冈瓦那发现最古老的陆生动物化石

A postdoctoral fellow from Wits University has discovered the oldest known land-living animal from Gondwana in a remote part of the Eastern Cape¹. Dr Robert Gess, from the Evolutionary² Studies Institute at Wits, discovered the 350 million year old fossilised scorpion³（蝎子） from rocks of the Devonian Witteberg Group near Grahamstown. This unique specimen⁴, which is a new species, has been called Gondwanascorpio emzantsiensis. His discovery has been published in the peer reviewed journal African Invertebrate⁵.

 

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 complexity⁶ throughout the Devonian Period.

 

This initial colonisation of land was closely followed by plant and debris-eating invertebrate（无脊椎的） animals such as primitive⁷ insects and millipedes. By the end of the Silurian period about 416 million years ago, predatory invertebrates⁸ such as scorpions⁹ and spiders were feeding on the earlier colonists¹⁰ 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. 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.

 

For the first time we know for certain that not just scorpions, but whatever they were preying¹¹ 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 ecosystem¹², comprising invertebrates and plants which had all the elements to sustain terrestrial vertebrate life that emerged around this time or slightly later," said Gess.

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