Scientists have found the fossils of Africa’s oldest four-legged vertebrates, a strange pair of Devonian tetrapods that lived within the Antarctic Circle.
Scientists have uncovered the remains of the two earliest-known four-legged creatures to emerge from Africa, Phys.org reports.
These animals, known as tetrapods —ancient vertebrates with four legs that evolved from fish and went on to spawn all the land-living vertebrates we see today — are among the early wave of creatures to grow legs and conquer the land that is now modern-day Africa, Reuters notes.
The two fossils belong to two different species of vertebrates that would have probably looked like a cross between a crocodile and a fish, sporting a crocodile-like head and short stubby legs, but retaining a fish-like tail.
The fossils date back to 360 million years ago and come from a site called Waterloo Farm, near Grahamstown in South Africa. According to Business Insider, their discoverer, Dr. Robert Gess of the Albany Museum in Grahamstown, unearthed the prehistoric remains from 20 tons of fossil-rich shale rock that he salvaged from road construction explosions along the N2 highway between Grahamstown and the Fish River.
Although none of the fossils is complete, Gess explains in the video below that they were both easily recognizable as tetrapod remains. In fact, one of the species was identified solely from a shoulder girdle bone.
Named After Desmond Tutu
Dubbed Tutusius umlambo — in honor of Archbishop Emeritus Desmond Tutu, a cleric and human rights activist involved in the fight against Apartheid — this is the larger of the two species, about a yard (meter) long, and, according to Gess, “the more evolved of the two.”
The other species, named Umzantsia amazana, was identified from several bones and measured about 28 inches (70 cm) in length, having a long, slender lower jaw, filled with small pointed teeth.
If you’re wondering how the two species ended up with their respective names, Gess reveals the meaning behind the chosen denominations.
“When I was thinking about names for them, it occurred to me that these tetrapods led the way from these rather anoxic swamps out into the sunshine. And it seems to me that in many ways, that was a metaphor for what Desmond Tutu had done.”
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.
Here’s where things get interesting (although a fossil named after Desmond Tutu is pretty hard to top).
Oldest Tetrapods In South Africa
First of all, these creatures lived during the Devonian Period (420-359 million years ago) and, as Devonian tetrapods, they are among the earliest ancestors of all vertebrates alive today: mammals, birds, and amphibians.
Being 360-million-years-old, the two fossils precede the previously found early tetrapod remains by a staggering 70 million years, thereby becoming Africa’s first-known four-legged vertebrates.
But the real eye-opener is where they were found. At the time these creatures were alive, Africa was part of a larger southern supercontinent called Gondwana, which also included present-day South America, Australia, Antarctica, and India.
This supercontinent has never yielded a tetrapod fossil before, except for an isolated jaw and some footprints found in eastern Australia, or the northernmost part of Gondwana. All previously discovered Devonian tetrapod fossils hailed from the northern supercontinent known as Laurussia, made up of today’s North America, Greenland, and Europe.
First-Known Devonian Tetrapods In The South Of The Ancient World
The newfound fossils are the first ones ever to emerge from the south of the Devonian world (not just the south of Africa) and bring up the total of known tetrapod species to 13.
Now, the most puzzling thing about finding tetrapod remains in this region is that, during the Devonian Period, South Africa (or the southernmost part of Gondwana) resided within the Antarctic Circle.
This makes Tutusius and Umzantsia the first-ever proof that tetrapods lived all over the world during Devonian times, and not just in tropical regions as previously believed.
“When we think of Devonian tetrapods, the ancestors of all modern vertebrates, we tend to picture amphibian-like creatures emerging from the water into a wet tropical forest or swamp,” Gess and Prof. Per Ahlberg of Uppsala University in Sweden wrote in a study on the new discovery, published on June 8 in the journal Science.
“Whereas all previously found Devonian tetrapods came from localities which were in tropical regions during the Devonian, these specimens lived within the Antarctic circle,” Gess points out.
Their discovery reveals that “tetrapods were not exclusively tropical,” says the paleontologist, which means that they originated anywhere in the world and spread out wherever they found new land to conquer.
The finding challenges the history of life’s evolution on land and “encourages us to rethink the environments in which this important group was shaped,” Gess and Ahlberg show in their paper.
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