A 508 million year old trilobite fossil from the Burgess shale in B.C. revealed a clue to how the distant relative of modern animals like spiders, insects and crustaceans had sex. Sarah Losso, an organismic and evolutionary biologist from Harvard University, studied the rare fossil and discovered two previously unknown appendages equipped with claspers used for hanging on to a female during mating. Her research was published in the journal Geology.