Researchers in New Zealand have found the oldest Nothosaurus fossil in the Southern Hemisphere, dating back 246 million years, providing new information about the early marine adaptations and migrations of these ancient reptiles. An international group of researchers discovered the oldest marine reptile fossil (notosaurus vertebrae) found in the Southern Hemisphere on New Zealand’s South Island. At the dawn of the age of dinosaurs, 246 million years ago, New Zealand was located on the south polar coast of a huge superocean known as the Panthalassa.
Reptiles first invaded the seas after a devastating mass extinction that devastated marine ecosystems and paved the way for the beginning of the age of dinosaurs about 252 million years ago. Evidence of this evolutionary milestone has been found in only a few places around the world: the Arctic island of Svalbard, northwestern North America, and southwestern China. Although represented by a single vertebra excavated from a rock in a riverbed at the foot of Mount Harper on New Zealand’s South Island, the discovery sheds new light on previously unknown information about the first marine reptiles in the Southern Hemisphere.
Sauropterygian dominance
Reptiles dominated the seas millions of years before dinosaurs dominated the land. The most diverse and geologically longest-surviving group were the sauropterygians, with an evolutionary history of more than 180 million years. The group included long-necked plesiosaurs that resembled the popular image of the Loch Ness Monster. Nothosaurs were distant ancestors of plesiosaurs. They could grow up to seven meters in length and swim with the help of four paddle-like limbs. Nothosaurs had flattened skulls with a network of thin, conical teeth used to catch fish and squid.
The New Zealand Notthosaurus was discovered during a geological survey in 1978, but its significance was not fully appreciated until paleontologists from Sweden, Norway, New Zealand, Australia and East Timor combined their expertise to study and analyze the vertebrae and other fossils.
“Notosaurus, found in New Zealand, is more than 40 million years older than the oldest previously known sauropterygian fossils found in the Southern Hemisphere. We show that these ancient marine reptiles lived in shallow coastal environments teeming with marine life in what was then the southern Arctic Circle,” he explains. The lead author of the study is Dr. from Uppsala University Evolution Museum. Benjamin Kier.
The oldest Notosaurus fossils are approximately 248 million years old and have been found throughout the ancient northern low-latitude belt extending from the far northeast to the northwestern edges of the Panthalassa superocean. The origin, distribution, and timing of notosaurs reaching these remote areas are still debated. Some theories suggest they either migrated along the arctic coasts, sailed through inland sea routes, or used currents to cross the Panthalassa superocean.
A new Notosaurus fossil found in New Zealand has overturned these long-standing hypotheses.
“Using a time-calibrated evolutionary model of the global distribution of sauropterygians, we show that notosaurs arose near the equator and then rapidly spread both north and south, while complex marine ecosystems survived the catastrophic mass extinction that left the Earth at the beginning of the age of dinosaurs.” ” says Kir.
“The beginning of the age of dinosaurs was characterized by extreme global warming that allowed these marine reptiles to thrive in the South Pole. It also suggests that ancient polar regions were a possible route for their earliest global migrations, similar to the epic trans-oceanic journeys whales make today.” “There is no doubt that there are many more fossilized remains of long-extinct sea monsters in New Zealand and elsewhere in the southern hemisphere,” says Keir.
Source: Port Altele
