Strange sea-dwelling reptile fossil hints at rapid evolution after mass extinction

 Date: May 23, 2016

Source: Field Museum

For a long time, scientists believed that the early marine reptiles that came about after the great Permian-Triassic mass extinction evolved slowly, but the recent discovery of a strange new fossil brings that view into question. The newly described Sclerocormus parviceps is a marine reptile called an ichthyosauriform, and its strange features (short snout, long, whip-like tail) are really different from many of its relatives, revealing that marine reptiles evolved and diversified after the extinction more quickly than previously thought.

Two hundred and fifty million years ago, life on earth was in a tail-spin--climate change, volcanic eruptions, and rising sea levels contributed to a mass extinction that makes the death of the dinosaurs look like child's play. Marine life got hit hardest--96% of all marine species went extinct. For a long time, scientists believed that the early marine reptiles that came about after the mass extinction evolved slowly, but the recent discovery of a strange new fossil brings that view into question.

In a paper published in Scientific Reports, paleontologists describe a new marine reptile, Sclerocormus parviceps, an ichthyosauriform that's breaking all the rules about what ichthyosaurs are like.

Ichthyosaurs were a massive group of marine reptiles that lived around the time of the earliest dinosaurs. Most of them looked a little bit like today's dolphins--streamlined bodies, long beak-like snouts, and powerful tail fins. But the new species is something of a black sheep. It has a short snout (its species name even means "small skull"), and instead of a tail with triangular flukes (think of a fish's tail-fins), it had a long, whip-like tail without big fins at the end. And while many ichthyosaurs had conical teeth for catching prey, Sclerocormus was toothless and instead seems to have used its short snout to create pressure and suck up food like a syringe. In short, it's really different from most of its relatives, and that tells scientists something important about evolution.

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