Scientists have unearthed South African fossils of prehistoric Devonian Period amphibians believed to be the earliest known four-legged vertebrates at a site called Waterloo Farm in Grahamstown.
The two tetrapods fossils were named Tutusius and Umzantsia. The scientists described them as resembling a cross between an alligator and a fish. Since they were classified as amphibians, scientists deduced they could eat small fish while in water and tiny invertebrates while on land.
The importance of the discovered fossils, however, lies in the environment where they were unearthed.
Devonian tetrapods are being touted as the ancestors of all vertebrates, being the amphibious, aquatic tetrapods that first colonized the land. As first scientifically established, their evolution takes place in warm tropical places.
Now, with the South African fossils, it was finally known that they have also resided in colder environments. Specifically, within the Antarctic circle some 360 million years ago.
Tutusius And Umzantsia
The paleontologists identified Tutusius from a piece of its shoulder girdle bone. The species was estimated to be about 3 feet long. The paleontologists decided to name the species after Desmond Tutu, the South African human rights activist.
Umzantsia, meanwhile, measured about 2.3 feet long, has a slender lower jaw, and small pointed teeth.
"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 paleontologists working with the South African Center of Excellence in Palaeosciences wrote in a study published in the journal Science.
Rewriting History Of Early Life On Land
Devonian tetrapod fossils are practically found everywhere in the world. However, they were not found in ancient supercontinent Gondwana, which, in the present day, became Africa, South America, Australia, Antarctica, and India. The only fossil found of these amphibian tetrapods was a jaw and footprints in eastern Australia.
Most, if not all, of their fossils, were discovered in another ancient supercontinent called Laurussia, which, at present day, are North America, Greenland, and Europe.
Previously drawn conclusions stated that these amphibians moved out from the water on to the land through tropical regions until finally ending in Laurussia. Hence, subsequent studies about their evolution to become land species have only factored in the influence of tropical conditions.
However, fossils of both Tutusius and Umzantsia were found to have come from the southernmost part of Gondwana.
"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.
Together with Per Ahlberg, the coauthor of the study, the whole team concluded that while tetrapods occurred in the world by the Late Devonian period, their evolution and migration to land could also have happened elsewhere in the world.