This article was originally published at The Conversation. The publication contributed the article to Live Science's Expert Voices: Op-Ed & Insights.
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.
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