This must be the most preposterous shark ever.
— Allen, describing Stethacanthus

Stethacanthus (name meaning "Chest Spine"), colloquially known as the Ironing-Board Shark, was a small, primitive shark that originated during the Devonian. Some of the first, if not, the first ever to evolve and a size of only 2 meters long, it was unique for its flat dorsal fin which resembled an ironing board.


Era & DiscoveryEdit

Stethacanthus lived during the Devonian and Carboniferous period, between 370–345 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.

The several species of Stethacanthus discovered in the late 1800s were established based solely upon isolated spines, which initially confused paleontologist John Strong Newberry into thinking the spines constituted a new kind of fin.

Physical AttributesEdit

Stethacanthus was a relatively small, primitive shark. Though at around 2–6 feet in length, it was still a tenacious predator, whilst being relatively primitive compared to later sharks, it would have been a highly advanced shark at the time posing a threat to the far more primitive forms still abundant at the time. However advanced this shark was though, the large Hyneria and Arthodire Placoderm apex predators, such as the largest of them all Dunkleosteus, would have regularly attacked and devoured sharks like Stethacanthus. They were minor predators, in a world dominated in the seas by the Placoderms.

It looked similar to some of the shark species that would evolve later, like Hybodus, but unlike them, its dorsal fin was thick and flat at the tip and was shaped like an ironing board, hence the colloquial name. 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.

Behavior & TraitsEdit

Stethacanthus was a solitary hunter that preyed upon small animals, like the amphibian Hynerpeton and the heavily armored Bothriolepis. Stethacanthus was however a relatively small-sized predator, and as such, it would have restricted its diet to small fish, cephalopods and perhaps some types of arthropod, such as trilobites. However, during its time, there were larger and far more dangerous predators and Stethacanthus was often preyed upon itself. Large fish like Hyneria and Dunkleosteus had the shark on its menu.

It would have been capable of swimming at moderately fast speeds, and would have hunted by chasing small fish or grabbing animals from the seabed, as many modern reef sharks do.

The shark's most obvious but striking feature was its flat, strange-shaped dorsal fin, which has a wide, flattened top covered in hundreds of rough, tooth-shaped scales. A patch of the same rough scales was also found on the top of its head. Only the males had this fin, which means that it probably played a role in mating, possibly as part of a courtship display or even to possibly intimidate rivals. However, it has also been suggested that when viewed from certain angles the fin and the rough-shaped scales could make Stethacanthus look as though it had a gigantic, tooth-laden mouth. This might have served to scare off potential predators. Nonetheless, even though Stethacanthus was a reasonable-sized shark for its time, it would have stood little chance if confronted by some of the giant placoderms like Dunkleosteus and large fish like Hyneria with which it shared the seas.