Source: news.sciencemag.org - Monday, August 31, 2015 Scientists have unearthed the oldest known species of a long-extinct group known as sea scorpions, a find that could mean the ancient creatures may have an even older origin than previously thought. Team members have dubbed the newly described predator Pentecopterus after the penteconter, a type of ancient Greek warship that roughly mirrors the creature’s body shape (artist’s reconstruction shown above). More than 150 fossil fragments of the animals, some of them possibly bits of molted exoskeleton, have been excavated from 467-million-year-old rocks in northeastern Iowa—rocks that are about 9 million years older than those that held fossils of the previously oldest known species . (Sea scorpions, more formally known as eurypterids, were arthropods, a group that includes insects, spiders, and crabs as well as their extinct kin such as trilobites.) Adults of the newly described predator were probably about 1.7 meters (5.6 feet) long, but some of the fossil fragments came from juveniles that may have measured between 10 and 15 centimeters (4 to 6 inches) in length, the researchers report online today in BMC Evolutionary Biology . Unlike all other known living or extinct arthropods, some of Pentecopterus ’ limbs dramatically changed shape as the individuals grew—which suggests that small-clawed youngsters may have probed through sediments for tiny prey whereas adults grabbed larger, more mobile victims. The antiquity of these creatu All Related | More on Scientists
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