Tuesday, 23 October, 2018

Antarctic Fossils Rewrite Origin of Land Animals

Two newly discovered early amphibians Tutusius and Umzantsia that lived about 360 million years ago during the Devonian Period in South Africa. — Handout via Reuters Not so fishy: Africa's first ever fish-with-legs discovered
Sandy Nunez | 12 June, 2018, 03:26

Fossils of two amphibians that lived within the Antarctic circle 360 million years ago are forcing scientists to rethink the origins of land vertebrates, including where these pioneers first appeared and the climatic conditions that spawned them.

It's worth noting that the first ever tetrapods actually evolved from fish during the Devonian period.

The evolution of tetrapods - four legged vertebrates- from fishes was a key event in human ancestry and for a long time scientists have assumed that they had originated in Laurasia - the smaller supercontinent which included modern day North America, Greenland and Europe.

Although none of the fossils is complete, Gess explains in the video below that they were both easily recognizable as tetrapod remains.

They were among the early wave of tetrapods, a group including all land-living vertebrates. It is noted that the area in which were found the fossils was at the Antarctic polar circle.

Kubayi-Ngubane, meanwhile, said South Africa was richly endowed with natural resources, and the country's fossil wealth dated back more than three-billion years. In fact, one of the species was identified exclusively from a shoulder girdle bone. The species was estimated to be about 3 feet long.

According to Dr Gess, these tetrapods had evolved for survival in shallow waters thus they retained the fish-like tail but developed legs for use on land.

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"Work on South African paleosciences is of crucial national and worldwide importance, because it provides proof of our shared human origins, which are the mutual roots that bind all people within a common humanity", she said.

The much larger southern supercontinent, Gondwana, which incorporated present-day Africa, South America, Australia, Antarctica, and India, has hitherto yielded nearly no Devonian tetrapods, with only an isolated jaw (named Metaxygnathus) and footprints, being found in eastern Australia.

These Umzantsia usually measured around the twenty-eight inches in length, and it has featured a narrow lower jawline which has tiny pointed teeth. It was thought that in Laurissa, in the paleotropics, tetrapods evolved because that's where their fossils were found. This was found in Eastern Australia which was on the extreme northern tropical coast of Gondwana.

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

"It also implies that tetrapods could have originated anywhere, and that the next step, the move onto land, could also have occurred anywhere".

Robert Gess, a paleontologist at the Albany Museum in Grahamstown, said in a statement, "So we now know that tetrapods, by the end of the Devonian, lived all over the world, from the tropics to the Antarctic Circle".

At the same time, "Umzantsia" refers to the southern region where the species was found and "amazana" means "water ripples", pointing to the "very distinctive ornaments on the bone", says the paleontologist.