An ancient reptile fossil sheds new light on early marine evolution

CNN
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Scientists have discovered a 246-million-year-old marine reptile fossil, the oldest of its kind ever found in the Southern Hemisphere, shedding new light on the early evolution of marine mammals.

the The greatest mass extinction event In the fossil record – known as the “Great Dying” – it occurred about 252 million years ago, wiping out about 95% of species that lived on land and sea.

What followed was the emergence of new creatures that evolved from those that survived, including reptiles that evolved from living on land to living in the sea.

Sauropterygians were ancient aquatic reptiles that existed about 180 million years ago during the Mesozoic Era, 251 to 66 million years ago.

Notosaurs were a type of sauropterygian that lived on Earth during the Triassic Period, the first period of the Age of Dinosaurs, 251 million to 200 million years ago.

However, its early evolution was only known from fossils found in the Northern Hemisphere, according to the study published in the journal. Current biology Monday.

Fossils of these animals are commonly found in Europe, as well as southwestern China and the Middle East, with some fragmentary occurrences in Wyoming in the United States and British Columbia in Canada, according to lead study author Benjamin Kerr, a paleontologist at Uppsala University. Evolution Museum in Sweden.

“But it’s not at all expected to find one at the other end of the Earth,” Kerr told CNN on Tuesday.

At the time when notosaurs existed, almost all of Earth’s land masses were combined into one giant continent known as Pangea. This giant continent was shaped like a horseshoe, and in its center was the Paleo-Tethys Ocean, where these animals are believed to have lived, according to Kerr.

He said the big question is how these animals moved from one side of the Earth to the other, since the other side was surrounded by a giant global ocean called Panthalassa, which extends from pole to pole.

“This has never been explained, and we don’t know what’s going on. All of a sudden, we find a Notosaurus in the Antarctic in New Zealand, so it’s like it’s turned everything upside down,” Kerr said.

A single nothosaur vertebra was found in a more rugged area along the Balmacaan River at the base of Mount Harper in New Zealand in 1978, according to a university press release. Many fossils are found all the time, Kerr said, and the material has been deposited in New Zealand’s National Fossil Collection. The late paleontologist Robert Euan Fordyce alerted him to the discovery, but the coronavirus pandemic delayed researchers traveling to look at it until last year.

Only after an international team of paleontologists examined the vertebra and fossils from the surrounding rocks did they discover that it pushed back the fossil record of sauroptera in the Southern Hemisphere by more than 40 million years.

Kerr said the age of the fossil is “really interesting” because it shows that “246 million years ago, which is very close to the dawn of the age of dinosaurs, they basically adapted to life in the sea and…suddenly became cosmopolitan.” ”

The fossil provides the first evidence that early globalization was occurring at the same time these reptiles were rising as oceanic predators and complex marine ecosystems formed, the researchers said.

Kerr said the study suggests that these ancient marine reptiles roamed around Earth’s poles, swimming all the way around the supercontinent like a continuous coastal highway.

Nothosaurs had a slender body, long neck, long limbs, and tail. They were paddling in the water with their limbs. But over time, later sauropterygians developed better paddles.

Kerr, who also works on Svalbard in the Norwegian Arctic, said researchers plan to search for more fossils around the world in an attempt to “trace these stories from pole to pole” and understand how animals migrated around the supercontinent.

“What we’re looking at here may be a story that goes beyond this super-extinction event, and goes further back in time, and we can start to see that these animals were actually adapted to life in the sea,” he said. “We’ll see. We’ll keep digging and see what we can find.”