New analysis shows dinosaurs would have continued to rule Earth if the asteroid hadn’t hit

A new statistical analysis of dinosaur diversity shows that they were not in decline when they were extinct by an asteroid that hit 66 million years ago.

Researchers at the University of Bath and the Natural History Museum in London say that if the impact had not happened, dinosaurs would have continued to dominate Earth.

Dinosaurs were widely distributed around the world at the time of the asteroid impact at the end of the end of the Cretaceous period, occupying all continents of the planet and were the dominant animal form of most terrestrial ecosystems.

However, it is still controversial among paleobiologists whether dinosaurs were declining in diversity at the time of their extinction.

Statistical modeling

In order to answer this question, the research team assembled a set of different dinosaur family trees and used statistical modeling to assess whether each of the major dinosaur groups was still capable of producing new species at this time.

Their study, published in the journal Royal Society Open Science, found that dinosaurs were not in decline before the asteroid struck, contradicting some previous studies. The authors also suggest that had the impact not taken place, dinosaurs might have continued to be the dominant group of land animals on the planet.

Lead author of the study, Joe Bonsor, is undertaking his PhD jointly at the Milner Center for Evolution at the University of Bath and the Natural History Museum.

He said: “Previous studies done by others have used various methods to draw the conclusion that dinosaurs would have died anyway, as they were in decline around the end of the Cretaceous.

“However, we show that if you expand the dataset to include more recent dinosaur family trees and a larger set of dinosaur types, not all of the results lead to this conclusion – in fact, only half of ‘between them do.

Sampling bias

It is difficult to assess the diversity of dinosaurs due to gaps in the fossil record. This may be due to factors such as which bones are kept as fossils, the accessibility of fossils in rock to allow them to be found, and where paleontologists look for them.

The researchers used statistical methods to overcome these sampling biases, by examining the speciation rates of dinosaur families rather than simply counting the number of species in the family.

Joe Bonsor said: “The main point of our article is that it’s not as simple as looking at a few trees and making a decision – The inevitable large biases in the fossil record and lack of data can often show a decline cash, but that may not reflect the reality of the time.

“We may never know the true rates of evolution of dinosaurs, because the only way to find out is to fill in the gaps in the file to get the best answer, and we just don’t think we’re there yet.” .

“Our data does not currently show that they were in decline, in fact some groups such as hadrosaurs and ceratopsians were in full swing and there is no evidence to suggest that they would have become extinct 66 million years ago. if the extinction event had not occurred.

While mammals existed at the time of the asteroid strike, it was only thanks to the extinction of the dinosaurs that led to the evacuation of the niches, allowing mammals to fill them and later dominate the planet.

Reference: “Dinosaur diversification rates were not declining before the K-Pg limit” by Joseph A. Bonsor, Paul M. Barrett, Thomas J. Raven and Natalie Cooper, November 18, 2020, Royal Society Open Science.
DOI: 10.1098 / rsos.201195

The research was funded by the Leverhulme Trust and the Natural History Museum.