Nav: Home

First tetrapods of Africa lived within the Devonian Antarctic Circle

June 07, 2018

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. New-found 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 DST-NRF Centre of Excellence in Palaeosciences, based at the University of the Witwatersrand and the Millennium Trust.

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 (where the tetrapods were discovered) is a roadcut first revealed in 2016 after controlled rock-cutting explosions by the South African National Roads Agency (SANRAL) along the N2 highway between Grahamstown and the Fish River. This cutting exposed dark grey mudstones of the Witpoort Formation that represent 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 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, with only an isolated jaw (named Metaxygnathus) and footprints, being found in 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 movement of vertebrates from water onto land (terrestrialisation) also occurred in the tropics. Attempts to understand the causes of these major macroevolutionary steps therefore focussed 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 will 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 also includes transition to mammals from reptile-like ancestors 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.
-end-


University of the Witwatersrand

Related Evolution Articles:

Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Related Evolution Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Bias And Perception
How does bias distort our thinking, our listening, our beliefs... and even our search results? How can we fight it? This hour, TED speakers explore ideas about the unconscious biases that shape us. Guests include writer and broadcaster Yassmin Abdel-Magied, climatologist J. Marshall Shepherd, journalist Andreas Ekström, and experimental psychologist Tony Salvador.
Now Playing: Science for the People

#514 Arctic Energy (Rebroadcast)
This week we're looking at how alternative energy works in the arctic. We speak to Louie Azzolini and Linda Todd from the Arctic Energy Alliance, a non-profit helping communities reduce their energy usage and transition to more affordable and sustainable forms of energy. And the lessons they're learning along the way can help those of us further south.