Fossil Provides Clues to extinction 250 million years ago

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Scientists have found clues from a newly-classified fossil as to how life in the oceans recovered from a mass extinction about 250 million years ago.

Two hundred and fifty million years ago, climate change, volcanic eruptions, and rising sea levels contributed to a mass extinction that hit the marine life the hardest, with 96% of all marine species going extinct.

For a long time, scientists believed that the early marine reptiles that came about after the mass extinction evolved slowly. However, the newly discovered fossil brings into question their theory.

The newly classified specimen suggests that marine reptiles evolved quickly after the event.

Marine Reptile Suggests Quick Evolution

The reptile is an early relative of the ichthyosaurs, which were a large group of marine reptiles that swam at the time the dinosaurs roamed the earth. They were common in the Jurassic and the Cretaceous periods.

Prof Ryosuke Motani of the department of earth science at UC Davis, who worked on the fossil, said

Sclerocormus is one of the most surprising marine reptiles that I have seen,” he explained.

“Measuring 1.6 metres in total length it was one of the largest marine vertebrates of the time.

“It appeared after the mass extinction, which was at the end of the Permian, and quickly became extinct.”

Details of the specimen, Sclerocormus parviceps, are discussed in Scientific Reports.

Dr. Nick Fraser said,

“Here’s something that gives us a sense of the evolutionary pathway,” said Dr Fraser.

“We’ve still got a long way to go to see where the ichthyosaurs came from, however it’s a step in the right direction.

“And it all points to a very rapid radiation after this mass extinction – this mother of all extinctions at the end of the Permian, which had a major impact on the Earth.”

Dr Nick Fraser is the Keeper of Natural Sciences at National Museums Scotland.

He worked on the analysis of the fossil alongside teams in the US and China.

The ichthyosaurs were a large group of marine reptiles that were dolphin like in shape with streamlined bodies and long snouts.

However, while many ichthyosaurs had teeth for catching prey, Sclerocormus lacked teeth and probably sucked up food.

“It looked a bit like a small-headed porpoise with a fairly broad stiff body,” Dr Fraser told BBC News.

The newly classified specimen fills the gap in the fossil record between primitive marine reptiles and ichthyosaurs, which dominated the oceans for millions of years.

“We don’t have many marine reptile fossils from this period, so this specimen is important because it suggests that there’s diversity that hasn’t been uncovered yet,” said co-researcher Dr Olivier Rieppel of The Field Museum in Chicago.

“These ichthyosauriforms (ichythyosaurs and close relatives) seem to have evolved very quickly, in short bursts of lots of change, in leaps and bounds.”