The last days of the dinosaurs were not as quiet as many believed. A recent study published in Science shows that just before the asteroid impact that wiped them out 66 million years ago, dinosaurs were thriving in their ecosystems. Researchers from Baylor University, New Mexico State University, the Smithsonian Institution, and other partners conducted this exciting research, changing what we know about dinosaur extinction.
In northwestern New Mexico, fossil discoveries from the Naashoibito Member of the Kirtland Formation provide a snapshot of this vibrant period. These fossils date from about 66.4 to 66 million years ago, right at the Cretaceous–Paleogene boundary, challenging the idea that dinosaurs were on their way out.
“The Naashoibito dinosaurs lived at the same time as the famous Hell Creek species in Montana and the Dakotas,” said Daniel Peppe, Ph.D., from Baylor University. “They were not in decline – these were vibrant, diverse communities.”
The fossils revealed a bustling environment filled with titanosaurs, hadrosaurs, and ceratopsians, not a world in decline but one rich in life and complexity. This evidence suggests that these dinosaurs were not just surviving; they were thriving up until the dreadful asteroid strike that changed everything.
According to the findings in Science, researchers compared fossil records from New Mexico, Wyoming, and Montana. They discovered distinct areas, called bioprovinces, where different dinosaur species thrived depending on local climates rather than physical barriers like mountains or rivers. This means that each region had a unique mix of species suited to their specific environments.
“What our new research shows is that dinosaurs are not on their way out going into the mass extinction,” said Andrew Flynn, Ph.D., from New Mexico State University. “They’re doing great, they’re thriving, and the asteroid impact seems to knock them out.”
This shift in understanding overturns decades of thinking. Rather than a slow decline, the end of the dinosaurs seems to have been quick and catastrophic. The asteroid didn’t just wipe out a weakened population; it obliterated a thriving one.
After the impact, mammals evolved quickly to fill the ecological gaps left behind. Interestingly, the unique climate zones established during the time of the dinosaurs continued to influence mammal development in the Paleocene epoch. This suggests that the ecological frameworks shaped by dinosaurs played a role in how life bounced back after the disaster.
“The surviving mammals still retain the same north and south bioprovinces,” Flynn added. “Mammals in the north and the south are very different, which differs from other mass extinctions.”
This continuity hints that while the asteroid led to a mass extinction, it didn’t completely erase the existing ecological structures. The legacy of dinosaur ecosystems helped guide life’s recovery post-impact, shaping the future of mammals and other species.
The findings not only reshape our understanding of dinosaurs but also remind us that changes in our ecosystems can have lasting effects, much like the dinosaurs left behind a complicated legacy in the wake of their sudden end. For more insights, check out the study in Science [here](https://www.science.org/doi/10.1126/science.adw3282).
