod to its changing world. The study authors stated that it refers to the two-faced Janus, the Roman god of transformations.

Study lead author Lindsay Zanno, chair of paleontology at the North Carolina Museum of Natural Science and research associate professor of biological sciences at North Carolina State University in Raleigh, said paleontologists excavated the fossils in 2015 at a site called the Mussentuchit Member in southern Utah. .

The bones included a skull, some ribs, vertebrae, limb bones, and parts of the pelvis. Well-preserved Cretaceous skulls from this part of North America are extremely rare; The area once bordered a vast inland sea, Zano told CNN in an email, and bones fossilize poorly in the coastal humidity.

“Most of the specimens we find in mossentoshet are very fragmentary or in jagged form,” Zano said. By comparison, these fossils were in such good condition that the researchers were able to identify the specimen as a juvenile.

“The bones of the spine don’t fuse together, which leaves room for them to grow,” Zano explained.

Since rhabdodontomorphs are known almost exclusively from Europe (with some possible species identified in Australia), scientists weren’t expecting to find one in late Cretaceous sediments in North America.

However, a number of features in the animal are similar to those in rhabdodontomorphs, including its unique cheekbones; Large, deeply recessed teeth and an opening site in the skull for the artery. Other features, such as the shape of the brain and palate, and the positions of the teeth toward the front of the face, indicate that it was a new species.

Because I. smithi is a primitive ornithopod, it could provide clues about how the group fared during the late Cretaceous period, Zelenitsky said in the email.

Hadrosaurs, which evolved tens of millions of years after I. smithi, adapted to share ecosystems with dinosaurs, and are some of the fiercest predators of all. They were able to do this without the benefit of the horns or shields that protected other herbivorous dinosaurs, Zelenitsky said.

“Ornithopod species may have evolved a certain way or adopted certain behaviors to succeed,” she said. “Primitive forms, like Iani, are close to the root of the ornithopod evolutionary tree and will certainly provide some answers.”

The I. Smithy fossils also provide an important puzzle piece from a time in Earth’s past when climate change altered the planet, extinguishing many species of North American dinosaurs. Zano added that preserved remains from such times could offer valuable insights into navigating an increasingly warming world today.

“The more we can understand how these changes affected ancient animals, the better we can prepare ourselves for what we will face in the future.”