Palaeontology: Girls and boys come out to play

To have and to hold SEX is ubiquitous, but sexual intercourse is not. On dry land, it is more or less de rigueur. Sperm and eggs risk dessication otherwise. Mammals, birds and reptiles do it. Insects do it. Even snails do, it--firing darts at each other as part of the preliminaries. But many creatures live in the oceans, and a lot of them simply broadcast eggs and sperm into the water and hope that these will meet. Even those marine animals that do come together to mate--bony fish, for example--...