The oldest ichthyosaur suggests a mysterious origin

The oldest ichthyosaur fossils ever found (250 million years ago) suggest that this fish-like reptile evolved earlier than thought, perhaps even before the worst mass extinction on Earth (252 million years ago). The paper was published March 13 in Current Biology.

An early ichthyosaur discovered on Spitsbergen Island. Photo by Esther van Hulsen

Ichthyosaurus was one of the reptiles that rapidly multiplied along with dinosaurs after the mass extinction at the end of the Permian. Scientists believe they evolved from their terrestrial ancestors after the mass extinction.

The fossils, found on the Norwegian island of Spitsbergen, include 11 vertebrae and 15 bone fragments. Researchers such as Benjamin Kear of Uppsala University in Sweden believe they belong to the fish-finned dragon family, an eel-like reptile that lives in water and is the ancestor of the shark-shaped ichthyosaur.

The team performed a series of analyses ranging from petrochemistry to microscopic bone structure. “These vertebrae came from a highly evolved, fast-growing, possibly warm-blooded and completely oceanic ichthyosaur,” Kear said. ”

The fossils found are wrapped in a rock formation dating back about 2 million years after the mass extinction at the end of the Permian, making them the earliest known ichthyosaur fossils to date. The fact that the animal from Spitsbergen was aquatic suggests that the ancestors of the earliest amphibian ichthyosaurs must have been much older, Klear said.

This suggests that these animals originated before the mass extinction, although more fossils are needed to confirm whether fish-finned dragons actually swam in the sea before the mass extinction.

Neil Kelley of Vanderbilt University in Nashville, Tennessee, who was not involved in the study, believes that the idea that ichthyosaur ancestors evolved in the Permian is plausible, but it is also possible that this group evolved rapidly as life resumed 2 million years after the mass extinction. For example, previous studies of Triassic giant ichthyosaurs have shown that these reptiles thrived in staggering proportions over about 2.5 million years.

Until we find fossils of some Permian ichthyosaurs or their close relatives, it’s hard to say when these aquatic reptiles began to thrive rapidly, Kelley said. (Source: China Science News, Wang Jianzhuo)

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