Ancestor of arthropods had the mouth of a penis worm

Fresh evidence from a series of expeditions to North Greenland have led palaeontologists to solve an age-old mystery about a distinctive group of arthropods. Imagine a meter long worm with 12 stubby legs and matching sets of flaps running down the body. On the head is a large pair of spiny appendages used for grasping prey that transport victims into a circular mouth with several rows of teeth. For years, scientists have disagreed over whether this mouth belonged to the Anomalocaris , the largest sea predator from the Cambrian Period, or was comparable to the penis worm, a subset of priapulids, a category of marine worms that were diverse in the Cambrian. Now fresh evidence has led scientists from the University of Bristol and the Natural History Museum to resolve the mystery, discovering that the mouth apparatus was attached to a primitive relative to the arthropods, called Pambdelurio n. "The mouth is a spitting image of the Sarlacc from Star Wars," says Bristol University's Dr Jakob Vinther , referring to the beast with the gaping mouth in the sand dunes of Tatooine in the 'Return of the Jedi'. During a series of expeditions to North Greenland, the team of researchers unearthed exquisite fossil specimens of Pambdelurion , an extinct relative of modern arthropods, which lived in the oceans 520 million years ago. These fossils now form the mountains of the northernmost part of Greenland.