Nectocaris pteryx, one of the many puzzling Cambrian fossils from the Burgess Shale, has been explained. Ninety-one new fossils have been found, and they show that it was a cephalopod, a relative of modern cuttlefish and squids.
The Burgess shale may be the world's most important fossil collection, preserving the soft tissues of many creatures from 505 million years ago, not long after most modern groups of animals -- arthropods, mollusks, and so on -- first appeared. Much has been made over the years of how weird some of them seem. One of the most famous is called Anomalocaris, to emphasize its uniqueness. The thing about science is, though, that over time many things that seem strange are shown to fit into older categories or to be covered by earlier explanations. Not everything -- some things remain mysterious. But it is usually a mistake to put too much theoretical weight on our inability to explain or categorize things.