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Old pseudoscorpion had modern features.

Old pseudoscorpion had modern features

Scientists digging in upstate New York have discovered 380-million-year-old fossils of a tiny land-dwelling animal called a pseudoscorpion, pushing the history of this creature back to Earth's Devonian period, when animal communities were beginning to develop on land.

Though only distantly related to their namesake, pseudoscorpions resemble miniature scorpions without the trademark tail and stinger. Today, more than 3,000 known species exist around the world. Before the new finds established the great antiquity of these animals, the pseudoscorpion fossil record went back only 35 million years. William A. Shear of Hampden-Sydney (Va.) College, Wolfgang Schawaller of the State Museum of Natural History in Stuttgart, West Germany, and Patricia M. Bonamo of the State University of New York at Binghamton describe the latest fossils in the Oct. 12 NATURE.

Despite their great age, the Devonian pseudoscorpions do not seem primitive compared with modern species, according to Shear. He says this suggests that evolutionary forces have not severely altered pseudoscorpions since then.

"These things developed adaptations to a particular way of life, and that has seemed to be suitable for all the rest of time since then," says William B. Muchmore, an expert in pseudoscorpions at the University of Rochester (N.Y.).

Shear and Bonamo have found many other types of Devonian predatory arthropods at the same site, including the oldest known centipede and spider fossils, which they will describe in the Oct. 27 SCIENCE. So far, they have found no evidence there of herbivorous animals that would have filled in the food web.

The first land animals appear in the fossil record at the end of the Silurian period and the beginning of the Devonian period, roughly 400 million years ago. But many of these earliest fossils, including the newly found pseudoscorpions, show highly evolved features, including evidence of well-developed sensory hairs. Shear says this indicates either that early land creatures evolved rapidly after leaving an aquatic environment or that animals established themselves on land long before they appeared in the fossil record -- a distinct possibility because of the rarity of fossils from that time. If the latter is true, the earliest land animals may have lived on continents before vascular plants developed. In that case, the researchers say, these tiny arthropods -- which today live under leaves and soil -- probably would have dwelled in the crevices of bacterial and algal mats that scientists think carpeted the Devonian ground.
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Title Annotation:fossil
Author:Monastersky, R.
Publication:Science News
Date:Oct 21, 1989
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