New Fossil: Grasping, Armored, Greekship-like Predator

Imagine something that is both a sea scorpion and a sleek, fearsome Greek ship, and you have the features of a fossil found in Iowa. Researchers determined that this is the oldest-known species of the eurypterid, dating back 467 million years. It was a fierce Paleozoic predator and is related to modern spiders, lobsters and ticks.

Researchers from Yale University and the University of Iowa named this new species Pentecopterus, after the ancient Greek warship penteconter. The name suits this aquatic creature that was found armed with a long head shield, a narrow body, and large, grasping limbs--most likely used to catch its prey. 

"Pentecopterus is large and predatory, and eurypterids must have been important predators in these early Palaeozoic ecosystems," James Lamsdell, a postdoctoral associate at Yale University and lead author of the study, said in a new release.

According to their study, recently published in BMC Evolutionary Biology, more than 150 fossil fragments of the new species were collected from an area called the Winneshik site, which is the upper layer of a fossil bed in a meteorite crater in northeastern Iowa. Located near the Upper Iowa River, this layer is 27 meters thick and composed of sandy shale.  

"This shows that eurypterids evolved some 10 million years earlier than we thought, and the relationship of the new animal to other eurypterids shows that they must have been very diverse during this early time of their evolution, even though they are very rare in the fossil record," Lamsdell said.

Researchers were able to collect the fossils during a temporary damming of the river in 2010. From this site, well-preserved adult and juvenile specimens were found, which gave the researchers a lot of information with which to work.

"The Winneshiek site is an extraordinary discovery," Derek Briggs, co-author and paleontologists from Yale, said in the release. "The fossils are preserved in fine deposits of sediments where the sea flooded a meteorite impact crater just over 5 km in diameter."

Huaibao Liu, co-author from the Iowa Geological Survey and the University of Iowa, said: "What's amazing is the Winneshiek fauna comprise many new taxa, including Pentecopterus, which lived in a shallow marine environment, likely in brackish water with low salinity that was inhospitable to typical marine taxa. The undisturbed, oxygen-poor bottom waters within the meteorite crater led to the fossils' remarkable preservation. So this discovery opens a new picture of the Ordovician community that is significantly different from normal marine faunas."

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