A new analysis has been performed by researchers at the University of Bath and the Natural History Museum London that refutes the claim dinosaurs were in decline before the massive asteroid impact that led to the extinction of most species on Earth. The researchers believe that had the asteroid impact not happened, dinosaurs may have continued to dominate the Earth. At the time of the asteroid impact at the end of the Late Cretaceous period, dinosaurs were widespread globally.
Prior to the asteroid impact, dinosaurs occupied every continent on the planet and were the dominant form of animal for most terrestrial ecosystems. Despite their widespread diversity, paleobiologists still argue if dinosaurs were declining in diversity when they went extinct. The researchers collected a set of different dinosaur family trees and used statistical modeling to assess if each main dinosaur group was still able to produce new species at the time.
The study found dinosaurs were not in decline before the asteroid impact, contradicting some previous studies. Authors also suggest that if the impact hadn’t occurred, dinosaurs might have continued to be the dominant group of land animals on the planet. Researcher Joe Bonsor is the lead author of the study and says that past studies done by others used various methods to come to their conclusions that dinosaurs would’ve died out even if the asteroid impact hadn’t happened.
The new study shows with an expanded data set to include more recent times with wider family trees and a wider range of dinosaur types, results don’t all point to that conclusion. Bonsor says that only about half of the results suggest dinosaurs were in decline. The researchers used statistical methods to overcome sampling biases looking at the rates of speciation of dinosaur families rather than simply counting the number of species inside a family.
The paper’s main point is that it isn’t as simple as looking at a few trees and making a decision. Bonsor says that there are large and unavoidable biases in the fossil record, and lack of data can often show a decline in species, but the decline may not reflect the reality of the time.