Andrew Flynn, a professor at New Mexico State University, has dedicated his research to understanding the events surrounding the mass extinction that eliminated the dinosaurs. This investigation, initiated during his Ph.D. at Baylor University in Texas, has progressed since 2013 and recently culminated in findings published in the journal Science on October 23.
Flynn is the lead author of a study titled “Late-surviving New Mexican dinosaurs illuminate high-end Cretaceous diversity and provinciality,” which offers fresh insights into the last dinosaur-dominated ecosystems in the San Juan Basin of northwestern New Mexico. The research focuses on the last non-avian dinosaurs found in the Naashoibito member of the De-Na-Zin Wilderness Area, located near Farmington.
Approximately 66 million years ago, an asteroid impact in the Yucatan Peninsula resulted in the extinction of about 75% of Earth”s species, including all dinosaurs except for birds, which are their modern descendants. Flynn noted, “The Naashoibito dinosaurs coexisted with the well-known Hell Creek species in Montana and the Dakotas. They were thriving and forming vibrant, diverse communities.”
In contrast to the well-documented dinosaur species from the Hell Creek region, such as Triceratops and Edmontosaurus, New Mexico”s dinosaur fauna is primarily represented by the massive long-necked sauropod Alamosaurus. Estimates place the Alamosaurus at a length comparable to two semi-truck trailers, weighing between 30 to 80 tons, with a height of approximately 30 to 50 feet. It is similar in size to a blue whale, albeit lighter.
Flynn”s research indicates that the New Mexico dinosaurs, which differ significantly from those found in Wyoming and North Dakota, date back to the same period. “What our new research reveals is that these dinosaurs were not in decline as they approached the mass extinction; they were flourishing. The asteroid impact appears to have abruptly ended their existence,” he stated. This finding challenges the widely accepted notion that there was a prolonged decline in dinosaur diversity leading up to the extinction event.
Another significant discovery is that the mammals that survived the extinction retained distinct north and south biogeographical provinces, contrasting with other mass extinction events where species distributions tended to be more uniform.
Throughout Earth”s geological history, the magnetic field has undergone reversals, alternating between normal and reversed states. Scientists can utilize these magnetic field changes to determine the age of rock deposits. Flynn and his colleagues evaluated the magnetic pole directions of the rock formations, alongside geochemical dating of sandstones, which confirmed that the dinosaur fossils unearthed in northern New Mexico are contemporaneous with those from the Hell Creek Formation in North Dakota and Montana.
Steve Brusatte, a professor of paleontology and evolution at the University of Edinburgh and a co-author of the study, remarked, “The extinction of the dinosaurs represents one of the most significant mass die-offs in Earth”s history. Prior to this research, paleontologists had limited access to fossils of dinosaurs that were precisely dated to the last few hundred thousand years of the Cretaceous before the asteroid impact.”
Brusatte emphasized, “Now, we have fossils from New Mexico that existed right at the end. These dinosaurs encountered the asteroid. When we compare these fossils with those from further north, it becomes clear that there was a rich diversity of dinosaur species thriving until the asteroid”s impact.”
Flynn concluded, “We can definitively show that these dinosaurs are from the very end of the Cretaceous, with our findings revealing that these rocks were formed within the last 380,000 years of that period.” His future research will focus on locating fossil plants within the Naashoibito Member. “As a trained paleobotanist, my interest lies in studying fossil plants. Discovering these fossilized remains will allow us to compare flora before and after the extinction event in New Mexico,” he explained. “While we have a solid understanding of post-extinction flora, the pre-extinction landscape remains elusive. Our efforts to find these fossil plants have yet to yield results, but that does not mean they are absent.”
