Stavros Kundromichalis
An artist’s reconstruction of the oldest known marine reptile from the Southern Hemisphere: a nothosaur swimming along the ancient south polar coast of present-day New Zealand some 246 million years ago.
CNN
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Scientists have discovered a 246-million-year-old marine reptile fossil, the oldest of its kind in the Southern Hemisphere, which sheds new light on the early evolution of marine mammals.
The largest mass extinction in the fossil record—known as the “Great Dying”—occurred about 252 million years ago and wiped out about 95% of species on land and in the sea.
This was followed by the appearance of new creatures that evolved from the survivors, including reptiles that evolved from living on land to living in the sea.
Sauropterygs were ancient aquatic reptiles that existed for approximately 180 million years during the Mesozoic Era, 251 to 66 million years ago.
Nothosaurs were a type of sauropterygian that lived on Earth during the Triassic period, the first period of the age of dinosaurs, between 251 million and 200 million years ago.
However, their early development was known only from fossils found in the northern hemisphere, according to a study published in the journal Current Biology Monday.
Fossils of these animals have been 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 study lead author Benjamin Kear, a paleontologist at Uppsala University. Museum of Evolution in Sweden.
“But it’s totally unexpected to find someone on the other side of the Earth,” Kear told CNN on Tuesday.
At the time of the nothosaurs, almost all of the land masses were incorporated into a single supercontinent known as Pangea. This supercontinent was shaped like a horseshoe, and in the middle was the Paleo-Tethys Ocean, where Kear thought these animals lived.
He said the big question was how these animals got from one side of the Earth to the other because the other side was surrounded by a giant global ocean called Panthalassa that stretched from pole to pole.
“It’s never been explained, we don’t know what’s going on. “All of a sudden we find a nothosaurus at the South Pole in New Zealand, so it kind of turns everything upside down,” Kear said.
According to a university press release, a single nothosaur vertebra was found in 1978 along the Balmacaan Stream at the foot of Mount Harper in New Zealand. Many fossils are being found all the time and the material has been deposited in New Zealand’s National Paleontology Collection, Kear said. The discovery was brought to his attention by the late paleontologist Robert Ewan Fordyce, but the coronavirus pandemic delayed researchers who set out to see it until last year.
Only after an international team of paleontologists examined the vertebra and fossils from the rocks surrounding it did they discover that it pushed back the sauropterygian fossil record in the Southern Hemisphere by more than 40 million years.
Kear 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 the dinosaurs, they basically adapted to life in the sea and … suddenly went global. ”
The researchers said the fossil provides the first evidence that early globalization was happening at the same time that these reptiles were on the rise, as oceanic predators and complex marine ecosystems were forming.
The study suggests that these ancient marine reptiles skirted the Earth’s poles, swimming all the way around the supercontinent as a continuous coastal highway, Kear said.
Nothosaurs had a slender body, long neck, long limbs and tail. They would paddle through the water with their limbs. But later sauropterygians developed better paddles.
Kear, who also works in Svalbard in the Norwegian Arctic, said scientists plan to look for more fossils around the world in an effort to “follow these stories from pole to pole” and understand how animals migrated around the supercontinent.
“What we’re looking at here is probably a story that goes beyond this superextinction event, goes deeper in time, and we can start to see that these animals were already adapting to life in the sea,” he said. “We’ll see, we’ll keep digging and see what we find.”