Monday 14 March 2016

What killed off the ichthyosaurs? This study has the answer.

MARCH 9, 2016

by John Hopton

Ichthyosaurs were like an awesome cross of dinosaurs and dolphins-- could there be anything cooler? All good things must come to an end, and cool as they were, ichthyosaurs (yeah, we know they're not technically dinosaurs) had to die out eventually. Scientists think they just discovered exactly how that happened.

The dolphin-like marine reptiles likely became extinct 94 million years ago due to the combination of global warming and their inability to evolve quickly enough, Reuters reports

Around that time, Earth was approaching its hottest period of the past 250 million years, leading to strong fluctuations in sea levels and temperatures that left huge sections of seafloor without the oxygen necessary for air-breathing ichthyosaurs to live. These shifts prompted changes to ichthyosaur migratory routes, food availability, and birthing grounds.

A rapid demise 
The research challenges an older hypothesis that the animals were victims of competition with emerging predators such as the ocean-going lizards, mosasaurs. The new study shows that ichthyosaurs went extinct before mosasaurs even appeared.

This study suggests ichthyosaurs' demise happened much more rapidly than the previously posited decline over tens of millions of years.

"We find that the extinction was abrupt, not gradual," said University of Oxford paleontologist Roger Benson.

The researchers examined the ichthyosaur fossil record in order to reconstruct the group's evolutionary diversity, at the same time scrutinizing evidence of climate change that coincided with their extinction.

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