The most renowned mass extinction in Earth’s history occurred approximately 66 million years ago. A swift decline in environmental conditions resulted in the extinction of around 75% of species, including the most famous non-avian dinosaurs, and the eventual restoration of terrestrial ecosystems. The ongoing debate focuses on whether dinosaurs vanished abruptly while they were still diverse and thriving or whether they experienced a prolonged decline by the end of the Cretaceous.
Flynn and colleagues analyzed Alamosaurus fossils found in northwestern New Mexico, revealing that these dinosaurs, while very different, are contemporaneous with those discovered further north in Wyoming and Montana. Image credit: Natalia Jagielska.
The geological formations of northwestern New Mexico hold a concealed chapter of Earth’s history.
Paleontologist Daniel Peppe from Baylor University and his team have uncovered indications of a flourishing dinosaur ecosystem in the Kirtland Formation’s Naashoibito Formation just prior to the asteroid impact.
Utilizing high-precision dating methods, they established that the fossils in these formations range from 66.4 to 66 million years old.
“The Naashoibito dinosaur coexisted with the renowned Hell Creek species of Montana and the Dakotas,” Dr. Peppe remarked.
“They were not in decline; rather, they constituted a vibrant, diverse community.”
The discoveries in New Mexico challenge previous assumptions.
Instead of being uniform and weakened, dinosaur communities across North America were unique and thriving in their respective regions.
Through ecological and biogeographic analysis, the researchers determined that dinosaurs in western North America thrived in distinct biozones shaped by regional temperature variations, rather than geographical barriers like mountains or rivers.
“Our recent study indicates that dinosaurs were not on the brink of mass extinction,” stated Andrew Flynn, a researcher at New Mexico State University.
“They were thriving, but the asteroid impact ultimately led to their demise.”
“This contradicts the long-established notion that a gradual decline in dinosaur diversity precipitated mass extinction, making them more susceptible to extinction.”
“The asteroid impact briefly terminated the age of dinosaurs, but the ecosystem they left laid the groundwork for what followed.”
“Within 300,000 years post-extinction, mammals began to diversify rapidly, branching into new diets, body sizes, and ecological roles.”
“The same temperature-driven patterns that influenced dinosaur communities carried into the Paleocene, illustrating how climate influenced the rebirth of life following catastrophic events.”
“The surviving mammals continued to exhibit distinct northern and southern biological regions.”
“Mammals from the north and south are markedly different from each other, diverging from other mass extinctions, which tend to appear more uniform.”
Of findings posted in today’s edition of Science.
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Andrew G. Flynn et al.. 2025. Late-surviving neo-Mexican dinosaurs reveal Cretaceous superlative diversity and locality. Science 390 (6771): 400-404; doi: 10.1126/science.adw3282
Source: www.sci.news
