Pterygotid Sea Scorpions Not High-Level Predators Of Paleozoic Oceans?

December 29th, 2010 | Related entries: Archeology / History

Acutiramus Impaling

The Paleozoic oceans were previously believed to be dominated by the pterygotid eurypterids commonly known as ‘sea scorpions.’ A team of scientists from New York and New Jersey have apparently discovered clues that the pterygotid eurypterids were not high-level predators in the Paleozoic oceans. This genus probably existed some 470 to 370 million years ago in the seas, which is even before the dinosaurs appeared.

Pterygotid eurypterids as long as 2½ meters are presumably considered as the largest and, arguably, scariest-looking arthropods that have evolved on planet Earth. These species possibly had well-developed legs, and armed with a pair of forward-facing claws. Just like Tyrannosaurus rex, the sea scorpions allegedly had claws with sharp projecting spines. During the research it was pointed out that the mechanical constraints on the sea scorpion Acutiramus’s claw were unable to penetrate the external shell of a medium-sized horseshoe crab. It can therefore be concluded that sea scorpions as well as others dwelling in the seas about 470 to 370 million years ago may not necessarily be insatiable predators.

The practical operational force that can be applied by the claw of Acutiramus without causing damage to it appears not more than 5 Newtons. In order to penetrate the horseshoe crab’s armor, a force of 8-17 Newtons seems to be vital. Richard Laub (Buffalo Museum of Science) and colleagues mention that absence of an ‘elbow joint’ between the claws and the body of Acutiramus limited claw movement. The species apparently preyed on fleeing fish or other swimming animals. With the help of serrated spines, the claws probably captured and shredded the prey. It appears that the predatory capabilities of Acutiramus are not enough to term it as a major predator.

The research is published in the Bulletin of the Buffalo Society of Natural Sciences.

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