They first appeared in the Late Cretaceous period, approximately 85 million years ago, and the 250 million year fossil record of their extinct relatives shows a diverse evolutionary history.

Extinct crocodilians and their relatives came in all shapes and sizes, including giant land-based creatures such as Sarcosuchus, which reached around 12 metres in length and weighed up to eight metric tonnes.

Crocodilians also roamed the ocean - for example, thalattosuchians were equipped with flippers and shark-like tails to make them more agile in the sea.

Researchers from Imperial College London, the University of Oxford, the Smithsonian Institution and the University of Birmingham compiled a data-set of the entire known fossil record of crocodilians and their extinct relatives and analyzed data about Earth's ancient climate.

Crocodilians are ectotherms, meaning they rely on external heat sources from the environment such as the Sun.

The researchers conclude that at higher latitudes in areas we now know as Europe and America, declining temperatures had a major impact on crocodilians and their relatives.

At lower latitudes the decline of crocodilians was caused by areas on many continents becoming increasingly arid.

The team found that fluctuations in sea levels exerted the main control over the diversity of marine species of crocodilians.

In the future, the team suggest that a warming world caused by global climate change may favor crocodilian diversification again, but human activity will continue to have a major impact on their habitats.

The study was published in the journal Nature Communications.

Latest News from Lifestyle News Desk