Pentecopterus fossil shows human-sized sea scorpion that looks like a Pokémon

1 Sep 2015

Lost to the ages, the fossilised remains of an ancient sea scorpion species dubbed Pentecopterus, which was an ancestor to modern eurypterids but could grow to the size of humans, have been discovered.

Called Pentecoperus after the ancient penteconter Greek galley ships, the truly fearsome creature – that looks somewhat like a Pokémon – was a terror of the sea approximately 467m years ago.

Discovered by a Yale University research team, the fossilised remains of the creature have shown that, at its full length, Pentecopterus could be up to six feet long, with features that included a long head shield and a narrow body.

It also had a series of large, grasping limbs for trapping prey, which eventually saw it be part of the evolution that led to creatures we know today like lobsters, as well as land-borne creatures like spiders and ticks.

Pentecopterus leg sample

Pentecopterus leg sample. Image via James Lamsdell

According to, the fossil specimens were discovered in a meteorite crater near the Upper Iowa River in north-eastern Iowa.

The fossil-rich site was able to reveal well-preserved specimens of not only adult Pentecopterus, but infant ones too, giving unprecedented access to the creature’s development, with the findings being recently published in the journal BMC Evolutionary Biology.

Co-author of the study, and palaeontologist, Derek Briggs said of the find: “The Winneshiek site is an extraordinary discovery. The fossils are preserved in fine deposits of sediments where the sea flooded a meteorite impact crater just over 5km in diameter.”

Likewise, fellow co-author of the study, Huaibao Liu, added: “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.”

Pentecopterus hair

Pentecopterus hair fossilised. Image via James Lamsdell

Colm Gorey was a senior journalist with Silicon Republic