Scientists have discovered a 350-million-year-old fossilised scorpion in South Africa which is the oldest known land animal to have lived on the ancient supercontinent of Gondwana.
Dr Robert Gess,from the Evolutionary Studies Institute at The University of the Witwatersrand,Johannesburg,discovered the fossilised scorpion from rocks near Grahamstown in South Africa’s Eastern Cape.
This unique specimen,which is a new species,has been named Gondwanascorpio emzantsiensis.
Explaining his discovery,Gess said that early life was confined to the sea and the process of terrestrialisation – the movement of life onto land – began during the Silurian Period roughly 420 million years ago.
The first wave of life to move out from water onto land consisted of plants,which gradually increased in size and complexity throughout the Devonian Period.
This initial colonisation of land was closely followed by plant and debris-eating invertebrate animals such as primitive insects and millipedes.
By the end of the Silurian period about 416 million years ago,predatory invertebrates such as scorpions and spiders were feeding on the earlier colonists of land.
By the Carboniferous period (360 million years ago),early vertebrates – our four-legged ancestors – had in turn left the water and were feeding on the invertebrates.
Laurasia – the single northern landmass then comprising what is today North America and Asia – was inhabited by diverse invertebrates by the Late Silurian and during the Devonian,this supercontinent was at the time separated from the southerly positioned Gondwana by a deep ocean.
“Evidence on the earliest colonisation of land animals has up till now come only from the northern hemisphere continent of Laurasia,and there has been no evidence that Gondwana was inhabited by land living invertebrate animals at that time,” said Gess.
“For the first time we know for certain that not just scorpions,but whatever they were preying on were already present in the Devonian. We now know that by the end the Devonian period Gondwana also,like Laurasia,had a complex terrestrial ecosystem,comprising invertebrates and plants which had all the elements to sustain terrestrial vertebrate life that emerged around this time or slightly later,” he said.
The discovery has been published in the journal African Invertebrate.