While it's generally established that dinosaurs went extinct as a result of an asteroid strike about 66 million years ago, scientists have debated about whether the creatures were still thriving in the lead-up to the extinction event, or already on the decline due to millions of years of climate change. A new paper published Wednesday in the journal Nature Communications appears to back up the former theory.
As summarized by Phys.org, the researchers behind the new study concluded that, based on analysis of species distribution and environmental changes in North America around the time of the dinosaurs' extinction, there's a good chance the creatures were not in a state of decline at the time of the asteroid impact. In a statement quoted by the outlet, Imperial College London doctoral student and study lead author Alessandro Chiarenza explained that dinosaurs might have been quite resilient despite the threat of climate change, contrary to what some prior studies had suggested.
"The results of our study suggest that dinosaurs as a whole were adaptable animals, capable of coping with the environmental changes and climatic fluctuations that happened during the last few million years of the Late Cretaceous. Climate change over prolonged time scales did not cause a long-term decline of dinosaurs through the last stages of this period."Much like in the case of the aforementioned studies, the researchers started by analyzing fossil records, this time focusing on North America due to the large number of Late Cretaceous fossils preserved on the continent. As North America was then divided into two halves by an inland sea, Chiarenza and his colleagues found that the western half was far more conducive to fossilization than the eastern half because of the presence of sediment from what would eventually become the Rocky Mountains. The researchers' methodologies also included the use of "ecological niche" modeling, which predicts rainfall, temperature, and other metrics that need to be at a certain level for species to survive. This technique was then used to determine where certain environmental conditions would occur over time across ancient North America, thus giving the researchers an idea of the areas where dinosaur species would have been able to properly cope with the changing climate.
Based on these techniques, the researchers concluded that the eastern half of North America had more habitats that could support several dinosaur groups at once, though as noted above, this part of the continent was less likely than the western half to preserve fossils. Additionally, the areas that were thought to be "dinosaur-rich" at specific points in time were smaller whenever such a condition was met, making it even harder for fossils to be discovered in modern times.
"Most of what we know about Late Cretaceous North American dinosaurs comes from an area smaller than one-third of the present-day continent, and yet we know that dinosaurs roamed all across North America, from Alaska to New Jersey and down to Mexico," said University College London researcher and study co-author Phillip Mannion.