Dinosaur fossils discovered by paleontologists working with the University of Wisconsin-Madison have been determined to be the oldest-known fossils, presenting evidence that the species was in existence millions of years before previously thought.
Dave Lovelace, a research scientist at the University of Wisconsin Geology Museum, co-led the expedition with Aaron Kufner, a graduate student at the university. Lovelace and Kufner discovered the fossils in 2013 nestled within the Popo Agie rock formation, located near a crater in an area previously known as Laurasia, now present-day Wyoming After more than a decade of painstaking analysis to confirm the fossils’ age and that they were actually a new species, the researchers determined that the reptile, dubbed Ahvaytum bahndooiveche, is the oldest-known Laurasian dinosaur. They estimate that the fossils are “around 230 million years old.” The findings were published Jan. 8 in the Zoological Journal of the Linnean Society.
“We have, with these fossils, the oldest equatorial dinosaur in the world—it’s also North America’s oldest dinosaur,” Lovelace told Ancient Origins.
Lovelace believes the dinosaur to be an early relative to sauropods, herbivorous dinos known as “titanosaurs” for their towering size. Ahvaytum bahndooiveche was hardly as large as its future family members, though, having lived millions of years before they fully evolved. “Ahvaytum was about the size of a big chicken, with a long tail,” Lovelace told Men’s Journal. “It would have stood a little over a foot high at the hips and about 3 feet long.”
The paleontologists used radioisotopic dating on the rocks encasing the fossil to determine the lizard’s presence 230 million years ago. In the process, they discovered “dinosaur-like” footprints in even older rocks, indicating that other dinosaur species existed a few million years before.
Lovelace explained to Men’s Journal this track “was made by an animal whose hindfoot had three toes touching the ground (tridactyl) and its middle toe was longer than the other two, which is seen in dinosaurs and their closest relatives. The tracks are most likely made by a silesaur or dino-like critter,” he continued.
“What’s significant is that [the Atreipus-Grallator] track comes from rock that is at least 234 million years old, so four or more million years older than Ahvaytum. This suggests early dinosaur-like critters (in other words, dinosaurs’ most recent ancestors) were in the Northern Hemisphere even earlier! This is also in line with evidence from the Southern Hemisphere,” Lovelace said.
Lovelace explained that he and his crew, bolstered by the Atreipus-Grallator find, “will continue to look for new fossils (both bone and tracks) and build the story of the environment, climate, and ecology. Everything we’ve found is new,” he added, “and helps expand our understanding of the dawn of dinosaurs and the early evolution of the modern fauna we know today.”
Mike Klein/University of Wisconsin-Madison