Stethacanthus (Alain Beneteau).


Stethacanthus (Greek for "chest spike"); pronounced STEH-thah-CAN-thuss


Oceans worldwide

Historical Period:

Late Devonian-Early Carboniferous (390-320 million years ago)

Size and Weight:

Two to three feet long and 10-20 pounds


Marine animals

Distinguishing Characteristics:

Small size; strange, ironing-board shaped back structure on males


About Stethacanthus

In most ways, Stethacanthus was an unremarkable prehistoric shark of the late Devonian and early Carboniferous periods--relatively small (a maximum of three feet long and 20 or so pounds) but a dangerous, hydrodynamic predator that posed a constant menace to small fish as well as other, smaller sharks.

What really set Stethacanthus apart was the strange protrusion--often described as an "ironing board"--that jutted out from the backs of the males. Because the top of this structure was rough, rather than smooth, experts have speculated that it may have served as a docking mechanism that attached males securely to females during the act of mating.

It took a long time, and a lot of fieldwork, to determine the exact appearance and function of this "spine-brush complex" (as the "ironing board" is called by paleontologists). When the first Stethacanthus specimens were discovered, in Europe and North America in the late 19th century, these structures were interpreted as a new type of fin; the "clasper" theory was accepted only in the 1970's, after it was discovered that only males possessed "ironing boards." (Some paleontologists have suggested a second use for these structures; from a distance, they look like giant mouths, which might have scared away larger, near-sighted predators).

Given the large, flat "ironing boards" protruding from their backs, Stethacanthus adults (or at least the males) couldn't have been particularly fast swimmers. That fact, combined with the unique arrangement of this prehistoric shark's teeth, point to Stethacanthus having been primarily a bottom-feeder, though it might not have been adverse to actively chasing down slower fish and cephalopods when the opportunity presented itself.

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Strauss, Bob. "Stethacanthus." ThoughtCo, Mar. 7, 2017, Strauss, Bob. (2017, March 7). Stethacanthus. Retrieved from Strauss, Bob. "Stethacanthus." ThoughtCo. (accessed March 23, 2018).