Illustration of early ichthyosaurs from Spitsbergen
Esther Van Halsen
The oldest fossils of ichthyosaurs ever found show that these fish-like reptiles evolved earlier than we thought. Perhaps even before the world’s worst mass extinction, which occurred 252 million years ago.
Ichthyosaurs were one of the reptile lineages that co-proliferated with the dinosaurs after the end-Permian mass extinction. It was thought to have evolved from a terrestrial ancestor after a mass extinction.
The new fossils are 11 vertebrae and 15 bone fragments found on the Norwegian island of Spitsbergen in the Arctic. Benjamin Kier and his colleagues at Uppsala University in Sweden believe they belong to the ichthyosaur family.
The team performed a series of analyzes ranging from rock chemistry to microscopic bone structure. “It turned out to be that of a highly developed, rapidly growing, probably warm-blooded, fully marine ichthyosaur,” he says.
The fossils are encased in rock formations some two million years after the end-Permian mass extinction, making them the oldest known ichthyosaur fossils.
The fact that the animals of Spitsbergen were already aquatic suggests that the ancestors of the first amphibious ichthyosaurs must be even older, says Kear.
This suggests that these animals arose before the mass extinction, but many more are needed to confirm whether ichthyosaurs really swam in the ocean before the ecological disaster struck. fossil is required.
Neil Kelly of Vanderbilt University in Nashville, Tennessee, said that while the idea that the ancestors of ichthyosaurs evolved in the Permian period is reasonable, it’s also possible that the group evolved rapidly over the next two million years. says there is. A mass extinction in which life is restored. For example, previous studies of giant Triassic ichthyosaurs show that these reptiles swelled to gigantic proportions within about 2.5 million years.
Until Permian fossils of ichthyosaurs or their close ancestors are found, it will be difficult to determine when these aquatic reptiles plummeted, says Kelley.
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