Meet Pentecopterus decorahensis, the creature that would have eaten you were you a tasty fishy 460m years ago: "It was obviously a very aggressive animal. It was a big angry bug."
Those are the words of James Lamsdell of Yale University, author of a study on the nasty thing.
The creature grew to 170 centimtres (5ft 7in) and had a dozen claw arms sprouting from its head, as well as a spiked tail. Geologists at the Iowa Geological Survey found 150 pieces of fossils about 18 metres under the Upper Iowa river, part of which had to be temporarily dammed to allow them to collect the specimens.
Scientists at Yale University determined they were a new species from about 460m years ago when Iowa was under an ocean.
The study was published in the journal BMC Evolutionary Biology. It's like reading about a very complex fossilized puzzle.
Despite the fragmentary nature of the material, the comprehensive representation of the morphology allows Pentecopterus to be reconstructed (Fig. 20). The taxon bears a number of similarities to Megalograptus[5], including the typical megalograptid guttalate ornamentation and a number of features of the prosomal appendages, notably the randomly-oriented armature on the distinctly swollen podomeres of appendage IV and the narrow gnathobase bearing multiple rows of small teeth on the coxa of appendage V…The newly described eurypterid Pentecopterus decorahensis from the Winneshiek Lagerstätte is the earliest described representative of the group, pushing our knowledge of Eurypterida back some 9 million years to the Darriwilian in the Middle Ordovician. Pentecopterus shows clear affinities with megalograptids, a highly distinct group of large predatory eurypterids known solely from the Ordovician of North America.
This also sounds like a great candidate for the "swarming monster of the month" for the cover art of a traditional mens' adventure magazine.
