Recently, the researchers found a 248 million year old fossil of an ancient reptile in China, which is believed to be the oldest known member of a well-known group of marine reptiles, and might have lived both on land and in the sea.
The researchers revealed that the specimen is an ancient type of ichthyopterygian, a group related to ichthyosaurs, which are large marine reptiles that dominated the world’s oceans after the Permian-Triassic extinction. At that time, approximately 252 million years ago, around 96% of marine animals and 70% of land animals went extinct. Researchers said, the recently discovered fossil provides new evidence that ichthyosaurs evolved from creatures that lived on land. The study is published in the Nature journal on 5th Nov.
The lead-author of the study and a geologist at Peking University in China, Da-yong Jiang said, “This new animal is a link between the terrestrial ancestor and the ichthyosaurs fully adapted to a life in the sea.”
Ichthyosaurs, which is a Greek name for “fish lizard,” lived from about 248 million to 95 million years ago. The group was extremely diverse, with body lengths ranging from less than 3.3 feet (1 meter) to more than 66 feet (20 m).
Jiang told Live Science in an email, “So far, all known ichthyosaur fossils came from animals that lived exclusively in the ocean, and there was a huge gap in the fossil record between them and their ancestors. Scientists didn’t know whether their ancestors were reptiles or amphibians, and if they lived on land or not.”
The recent specimen named “Cartorhynchus lenticarpus” discovered by Jiang and his team is the smallest known ichthyosaur-type creature — only about 1.3 feet (0.4 m) long. “We think the animal is fully grown, but cannot rule out the possibility that the fossil is the remains of an immature form of a larger creature,” researchers say.
In contrast to other ichthyosaurs, the new specimen has oddly large flippers that perhaps limited its ability to get around on land, making it similar to a modern seal. It also has a short muzzle and body trunk, like other land reptiles, the researchers said.
Jiang said, “The animal was probably a suction feeder on the seafloor, and may have eaten worms or eel-like creatures called conodonts. The fossil is quite complete and well-preserved; just part of the animal’s tail is missing.”
The fossil is discovered during an excavation in Chaohu, South China, in 2011. During the dig, researchers found several skeletons of ancient ichthyosaurs and extinct aquatic reptiles called sauropterygians, as well as fishes and other creatures.
Sine 2002, Jiang and his colleagues have been doing excavations in South China, looking for the first ichthyosaur that “jumped into the sea,” he said, so the new discovery “is a milestone after our hard work for more than 10 years.”
