Newly found fossil of 250-mln-yr-old 'amphibious ichthyosaur' fills evolutionary gap

Researchers have recently found the first fossil of 250-million-years-old amphibious ichthyosaur in China that fills the gap in the fossil records, it has been reported.

The discovery by University of California, Davis would be the first to link the dolphin-like ichthyosaur to its terrestrial ancestors, filling a gap in the fossil record.

The fossil represents a missing stage in the evolution of ichthyosaurs, marine reptiles from the Age of Dinosaurs about 250 million years ago. Until now, there were no fossils marking their transition from land to sea.

The researchers discovered the fossil in China's Anhui Province. About 248 million years old, it was from the Triassic period and measures roughly 1.5 feet long.

Unlike ichthyosaurs fully adapted to life at sea, this one had unusually large, flexible flippers that likely allowed for seal-like movement on land. It had flexible wrists, which are essential for crawling on the ground. Most ichthyosaurs have long, beak-like snouts, but the amphibious fossil shows a nose as short as that of land reptiles.

Its body also contains thicker bones than previously-described ichthyosaurs. This animal lived about 4 million years after the worst mass extinction in Earth's history, 252 million years ago.

Scientists have wondered how long it took for animals and plants to recover after such destruction, particularly since the extinction was associated with global warming and this study's implications go beyond evolutionary theory, according to Professor Ryosuke Motani, UC Davis Department of Earth and Planetary Sciences.

The study is published in the journal Nature.