NMSU geologist leads study suggesting dinosaurs were thriving in North America before asteroid strike

LAS CRUCES — A geology professor who joined the New Mexico State University faculty this year is the lead author of a new paper addressing a long-standing question about the extinction of dinosaurs.

Research dating back to 1980 has linked the extinction of non-avian dinosaurs to an asteroid striking Earth 66 million years ago.

Scientists have identified the collision’s ground zero as the 125-mile-wide Chicxulub crater, in the Yucatán Peninsula in southeast Mexico.

The asteroid, believed to be seven miles in width, struck the planet with the force of about 100 million megatons, triggering shock waves, tsunamis, earthquakes and dust that blocked sunlight and altered the climate. The event eliminated 75% of the Earth’s species.

A question that remained was whether dinosaurs were already in decline when the collision happened. A research paper published Thursday in the journal Science, with New Mexico State University geologist Andrew Flynn as lead author, suggests they were thriving up to the collision.

“What our new research shows is that dinosaurs are not on their way out going into the mass extinction,” Flynn said in a written statement. “They’re doing great, they’re thriving, and … the asteroid impact seems to knock them out. This counters a long-held idea that there was this long-term decline in dinosaur diversity leading up to the mass extinction, making them more prone to extinction.”

The finding required dating fossil evidence from the Naashoibito site near Farmington, which holds evidence of numerous dinosaur species. The largest of these was the Alamosaurus, an enormous sauropod that favored warmer regions and was not present in other well-studied regions.

Flynn’s team studied the magnetic field direction and sandstone crystals from the site to establish that the New Mexico dinosaurs were contemporaries of species from sites in Montana and North Dakota, thus establishing that diverse species of dinosaurs were thriving at the same time, shortly before the asteroid struck. The team dated the rock deposits to the last 380,000 years of the Cretaceous period.

“An inconvenient truth is that until now paleontologists have had few fossils of dinosaurs unequivocally dated to the last few hundred thousand years of the Cretaceous, before the asteroid hit, so much of our understanding of the extinction was extrapolated from older fossils and statistical analyses,” co-author Steve Brusatte, a paleontologist from the University of Edinburgh School of GeoSciences, said. “Now, in New Mexico, we have fossils of dinosaurs that were there right at the end. … There clearly were many types of dinosaurs thriving up until that moment the asteroid ended it all.”

The authors say this contradicts the theory that homogeneity may have made the dinosaurs vulnerable to extinction: They were diverse, regionally distinct and apparently thriving until the sudden extinction event, the authors said.

Flynn said he began studying the mass extinction event in 2013 while a Ph.D. candidate at Baylor University in Waco, Texas. His co-authors on the new paper, titled “Late-surviving New Mexican dinosaurs illuminate high end-Cretaceous diversity and provinciality,” include researchers from New Mexico Tech, the New Mexico Museum of Natural History and Science, as well as Baylor, the University of Edinburgh and other institutions.

Flynn completed his Ph.D. with a dissertation on studies of fossil sites in New Mexico’s San Juan Basin in 2020, according to his CV. He conducted post-doctoral research at the University of Houston and the National Museum of Natural History before arriving at NMSU in 2025.

Next, Flynn said he plans to turn from dinosaurs to fossils of plant life at the Naashoibito site.

“Our previous work in this area gives us a good idea of what the flora looks like just (after the extinction), but we have no idea what it looks like just before,” Flynn said. “We’ve looked for fossil plants, but so far, we’ve never found them. It doesn’t mean they’re not there, it just means we haven’t found them yet.”