|“||This must be the most preposterous shark ever.||„|
|— Allen, describing Stethacanthus|
Stethacanthus, ("Chest Spike") also called the Ironing-Board Shark, was a small, primitive shark, some of the first, if not, the first ever to evolve, that lived during the Devonian. It was unique for its flat dorsal fin which resembled an ironing board.
Stethacanthus lived during the Devonian and Carboniferous period, between 370 to 345 million years ago. It shared the waters with Dunkleosteus, Hyneria, Hynerpeton, Bothriolepis, and other fish. Stethacanthus were among the first sharks that had ever evolve.
Being a primitive shark, Stethacanthus was a rather small species of shark, only about no more than two meters long. It looked similar to some of its future descendants, like Hybodus; however, unlike them, its bizarre dorsal fin was thick and flat at the tip and was shaped like an ironing board, hence the colloquial nickname "Ironing-Board Shark".
Near its fluke and near its fins were draping lines of skin which ranged in size. The lines near its fins were long whilst the ones near its fluke were short.
Stethacanthus was a solitary hunter that was constantly on the hunt and preyed upon small animals like the amphibian Hynerpeton and the heavily armoured Bothriolepis. However, during its time, there were larger and far more dangerous predators and Stethacanthus was often preyed upon itself. Large fish, like Hyneria and even Dunkleosteus, had the shark on its menu.
The shark's most striking feature was its flat dorsal fin. As the fin was only featured in the males, it was probably used for courtship and possibly intimidation.