Scientists made a revolutionary discovery by unearthing a “missing link” fossil of a small ichthyosaur that moved on land like a seal but spent its time swimming in the ocean as well. Ichthyosaurs were a hugely expanded reptile nation whose record had not included any of the earliest forms representing the transition from their land reptile ancestors to creatures fully adapted to life in the sea.
But scientists said on Wednesday they have unearthed in China the fossil of a small ichthyosaur, Cartorhynchus lenticarpus, with large, flexible flippers dating back 248 million years ago, belonging to the Triassic period and measuring roughly 1.5 feet.
They called it the long-sought missing link revealing the early evolution of ichthyosaurs, one of the dominant marine reptile groups during the age of dinosaurs. “We finally got this milestone and this first ichthyosaur,” said palaeontologist Da-yong Jiang of Peking University in Beijing, who co-led the study published in the journal Nature.
“Many creationists have tried to portray ichthyosaurs as being contrary to evolution,” said lead author Ryosuke Motani, a professor of earth and planetary sciences at the University of California Davis. “We knew based on their bone structure that they were reptiles, and that their ancestors lived on land at some time, but they were fully adapted to life in the water. So creationists would say, well, they couldn’t have evolved from those reptiles, because where’s the link?” Now the gap has been filled, he explained.
Most known ichthyosaurs have long, beak-like snouts, but the amphibious fossil shows a nose as short as that of land reptiles. Moreover 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 been trying to find out 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.
Based on its body shape and large flippers, Cartorhynchus probably wasn’t a fast swimmer, instead rooting around for bottom-dwelling creatures like shrimp in what was then a tropical archipelago, Motani speculated.