The first African fossils of Devonian tetrapods (four-legged vertebrates) show these pioneers of land living within the Antarctic Circle 360 million years ago.

 

The evolution of tetrapods from fishes during the Devonian period was a key event in our distant ancestry.  Recently discovered fossils from the latest Devonian Waterloo Farm locality near Grahamstown in the Eastern Cape, South Africa, published today in Science, force a major reassessment of this event.

 

"Whereas all previously found Devonian tetrapods came from localities which were in tropical regions during the Devonian, these specimens lived within the Antarctic circle", explains lead author, Dr Robert Gess of the Albany Museum in Grahamstown, and co-author, Professor Per Ahlberg of Uppsala University in Sweden.

 

The research was supported by the South African Department of Science and Technology and National Research Foundation's Centre of Excellence in Palaeosciences, based at the University of the Witwatersrand, and the Millennium Trust.

 

South Africa's rich natural resources

 

The Minister of Science and Technology, Mmamoloko Kubayi-Ngubane, says South Africa is richly endowed with natural resources, and the country's fossil wealth dates back more than three billion years.

 

"It is uniquely expansive for any one country, and many internationally significant fossil discoveries have been made in our country and are stored in South African Museum collections," says the Minister.

 

She says the country's geographic advantage as a global provider of information on the evolution of life and humanity on Earth stands alongside the country's biodiversity and geographic advantage in astronomy and the science of the southern oceans.

Work on South African paleosciences is of crucial national and international importance, because it provides proof of our shared human origins, the mutual roots that bind all people within a common humanity.  It also provides answers as to what occurred before humans existed, including the evolution of plant and animal life.

The Minister congratulated Dr Gess, saying this groundbreaking discovery places South Africa at the forefront of the study of the evolution of land-living vertebrate animals, including the ancestry of all the wildlife we see in the country's game parks.

 

 

The first African Devonian tetrapods

 

Two new species, named Tutusius and Umzantsia, are Africa's earliest known four‑legged vertebrates by a remarkable 70 million years.  The approximately metre-long Tutusius umlambo (named in honour of Archbishop Emeritus Desmond Tutu) and the somewhat smaller Umzantsia amazana are both incomplete – 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.  Alive, they would have resembled a cross between a crocodile and a fish, with a crocodile-like head, stubby legs, and a tail with a fish-like fin.

 

The Waterloo Farm locality is a roadcut that was first revealed in 2016 after controlled rock‑cutting explosions by the South African National Roads Agency along the N2 between Grahamstown and the Fish River.  This cutting exposed dark grey mudstones of the Witpoort Formation, representing an ancient environment of a brackish tidal river estuary, that contain abundant fossils of animals and plants.

 

The first tetrapod found outside of tropical regions

 

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

 

Devonian tetrapod fossils are found in widely scattered localities.  However, if the continents are mapped back to their Devonian positions, it emerges that all previous finds are from rocks deposited in the palaeotropics – between 30 degrees north and south of the equator.  Almost all finds come from Laurussia, a supercontinent that later fragmented into North America, Greenland and Europe.

 

The much larger southern supercontinent, Gondwana, which incorporated present‑day Africa, South America, Australia, Antarctica and India, has hitherto yielded almost no Devonian tetrapods – only an isolated jaw (named Metaxygnathus) and footprints, both from eastern Australia.

 

Because Australia was the northernmost part of Gondwana, extending into the tropics, an assumption developed that tetrapods evolved in the tropics, most likely in Laurussia.  By extension, it was assumed that the movement of vertebrates from water onto land (terrestrialisation) also occurred in the tropics.  Attempts to understand the causes of these major macro-evolutionary steps therefore focused on conditions prevalent in tropical water bodies.

 

The Waterloo Farm tetrapods not only come from Gondwana, but from its southernmost part – reconstructed to have been more than 70 degrees south, within the Antarctic circle.  Abundant plant fossils show that forests grew nearby, so it wasn't frozen, but it was definitely not tropical, and during winter it would have experienced months of complete darkness.

 

This finding changes our understanding of the distribution of Devonian tetrapods.  We now know that tetrapods occurred throughout the world by the Late Devonian and that their evolution and terrestrialisation could realistically have occurred anywhere.

 

South Africa now adds insights into the emergence of land animals to its incredible fossil record, which includes the transition from reptile-like ancestors to mammals and the evolution of humans.  There is probably not another country on the planet that so fully documents the long and dramatic evolutionary history of our own lineage.

 

 For media enquiries and interviews, contact:

 

Rob Gess

082 306 9099

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Veronica Mohapeloa

083 400 5750

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Please credit Dr Rob Gess and Prof. Per Ahlberg for all pictures and video material.

 

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