Not some strange new craze, but the more we look the more we see! It has taken 80 years, but we are a step closer to understanding the evolution of sexual reproduction in vertebrates (creatures with a back bone). Research published in Biological Reviews last week has demonstrated that male genital organs were present 390 million years ago in ancient fish. The Placoderms were a diverse group of fish with characteristic armour plating on their heads and shoulders. This new research documents the diverse array of genital appendages in male Placoderms. This demonstrates how early sexual dimorphism (the different appearence between males and females) appeared in our own branch of the tree of life. Finally, rather than spend months on fieldwork all the fossils were sat waiting to be sexed in museums! Further proof of the importance of museum collections.
We humans use the euphemism for sex that “we like to get a leg over” but the first jawed vertebrates – the placoderms – they liked to get a leg in. They were the first back-boned creatures to evolve male genital organs, or claspers, supported by a bony internal skeleton. What’s even more peculiar is that, unlike the cartilaginous claspers of modern sharks, which are a modified part of the pelvic fin, our new research has shown that in placoderms they were basically a separate set of paired appendages.