July 19, 2018 by John Long And Marion Chevrinais, The Conversation
Euphanerops, a primitive jawless fish from the World Heritage site at Miguasha, Quebec, which has now been found to have paired hind limb structures and copulatory sex organs. Credit: François Miville-Deschênes with permission, Author provided
Fossil discoveries from the Devonian rocks of Scotland and Australia first revealed that the earliest jawed fishes, the placoderms, reproduced using copulation in much the same way as sharks and rays do today.
They also had the first paired pelvic skeletons, the precursor to the hind paired fins – and legs – of all animals. Their paired reproductive organs, called "claspers", probably developed in the same way as limbs.
The appearance of jaws and teeth in the first vertebrates was thus intimately linked to the origin of paired hind limbs (pelvic girdles) and an advanced kind of sexual reproduction.
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