[ad_1]
The 246-million-year-old specimen represents the geologically oldest sea-going reptile from the southern hemisphere.
This image shows nothosaurs swimming along the ancient southern polar coast of what is now New Zealand around 246 million years ago (Triassic period). Image credit: Stavros Kundromichalis.
“Reptiles ruled the seas for 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 was the sauropterygians, with an evolutionary history spanning over 180 million years.”
“The group included the long-necked plesiosaurs. Nothosaurs were their distant predecessors.”
“Nothosaurs could grow up to 7 m (23 feet) long and swam using four paddle-like limbs. They had flattened skulls with a meshwork of slender conical teeth that were used to catch fish and squid.”
The 246-million-year-old nothosaur fossil was recovered in 1978 from a loose boulder found along the main tributary of Balmacaan Stream at the base of Mt Harper in the Harper Range on central South Island, New Zealand.
“The nothosaur found in New Zealand is over 40 million years older than the previously oldest known sauropterygian fossils from the southern hemisphere,” said Dr. Kear, lead author of a paper published in the journal Current Biology.
“We show that these ancient sea reptiles lived in a shallow coastal environment teeming with marine creatures within what was then the southern polar circle.”
“The oldest nothosaur fossils are around 248 million years old and have been found along an ancient northern low-latitude belt that stretched from the remote northeastern to northwestern margins of the Panthalassa super-ocean.”
“The origin, distribution and timing of when nothosaurs reached these distant areas are still debated.”
“Some theories suggest that they either migrated along northern polar coastlines, or swam through inland seaways, or used currents to cross the Panthalassa super-ocean.”
Morphology and biogeographic context of the oldest southern hemisphere sauropterygian. Image credit: Kear et al., doi: 10.1016/j.cub.2024.03.035.
The new fossil from New Zealand upends these long-standing hypotheses.
“Using a time-calibrated evolutionary model of sauropterygian global distributions, we show that nothosaurs originated near the equator, then rapidly spread both northwards and southwards at the same time as complex marine ecosystems became re-established after the cataclysmic mass extinction that marked the beginning of the age of dinosaurs,” Dr. Kear said.
“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 earliest global migrations, much like the epic trans-oceanic journeys undertaken by whales today.”
“Undoubtedly, there are more fossil remains of long-extinct sea monsters waiting to be discovered in New Zealand and elsewhere in the southern hemisphere.”
_____
Benjamin P. Kear et al. 2024. Oldest southern sauropterygian reveals early marine reptile globalization. Current Biology 34 (12): 562-563; doi: 10.1016/j.cub.2024.03.035
