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African fossils rewrite origins of life

12 June 2018

The discovery of Tutusius umlambo and Umzantsia amazana in the coastal Eastern Cape province, near polar latitudes, suggests that four-limbed animals were more widespread in their early stages of evolution, contrary to widespread views that the ancestors of all vertebrates - the amphibious, aquatic tetrapods that first colonised the land - evolved in warm tropical environments.

At the time, Africa was part of the vast continent of Gondwana, made up of what are now South America, Australia, Antarctica, India and Madagascar.

Tutusius is represented by a single bone from the shoulder girdle‚ whereas Umzantsia is known from a greater number of bones‚ but they both appear similar to previously known Devonian tetrapods. The early tetrapods originated from the fishes at the time of the Devonian period.

Although the fossils are incomplete, alive these creatures would have resembled a cross between a crocodile and a fish, sporting a crocodile like head, stubby legs and a tail with a fish-like fin.

According to scientists, some amphibian fossils that they have recently unearthed and which lived near the Antarctic circle about 360-million-years ago might make them rethink what they previously believed about land vertebrates. The Tutusius reportedly named after Desmond Tutu, the Human Rights activist and South African Anglican cleric, measured near about one meter in length.

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

"Whereas all previously found Devonian tetrapods came from localities which were in tropical regions during the Devonian, these specimens lived within the Antarctic circle", highlighted Dr. Robert Gess, the lead author of the study. Scientists found them at the Waterloo Farm that is Grahamstown, South Africa.

The Farm locality is a roadcut that exposed dark grey mudstones rich with Devonian fossils of animals and plants.

The real importance of Tutusius and Umzantsia lies in where they were found.

Until now, it was widely accepted that creatures first stepped foot on land in a tropical supercontinent called Laurasia, which included modern-day North America, Greenland and Europe.

Scientists have found the fossils of Africa's oldest four-legged vertebrates, a unusual pair of Devonian tetrapods that lived within the Antarctic Circle. This was found in Eastern Australia which was on the extreme northern tropical coast of Gondwana. 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. But in the late Devonian-early Carboniferous period, the climate became more severe and occurred in the past.

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. There is probably not another country on the planet that so fully documents the long and dramatic evolutionary history of our own lineage.

African fossils rewrite origins of life