An article in the journal “BMC Evolutionary Biology” describes the discovery of fossils of Pentecopterus decorahensis, a sea scorpion that lived in the Ordovician period, about 467 million years ago, in Iowa. It was huge by arthropods standards because it’s estimated that its length could reach 180 cm (almost 6 feet). It’s in fact one of the largest arthropods ever lived and according to James Lamsdell, the lead author of this study, was part of a group of important predators in the Paleozoic era.