The 246-million-year-old specimen is the geologically oldest marine reptile to inhabit the Southern Hemisphere.
This image shows a nothosaurus swimming along the ancient Antarctic coast of what is now New Zealand about 246 million years ago (during the Triassic Period). Image courtesy of Stavros Kundromichalis.
“Reptiles dominated the seas millions of years before dinosaurs dominated the land,” said Dr Benjamin Kear from the Museum of Evolution at Uppsala University and his colleagues.
“The most diverse and geologically longest-surviving group are the sauropods, with an evolutionary history spanning more than 180 million years.”
“This group included the long-necked plesiosaurs. Nothosaurus was their distant ancestor.”
“Nothosaurus could grow up to 7 metres (23 feet) in length and swam using four paddle-like limbs. It had a flattened skull with a web of narrow, conical teeth that it used to catch fish and squid.”
The 246-million-year-old Nothosaurus fossil was discovered in 1978 in rocks found along a major tributary of the Balmacaan River at the foot of Mount Harper in the Harper Ranges of New Zealand's central South Island.
“The New Zealand nothosaurus is more than 40 million years older than the oldest sauropod fossil yet found in the Southern Hemisphere,” said Dr Keir, lead author of the paper. paper Published in the journal Current Biology.
“We show that these ancient marine reptiles lived in shallow coastal environments rich in marine life within the Antarctic Circle at that time.”
“The oldest nothosaurus fossils date back to about 248 million years ago and were found along an ancient low-northern latitude belt that stretched from the remote northeastern to northwestern edges of the Panthalassa superocean.”
“The origin, distribution and timing of the arrival of nothosaurs in these remote areas remain a matter of debate.”
“Some theories suggest that they migrated along Arctic coastlines, swam through inland seas, or used ocean currents to cross the Panthalassa superocean.”
Morphology and biogeographical context of the earliest sauropod-finned fish in the Southern Hemisphere. Image courtesy of Kear others., doi: 10.1016/j.cub.2024.03.035.
New fossils discovered in New Zealand overturn these long-held assumptions.
“Using a time-calibrated evolutionary model of the global distribution of sauropods, we show that nothosaurs originated near the equator and then rapidly spread north and south at the same time that complex marine ecosystems were being re-established after the great extinction that marked the beginning of the Age of Dinosaurs,” Dr Kear said.
“The beginning of the age of the dinosaurs was marked by extreme global warming, which allowed these marine reptiles to thrive in Antarctica.”
“This also suggests that the ancient polar regions were likely routes for their earliest global migration, similar to the epic transoceanic journeys undertaken by modern whales.”
“There are surely fossils of long-extinct sea monsters still waiting to be discovered in New Zealand and other parts of the Southern Hemisphere.”
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Benjamin P. Kear others2024. Earliest southern sauropods reveal early globalization of marine reptiles. Current Biology 34(12):562-563; doi: 10.1016/j.cub.2024.03.035
Source: www.sci.news
