Ancient oceans, however, were full of marine reptiles and there were hundreds of crocodile species. Over the past 200 million years, there were four separate occasions when crocodiles entered (or re-entered) the sea, and each time they eventually went extinct. New research reveals that these ancestors of today’s crocodiles colonized the oceans during warming phases and went extinct during cold phases.
“We thought each of these evolutionary events might have had a different cause,” lead author Dr. Jeremy Martin of the Université de Lyon in France explained in a news release. “However, there seems to be a common pattern.”
Dr. Martin and a team of paleontologists and geochemists compared the evolution of marine crocodilian fossil species to a previously established sea temperature curve over the last 200 years. They found that the colonization of the oceans about 180 million years ago coincides with a period of global warming and the subsequent extinction, some 25 million years later, matches a period of global freezing.
This happened three more times, showing that the evolution of marine crocodilians is closely tied to temperature or their habitat.
“This work illustrates a case of the impact of climate change on the evolution of animal biodiversity, and shows that for crocodilians, warming phases of our earth’s history constitute ideal opportunities to colonize new environments,” said co-author Professor Michael Benton from the University of Bristol.
The report notes that one fossil lineage did not follow this trend; Jurrasic metriorhynchoids outlived the groups that went extinct by a few million years. This exception will likely lead to additional research in the future.
To learn more:
- Read the news release: Neither too hot nor too cold: the evolution of marine crocodilians constrained by ocean temperatures.
- See the full study: Sea surface temperature contributes to marine crocodylomorph evolution.
Copyright © 2014 by Marine Science Today, a publication of Marine Science Today LLC.