Study Shows Dinosaurs Lived Alongside Their Precursors

Graduate Students’ Findings From Dig in New Mexico Contradict Widely Held Theory
BY Erin Olivella-Wright
Contributing Writer
Monday, July 23, 2007

After years of excavating fossils in the arroyos of New Mexico, researchers published a report Friday in the journal Science explaining that dinosaurs and their precursors lived contemporaneously, despite what scholars had previously thought.

In the summer of 2005, lead excavators Randall Irmis and Sterling Nesbitt, graduate students at UC Berkeley and Columbia University, respectively, launched the project after visiting the site at Hayden Quarry. The quarry became a hotspot for archeological activity after a group of hikers discovered some fossils there in 2002.

The excavators returned in the summer of 2006 with funding from the National Geographic Society, the Theodore Roosevelt Memorial Fund and the Jurassic Foundation and came away with new discoveries about dinosaurs in the Late Triassic Period.

Before the graduate students’ discoveries, academics thought that the precursors to dinosaurs had died out before the reign of the dinosaurs, but the report says that new evidence proves this to be false.

Using uranium and lead dating from nearby sites, the researchers were able to conclude that dinosaurs were living in New Mexico alongside the basal dinosauromorphs, the precursors to the dinosaurs, for between 15 million and 20 million years.

As there are no radioactive materials in the Hayden Quarry, the authors are giving themselves a 5 million year margin of error, Irmis said.

Irmis said he is excited by the findings, as they are the first of their kind.

“This has never been found anywhere else in the world,” he said.

He stressed that while the team never found a full skeleton, there were enough fossils to deduce the differences between the dinosaurs and the basal dinosauromorphs.

“Overall, they look a lot like dinosaurs, but there are a few anatomical features that are found in the hip and the leg that are found in the dinosaurs but not the dinosaur precursors,” he said.

Nesbitt, a UC Berkeley alumnus, also said he is impressed with the results, especially given the location of the fossils.

“It’s pretty incredible because we found something that everyone didn’t expect in North America. (Now) North America is just as important for dinosaur origins as South America,” he said.

Irmis said the results of the study show that dinosaurs are prime examples of adaptive radiation and added that perhaps the most significant result of the findings is further support for the theory of evolution.

“I hope that the findings encourage other people to accept evolution as a scientific process,” he said.

Nesbitt said overall that he is pleased to have generated findings that could lead to other discoveries .

“To start the sequence of discovery is pretty neat,” he said. “(We are) going from one leg bone to revising what we know about early dinosaur evolution.”