Fossil pre-dating dinosaurs confirms nothosaurs existed in Southern Hemisphere

A 246-million-year-old fossil discovered in Canterbury upends long-standing theories about Earth's natural history, researchers say.

Scientists from New Zealand working alongside researchers from Sweden, Norway, Australia and Timor-Leste found the fossilised vertebra belonged to the nothosaur, a reptile resembling the Loch Ness monster that lived before dinosaurs.

GNS Science held onto the fossil after palaeontologist Dr Hamish Campbell discovered it in 1978, but it was not properly studied until this year.

Campbell said he was "absolutely delighted" to learn the fossil's full history more than 30 years after finding it in the Balmacaan Stream in Canterbury.

"I was blissfully unaware that this fossil had come to the attention of the right people: vertebrate palaeontologists who know their stuff. I'm thrilled," he said.

He said the fossil was the oldest of its kind.

"We [now] know the age of this fossil, and it's a lot older than the oldest known similar fossil from the Southern Hemisphere," Dr Campbell said.

"Previously, fossils had been found in New Zealand that had tantalisingly been tentatively identified as possible nothosaurs, but this fossil really clinches it."

He said scientists were previously unsure if nothosaurs lived in the Southern Hemisphere.

"An awful lot of what we as humanity know about this group of organisms is based on fossils from the Northern Hemisphere," he said.

"Here we are, little old New Zealand way down at the bottom of the other end of the world, and we have this fantastic record of early Triassic time."

Nothosaurs were predecessors to plesiosaurs, massive swimming lizards with long necks and flippers.

"It's a sauropterygian, so to translate that it means 'lizard flipper,' a marine reptile," Dr Campbell said.

"They had long necks and relatively small elongated flattened heads with lots of sharp teeth. The teeth projected outwards, perfect for catching fish and squid. They had a long tail and were probably extremely fast moving."

The fossil predated the oldest known dinosaurs and mammals by millions of years, he said.

"They flourished after the big extinction at the end of Permian time. Something really dramatic happened to this planet 251.9 million years ago which marked the onset of Triassic time," he said.

"New Zealand looked very, very different in Triassic time, we were just part of the edge of Southern Gondwana, and we were very close to the pole. This fossil was found in sediments that would have accumulated in relatively deep water off the coast of Gondwana."

The study found that nothosaurs lived in a shallow coastal environment within the southern polar circle, now inland Canterbury.

"There's potential to find more fossils in New Zealand because we have lots of rocks of this age," Dr Campbell said.

"It will mean that New Zealand will become, yet again, of great interest to the international science fraternity."