Newly Discovered Iani Smithi Dinosaur Fossil Sheds Light on Herbivore Communities in the Late Cretaceous

HETANEWS.com – The creature nicknamed Iani smithi was identified from a 99 million year old fossil. Even after two centuries of research, paleontologists still know relatively little about specific stretches of time in the Age of Dinosaurs.

Paleontologists have long wondered how famous the fauna of the late Cretaceous period were—like celebrities Triceratops, Tyrannosaurusand Ankylosaurus — appeared, but researchers have been frustrated by the scarcity of fossils in earlier time periods.

Now new dinosaurs from 99 million year old rocks in Utah are helping to fill in the fossil void. named Ian Smith after the Roman god Ianus, said in mythology to oversee the transition, and paleontologist Joshua Aaron Smith.

The newly discovered dinosaur is known from a partial skeleton that includes most of the skull as well as parts of the spine and limbs.

When alive, this plant-eating beaked creature was about 12 feet tall from the tip of its snout to the tip of its tail.

As North Carolina Museum of Natural Sciences paleontologist Lindsay Zanno and colleagues explained Wednesday at PLOS Onethese dinosaurs help decipher the changes that led to classic dinosaur communities in the Late Cretaceous.

At first glance, dinosaurs may look ordinary. Jani it lacked the horns, plates, spikes or other outstanding features we often associate with dinosaurs.

The details of the reptile skeleton are, however, identifying Jani as rhabdodontomorphs — a group of little-known herbivorous dinosaurs that were only recognized in 2016.

“I was very skeptical about the identification,” said Zanno, but the uncertainty made the researchers extra careful in their analysis.

“Skepticism is what makes good science, so I spent a long time researching our anatomy and analysis,” he added.

Jani it shares some undeniable traits with other rhabdodontomorphs, he says, most notably its teeth and skull.

This dinosaur, like Zalmox 8 feet long from Romania and Muttaburrasaurus 26 feet long from Australia, were a group of small to medium sized herbivores that spread worldwide during the Cretaceous in the earlier days. Duck-billed dinosaurs evolve.

In the broader picture of dinosaur evolution, the rhabdodontomorph is related to other iconic bipedal herbivores Iguanodon. They were a bit like the antelope or deer of their time, filling the medium-sized herbivore niche in their community.

Although such herbivores often receive less popular attention than the sharp-toothed carnivores that eat them, discoveries Jani is a key part of the ongoing, challenging effort to understand and describe the dinosaurs that experts call the Mussentuchit Member of Utah’s Cedar Mountain. .

“The Mount Cedar Formation captures more than 40 million years of dinosaur evolution in western North America,” says Zanno, making it a great place to look for broader trends in reptile history. And while “fossilized bone isn’t hard to find in the gray-green badlands of Mussentuchit,” says Zanno, well-preserved skeletons are hard to find.

For decades, these dinosaurs found in rocks essentially came to paleontologists as isolated, hard-to-identify teeth.

Teeth have allowed experts to guess the different groups of dinosaurs that existed in western North America some 99 million years ago — such as raptors, titanosaurs, and horned dinosaurs — but bones that would reveal the full identity of each dinosaur are extremely hard to find.

Years of fieldwork by Zanno and colleagues, as well as other groups of paleontologists, have begun to answer some of the question marks on the fossil.

In 2013, Zanno and colleagues named Seats of the Meekers, the Allosaurus large found in the Mussentuchit Member, and in 2019 they followed that up with a small tyrannosaurus Moros fearless. Now Jani adding a new herbivore to the mix.

“Jani certainly helped fill in gaps in the mid-Cretaceous fossil record,” said New York Institute of Technology paleontologist Karen Poole, who was not involved in the new research.

The rhabdodontomorph was originally named after discoveries in Europe, later being extended to the known fossils from Australia.

Poole and colleagues previously hypothesized that rhabdodontomorphs were present in Cretaceous North America, and the discovery from Utah adds new evidence that dinosaurs thrived there.

Paleontologists are still searching for more fossils, but from available materials, Zanno and colleagues have identified several large groups of herbivorous dinosaurs that lived side by side in eastern Utah 99 million years ago.

Jani joined the hadrosaur kin Eolambia; an as yet unnamed small, slender herbivorous species of the group called thescelosaurs; armored dinosaurs; and horned dinosaurs.

Together they represent at least five groups of herbivorous dinosaurs that were present when the classic dinosaur communities of the Late Cretaceous evolved.

“This discovery makes it clear that ornithopod dinosaurs were not on a steady path toward hadrosaurs,” said Poole, “but diversified into a wide variety of animals that all coexisted with one another.”

The cast of characters is wider and more varied than experts know. The Middle Cretaceous was also a time of ecological upheaval.

“The mid-Cretaceous North American dinosaurs took a double hit,” Zanno said.

New groups of organisms, including dinosaurs, reached North America from ancient Asia at the same time as global climate change was rapid. North American dinosaurs and ancient Asian dinosaurs mixed together, some groups thrived and others disappeared.

“I can’t help but think of it as Grand Central Station stuck in time,” says Zanno, “with different lineages of dinosaurs coming and going, and lots of chaos.”

In western North America, hadrosaurs, horned dinosaurs, armored dinosaurs and even scelosaurs survived until the end of the Cretaceous, 66 million years ago.

But Jani and his relatives died. Somehow, these medium-sized herbivores didn’t make it though the many groups around them have continued for millions of years.

When this cutoff occurred, and why, is unknown. Other places in Utah, such as Straight Cliffs in the south of the state, may contain relevant fossils to answer that question.

Popular depictions of the dinosaur era often condense the entire time period into relatively narrow slices. The entire Cretaceous period spanned about 79 million years, from 66 million to 145 million years ago.

That’s a wider span of time than the entire post-Cretaceous history of the world, and plenty of time for different groups of dinosaurs to thrive and decline.

The direct march of Early Cretaceous dinosaurs to their Late Cretaceous descendants that we love to see down the halls of museums doesn’t happen in a neat, straightforward fashion.

The story is much more complicated, involving an entire group of dinosaurs that experts have only just discovered, and Janiis actually just the tip of the Cretaceous iceberg.

“There are lots of herbivores in any ecosystem,” says Poole, “and we haven’t found all of them yet.”

Source: smithsonianmag.com