A new statistical analysis of the diversity of dinosaurs shows that they were not in decline at the time of their extinction from an asteroid struck 66 million years ago.
Researchers at the University of Bath and the Natural History Museum in London say that if the impact had not occurred, dinosaurs may have continued to dominate the Earth.
Dinosaurs were widespread worldwide during the end-of-end asteroid̵
However, it is still debated among paleobiologists whether dinosaurs declined in diversity during their extinction.
To answer this question, the research team collected a set of different dinosaur family trees and used statistical modeling to assess whether each of the major dinosaur groups was still able to produce new species at that time.
Their study published in the journal Open science of the Royal Society, found that dinosaurs were not in decline before the asteroid’s impact, which contradicts some previous studies. The authors also suggest that if the impact did not occur, dinosaurs could continue to be the dominant group of terrestrial animals on the planet.
The study’s lead author, Joe Bonsor, received his doctorate jointly from the Milner Center for Evolution at the University of Bath and the Museum of Natural History.
He said: “Previous research by others has used various methods to conclude that dinosaurs would have died out anyway because they were in decline by the end of the Cretaceous.
“However, we show that if you expand the data set to include newer dinosaur family trees and a wider range of dinosaur species, the results don’t really point to that conclusion – in fact, only about half of them do.”
It is difficult to estimate the diversity of dinosaurs due to gaps in fossil records. This may be due to factors such as bones that have been preserved as fossils, how accessible the fossils are in the rock so that they can be found, and where paleontologists are looking for them.
The researchers used statistical methods to overcome these bias in sampling by looking at the rate of species formation of dinosaur families, instead of simply counting the number of species belonging to the family.
Joe Bonsor said: “The main point of our paper is that it’s not as simple as looking at a few trees and making a decision – the big inevitable fossil biases and lack of data can often indicate a decline in species, but that may is a reflection of reality at the time.
“We may never understand the true pace of dinosaur development, because the only way to know for sure is to fill in the gaps in the record to get the best answer, and we just don’t think we’re still there.
“Our data do not currently show that they were in decline, in fact some groups such as hadrosaurs and keratops have thrived and there is no evidence to suggest that they would have disappeared 66 million years ago if they had not disappeared.”
While mammals existed during the asteroid’s impact, the extinction of the dinosaurs alone led to the release of niches, which allowed the mammals to fill them and later dominate the planet.
Reference: “Dinosaur diversification has not decreased before the K-Pg limit” by Joseph A. Bonsor, Paul M. Barrett, Thomas J. Raven and Natalie Cooper, November 18, 2020,, Open science of the Royal Society.
DOI: 10.1098 / rsos.201195
The research was funded by the trust and the Leverhulme Museum of Natural History.