Research explains why crocodiles have changed so little since the era of the dinosaurs

New research by scientists at the University of Bristol explains how a ‘stop-start’ pattern of evolution, controlled by environmental change, may explain why crocodiles have changed so little since the era of the dinosaurs.

Crocodiles today look a lot like those from the Jurassic period about 200 million years ago. There are also very few species alive today – only 25. Other animals such as lizards and birds have reached a variety of thousands of species in the same time or less.

Prehistory has also seen species of crocodiles we do not see today, including giants as large as dinosaurs, herbivores, fast runners, and snake-shaped creatures that lived in the sea.

In the new research, published today in the journal Natural Communication Biology, the scientists explain how crocodiles follow an evolutionary pattern called ‘punctuation equilibrium’.

The rate of evolution is generally slow, but sometimes they develop faster because the environment has changed. This new research in particular suggests that their evolution accelerates when the climate is warmer, and that their body size increases.

Chief author, dr. Max Stockdale, of the University of Bristol’s School of Geographical Sciences, said: “Our analysis used a machine learning algorithm to estimate evolutionary rates. Evolutionary rate is the amount of change that has occurred over a given time that we can work out. by comparing measurements of fossils and taking into account how old they are.

“For our study, we measured body size, which is important because it interacts with how fast animals grow, how much food they need, how large their populations are and how likely they are to become extinct.”

The findings show that the limited diversity of crocodiles and their apparent lack of evolution is due to a slow rate of evolution. It would seem that the crocodiles achieved a body plan that was very effective and versatile enough not to change to survive it.

This versatility may be one of the reasons why crocodiles survived the meteoric impact at the end of the Cretaceous in which the dinosaurs perished. Crocodiles generally thrive better in hot conditions because they cannot control their body temperature and require heat from the environment.

The climate during the era of dinosaurs was warmer than it is today, and this may explain why there were many more species of crocodile than we see now. Being able to draw energy from the sun means that they do not have to eat as much as a warm-blooded animal such as a bird or mammal.

Dr Stockdale added: “It’s fascinating to see how a complex relationship exists between the earth and the living things we share it with. The crocodiles got a lifestyle that was versatile enough to adapt to the enormous “Environmental changes that have taken place since then. The dinosaurs were there.”

The next step for the team’s research is to find out why some species of prehistoric crocodile became extinct, while others did not.