September 3, 2013
Earliest Known Scorpion Fossil Discovered In South Africa
Lee Rannals for redOrbit.com - Your Universe Online
Scientists publishing a study in the journal African Invertebrate say they have discovered a 350-million-year-old fossilized scorpion. The specimen, discovered in rocks from the Devonian Witteberg Group near Grahamstown, is a new species of scorpion called Gondwanascorpio emzantsiensis.
Dr Robert Gess, from the Evolutionary Studies Institute at Wits University, discovered the specimen, which is said to be the oldest known land-living animal in the Southern Hemisphere supercontinent, Gondwana. He explained that early life was initially confined to the sea and the process of moving life to land began during the Silurian Period about 420-million-years-ago. Plants were the first living species to move from water to land, and these gradually increased in size and complexity throughout the Denovian period.
Gess says this initial colonization of land was closely followed by plant and debris-eating invertebrate animals like primitive insects and millipedes. However, by the end of the Silurian period about 416 million years ago, predatory invertebrates like scorpions and spiders began feeding on the original insects. By the Carboniferous period, 360 million years ago, vertebrates had left the water and began feeding on the invertebrates.
Laurasia, a landmass that comprised of North America and Asia, was inhabited by diverse invertebrates by the late Silurian period and during the Denovian period. During this period, this supercontinent was separated from the southerly-positioned Gondwana by a deep ocean.
"Evidence on the earliest colonization of land animals has up till now [sic] 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.
He said that this 350-million-year-old scorpion allows scientists to confirm some long-held ideas about early life.
"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,” said Gess.
In 2007 scientists discovered a fossilized claw of an ancient sea scorpion that shows these archaic arachnids were much larger than previously thought. The 390-million-year-old fossil would make the scorpion ancestor eight feet long and as big as a car. Some geologists believe gigantic sea scorpions evolved due to higher levels of oxygen in the atmosphere, while others believed it was due to an "arms race" alongside their likely prey.
“The competition between this scorpion and its prey was probably like a nuclear standoff, an effort to have the biggest weapon,” Simon Braddy, a University of Bristol paleontologist, said at the time. “Hundreds of millions of years ago, these sea scorpions had the upper hand over vertebrates – backboned animals like ourselves.”