Giant Sea Scorpion Fossil Discovered

The fossil of a previously unknown species of giant, predatory sea scorpion has been discovered, and is described this week inBMC Evolutionary Biology.

This giant predator measures more than 1.7 meters in length and inhabited the deep ocean 460 million years ago, making it 10 million years more ancient than the oldest previously known species of eurypterid (sea scorpion).

The authors named the new speciesPentecopterus decorahensisafter a Greek warship known as the 'Penteconter'.

"The outline from above kind of looks like these Greek warships." says lead author James Lamsdell. "It was very sleek, and the head is projected into this strange prow like structure which just looks like the front of the ship. And then there are paddles coming off the back of the head which would have helped it to swim... This thing was just a really bizarre animal, it was really strange looking"

James had the painstaking task of constructing this fossilised jigsaw. He pieced together parts of fragmented exoskeleton that the animal had moulted and which had become encased in the rock.

"I essentially had a jigsaw puzzle where someone had removed some of the pieces, and then dumped a bunch of other jigsaw puzzles in with it".

This remarkable fossil was exceptionally well preserved due to its location within an ancient meteorite impact crater that is almost entirely submerged by the Upper Iowa River. The environment is very deep and experiences very little wave action. Coupled with lower than normal oxygen levels, this helped to delay the normal decay process.

"The preservation really is remarkable, I've never seen anything like it before", said James.

Exceptional preservation enabled the researchers to interpret the functions of certain parts of the body such as the rearmost limbs which acted as paddles, or second and third pairs of limbs that were likely used to capture prey.