The ichthyosaur, whose discovery was announced Wednesday, fills a crucial gap in the evolution of these dolphin-like predators, which thrived in Jurassic seas about 200 million to 145 million years ago. The reptiles could grow to 65 feet (20 meters) in length, about as long as a tractor-trailer.
Scientists knew that ichthyosaurs evolved from land to the sea, since they have found fossils of both land-dwelling ancestors and the fast-swimming marine creatures—sometimes nicknamed “sea monsters.”
So paleontologists suspected there must be some in-between ichthyosaurs out there. For instance, both whales and plesiosaurs, another type of ancient marine reptile, made the move from land to sea, and scientists have unearthed fossils of amphibious species that show that transition.
Recently, scientists excavating a site in Anhui Province (map) found the specimen they’d long sought: a fossil from a 1.5-foot-long (0.5 meter) animal that lived 248 million years ago, during the early Triassic period.
With a short snout, heavy build, and unusually large flippers, the newfound Cartorhynchus lenticarpus was built for both land and sea, researchers report in the journal Nature.
“An amphibious animal was somehow missing from the ichthyosaur record, and this animal fits that picture very nicely,” said study leader Ryosuke Motani of the University of California, Davis, an expert on prehistoric marine reptiles.
The newly discovered species may have evaded paleontologists simply because people haven’t dug into enough early Triassic deposits, speculated Motani, whose work was funded by the National Geographic Society’s Committee for Research and Exploration.
In fact, Motani wasn’t sure what he had at first: “When I first saw the animal, I was really puzzled.”
Eventually, Motani and colleagues pieced together a bottom dweller with unique adaptations for amphibious life.