Fossil evidence has been uncovered that connects the dolphin-like ichthyosaur to an amphibious past, the first specimen to mark the creature's transition from land to sea and one that fills a gap in the fossil record.
The evidence comes thanks to researchers from the University of California, Davis, who have found the remains of an amphibious ichthyosaur in China's Anhui Province.
Ichthyosaurs were marine reptiles from the dinosaur age some 250 million years ago. Before this find, there was no fossil evidence of the time when they were moving toward life at sea.
"But now we have this fossil showing the transition," said the paper's lead author, Ryosuke Motani, a professor in the U.C. Davis department of earth and planetary sciences, in a press release. "There's nothing that prevents it from coming onto land."
The fossil has been dated to 248 million years ago, during the Triassic period (250 to 200 million years ago) and is about 1.5 feet long.
The new ichthyosaur fossil has marked differences from the ichthyosaurs science has already cataloged, the latter having adapted completely to living at sea. The new find had uncommonly large flippers that were flexible enough to allow the creature to move as though it were at sea while on land. Its wrists, meanwhile, were also flexible enough to enable crawling on land.
The amphibious ichthyosaur also had a short nose that was consistent with that of land reptiles and in contrast with the long, beak-like snouts of sea-dwellking ichthyosaurs.
The fossil also points to a creature with the thick-set bones usually associated with marine reptiles that were transitioning from land lubbing to sea life. Its bigger bones indicate the creature was growing heavier, the better to be able to plow through rough coastal waters before heading out to sea.
The U.C. Davis team has described the new fossil in the November 5 issue of the journal Nature.