Polar marine reptile fossil is oldest in southern hemisphere

June 17 () –

An international team of scientists has identified the oldest fossil of a marine reptile in the southern hemisphere: a notosaur vertebra found on the South Island of New Zealand.

246 million years ago, at the beginning of the Age of Dinosaurs, New Zealand was located on the southern polar coast of a vast superocean called Panthalassa.

Reptiles invaded the seas for the first time after a catastrophic mass extinction that devastated marine ecosystems and paved the way for the dawn of the Age of Dinosaurs. almost 252 million years ago.

Evidence of this evolutionary milestone has only been discovered in a few places around the world: on the Arctic island of Spitsbergen, northwestern North America, and southwestern China. Although represented by a single vertebra that was excavated from a rock in a stream bed at the foot of Mount Harper on New Zealand’s South Island, this discovery has shed new light on the previously unknown record of the hemisphere’s first marine reptiles. south.

Reptiles ruled the seas for millions of years before dinosaurs ruled the land. The most diverse and geologically oldest group to survive was the sauropterygians, with an evolutionary history spanning more than 180 million years. The group included the long-necked plesiosaurs, which resembled the popular image of the Loch Ness monster. Notosaurs were distant predecessors of plesiosaurs. They could grow up to seven meters long and swam using four paddle-like limbs. Notosaurs had flattened skulls with a network of thin conical teeth that they used to catch fish and squid.

The New Zealand notosaur was discovered during a geological survey in 1978but its importance was not fully recognized until paleontologists from Sweden, Norway, New Zealand, Australia and East Timor pooled their knowledge to examine and analyze the vertebra and other associated fossils.

“The notosaurus found in New Zealand is more than 40 million years older than previously known sauropterygium fossils from the Southern Hemisphere. “We have shown that these ancient marine reptiles lived in a shallow coastal environment teeming with marine creatures within what then it was the southern polar circle,” he explains it’s a statement Dr. Benjamin Kear of the Museum of Evolution at Uppsala University, lead author of the study.

The oldest notosaurus fossils They are around 248 million years old and have been found along an ancient belt of low northern latitudes that extended from the remote northeastern to northwest margins of the Panthalassa superocean. The origin, distribution, and timing of notosaurs arriving in these distant areas are still debated. Some theories suggest that they either migrated along the northern polar coasts, swam through inland sea lanes, or used currents to cross the Panthalassa superocean.

The new notosaur fossil from New Zealand has turned these old hypotheses upside down.

“Using a time-calibrated evolutionary model of global sauropterygian distributions, we show that notosaurs originated near the equator and They then spread rapidly both north and south while reestablishing complex marine ecosystems after the cataclysmic mass extinction that ushered in the Age of Dinosaurs,” says Kear.

“The beginning of the Age of Dinosaurs was characterized by extreme global warming, which allowed these marine reptiles to thrive at the South Pole. This also suggests that the ancient polar regions were a likely route for their first global migrations, very similar to the epic transoceanic voyages that whales undertake today. “There are undoubtedly more fossil remains of long-extinct sea monsters waiting to be discovered in New Zealand and elsewhere in the southern hemisphere,” says Kear.