Researchers at the University of Bath and the Natural History Museum in London conducted a new analysis that disproves the claim that dinosaurs were in decline before the massive asteroid impact that led to the extinction of most species on Earth. Researchers believe that had the asteroid collision not occurred, the dinosaurs might have continued to dominate Earth. At the time of an asteroid collision at the end of the Late Cretaceous, dinosaurs were scattered all over the world.
Before the asteroid impact, dinosaurs occupied every continent on planet Earth and were the dominant form of the animal in most terrestrial ecosystems. Despite their wide diversity, paleontologists still argue whether the diversity of dinosaurs decreased when they became extinct. The researchers collected a collection of different dinosaur family trees and used statistical modeling to assess whether each major dinosaur group was still capable of producing new species at that time.
The study found that, unlike some previous studies, the dinosaurs were not in decay before the asteroid collision. The authors also suggest that if the impact had not occurred, then dinosaurs might have continued to be the dominant group of land animals on the planet. Researcher Joe Bunsur is the lead author of the study and says that previous studies by others used different methods to arrive at their conclusions that dinosaurs would have died even if the asteroid impact had not occurred.
The new study emerges with an expanded dataset to include modern times With the wider family trees and a wide range of dinosaur species, the results do not all point to this conclusion. Bonsur says only about half of the results indicate that dinosaurs were declining. The researchers used statistical methods to overcome sample biases looking at the speciation rates of dinosaur families rather than simply counting the number of species within a family.
The main point of the paper is that it is not as simple as looking at a few trees and making a decision. Bonsur says there are inevitable large biases in the fossil record, and the lack of data often shows a decline in species, but that decline may not reflect the reality of the time.