The sex lives of ancient turtles: Dying for it Sex often comes at a high price, but rarely so high as that paid by these two fossil turtles. It cost them their lives. The turtles, one of nine couples of a species called Allaeochelys crassesculpta caught in flagrante in the rocks of the Messel pit, near Frankfurt, in Germany, seem to have been the victims of a vicious chemical trick. About 47m years ago, during the Eocene epoch, the Messel pit was the site of a volcanic lake. A paper by Walter Joyce of the University of Tübingen and his colleagues, published in Biology Letters, describes the fossils and speculates how they were killed in the act of copulation. Dr Joyce thinks they mated at the lake's surface, and then dived in copula to the lake-bed to avoid disturbance. Unfortunately, it is a property of many volcanic lakes to be stratified, with poisonous gases dissolved in the water at depth even though their surfaces are pristine. As a result, the amorous chelonians perished.