Tuesday, September 03, 2013

Scorpion is Gondwana's Oldest Known Land Animal

A postdoctoral fellow from Wits University has discovered the oldest known land-living animal from Gondwana in a remote part of the Eastern Cape. Dr Robert Gess, from the Evolutionary Studies Institute at Wits, discovered the 350 million year old fossilised scorpion from rocks of the Devonian Witteberg Group near Grahamstown. This unique specimen, which is a new species, has been called Gondwanascorpio emzantsiensis.

His discovery has been published in the peer reviewed journal African Invertebrate on Wednesday, 28 August 2013.

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 (350 million years ago), early vertebrates - our four-legged ancestors -had in turn left the water and were feeding on the invertebrates. Although we knew that 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," explained Gess.

No comments: