Allaeochelys

Allaeochelys is an extinct genus of pig-nosed turtle.
Fossils of the species "Allaeochelys crassesculpta" have been found in the Messel Pit near Darmstadt, Germany in pairs fossilised in the coital position.
It is believed to be the only example in the fossil record of vertebrates mating.
Dr Walter Joyce of the University of Tübingen said that "We've demonstrated quite clearly that each pair is a male and a female, and not, for example, just two males that might have died in combat...People had long speculated they might have died while mating, but that's quite different from actually showing it."