With the discovery of a new dinosaur species, researchers at the University of Wisconsin–Madison have challenged a long-held belief about where dinosaurs originated and how the ancient reptiles spread throughout the planet.
They published their findings Jan. 8 in the Zoological Journal of the Linnean Society.
One scientific theory has suggested dinosaurs first emerged in the southern part of the supercontinent Pangea, waiting millions of years before migrating north. That theory was based on the absence of fossils found in the north that dated back to those from the south, study authors said.
Stay informed on the latest news
Sign up for WPR’s email newsletter.
“Just because we didn’t have dinosaurs doesn’t mean they weren’t here,” said Paleontologist Dave Lovelace, a scientist at the University of Wisconsin Geology Museum and lead researcher on the study.
Lovelace and his collaborators recently announced their discovery of the oldest dinosaur in the northern hemisphere: Ahvaytum bahndooiveche.
His team spent years analyzing fossils from the new, chicken-sized dinosaur, which were found in present-day Wyoming in 2013. The researchers determined the fossils were about 230 million years old. That’s around the age of the earliest dinosaurs found in the southern hemisphere, Lovelace said.
“The bone, the animal itself, is relatively insignificant. It doesn’t look like a lot,” Lovelace said. “But the place and the time where this thing is discovered, from what geological time, is really important to the story of dinosaur evolution.”
Their finding shows that dinosaurs existed in the northern and southern hemispheres around the same time. It also challenges whether dinosaurs originated in the south at all.
“So really, it’s just showing that by the point dinosaurs show up in the fossil record, by the time we really see them, they have a pretty global distribution, ” Lovelace said.
Lovelace and his team analysed the fossils and the soil around them to determine their age and origins. They studied the shape and structure of crystals in a layer of rock above the fossils to date them.
“Kudos to the find,” said longtime paleontologist Paul Sereno, a professor at the University of Chicago who was not involved in the study. “I find the fossils very fascinating, and it does underscore that small dinosaurs were running about north and south by 230 million years.”
About 35 years ago, Sereno helped discover some of the earliest dinosaur fossils in Argentina.
“The idea that dinosaurs started in the south and migrated north, let’s say, or had some center of origin in South America or the Andes region — personally, I never believed that,” Sereno said. Afterall, the fossil record is patchwork, he added.
“Paleontology is one of these slow leaking Pandora’s boxes that just keeps on giving you stuff,” Sereno said.
In fact, dinosaurs might have been present even earlier.
“We’ve got upright footprints that predate both my dinosaurs and the ones from Wyoming,” Sereno said. “We find footprints which we think are dinosaurs, maybe the earliest ones at 250 million years.”
What did it look like?
Ahvaytum bahndooiveche was about the size of a chicken, the scientists determined from fossils of its ankle and part of its femur.
“Just those two bones tell us a huge amount about this animal,” Lovelace said. “It’s relatively small, standing just over a foot tall at the hips, it would have been relatively long, two to three feet long. So a really long tail, reasonably long neck, but not very big.”
And based on Ahvaytum’s family tree, it was probably an omnivore, he added.
The name Ahvaytum bahndooiveche, or “long ago dinosaur,” was created by study author Reba Teran, a member of the Eastern Shoshone Tribe. The site in Wyoming is on their ancestral lands.
“The fact that the animal holds the first Shoshone name for an animal is pretty special too,” Lovelace said.
Wisconsin Public Radio, © Copyright 2025, Board of Regents of the University of Wisconsin System and Wisconsin Educational Communications Board.
