Artist's impression of Tutusius at Waterloo Farm by Maggie Newman
Artist's impression of Tutusius at Waterloo Farm by Maggie Newman

Scientists have discovered fossils from two new species of the world’s earliest land-walking vertebrates in the Eastern Cape — suggesting these ancient four-legged creatures did not just inhabit the warm waters of the tropics but lived in the Antarctic Circle too.

The research will force scientists to rethink tetrapod evolution, Robert Gess, a researcher at the Albany Museum in Grahamstown and lead author of a paper describing the find published in the peer review journal Science, said on Thursday.

Tetrapods were land pioneers that evolved from lobe-finned fishes during the Devonian period, which began 400-million years ago.

The new fossils are about 360-million years old and are the first tetrapods found in SA. The creatures lived in what was then the southernmost part of the super-continent Gondwanaland, which extended 70% south to within the Antarctic Circle and later broke up into several continents, including Africa.

Until now tetrapod fossils have been found only in locations that lay within 30 degrees north or south of the equator during the Devonian period. Most were discovered in what was once Laurussia, which broke into North America, Greenland and Europe.

The only tetrapod fossils found in what was previously Gondwanaland came from Australia, which lay on its northern edge in the tropics. Gondwanaland split into South America, Africa, India, Australia, the Arabian peninsula and Antarctica.

"What this tells us is that tetrapods lived all over the world, and there is no particular reason to think they arose in the tropics," said Gess.

"They are our ancestors and an incredibly important part of our evolutionary history. They are the link between fish and four-legged animals," he said in an interview on Thursday.

The two new species — Tutusis umlambo and the slightly smaller Umzantsia amazana — had a crocodile-like head, four stubby legs and a tail with a fish-like fin. Tutusis is named in honour of Archbishop Desmond Tutu, while Umzantsia reflects its South African heritage. Both were found in black shale at the Waterloo Farm roadcut, which was exposed during controlled explosions along the N2 highway between Grahamstown and the Fish River in 2016.

The site has yielded many other fossils that offer clues about the environment inhabited by the tetrapods, said Gess.

Gess’s research was funded by the University of the Witwatersrand’s Centre for Excellence in Palaeosciences and the Millennium Trust.