Stethacanthus is an extinct genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

 which lived in the Early Carboniferous epoch, around 360 million years ago. Fossils have been found in Europe and North America.

Stethacanthus was around 70 centimetres (2.3 ft) long, and in many respects, had a typical shark-like appearance. However, it is best known for its unusually shaped dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

, which resembled an anvil

Anvil

An anvil is a basic tool, a block with a hard surface on which another object is struck. The inertia of the anvil allows the energy of the striking tool to be transferred to the work piece. In most cases the anvil is used as a forging tool...

 or ironing board. Small spikes (enlarged versions of the dermal denticles commonly covering shark skin) covered this crest, and the shark's head as well. The crest may have played a role in mating rituals, or used to frighten potential predators.

In popular culture

• In the 2003 TV documentary
  Documentary film
  Documentary films constitute a broad category of nonfictional motion pictures intended to document some aspect of reality, primarily for the purposes of instruction or maintaining a historical record...
  
   Sea Monsters, a spin-off from the 1999 series Walking with Dinosaurs
  Walking with Dinosaurs
  Walking with Dinosaurs is a six-part documentary television miniseries that was produced by BBC, narrated by Kenneth Branagh, and first aired in the United Kingdom, in 1999. The series was subsequently aired in North America on the Discovery Channel in 2000, with Branagh's voice replaced with that...
  
  , a Stethacanthus was briefly shown circling a large shark cage before being scared away by a much larger Dunkleosteus
  Dunkleosteus
  Dunkleosteus is a genus of prehistoric fish, one of the largest arthrodire placoderms ever to have lived, existing during the Late Devonian period, about 380-360 million years ago.This hunter, measuring up to and weighing , was a hypercarnivorous apex predator...
  
  . It reappeared in the 2005 prequel series Walking With Monsters
  Walking with Monsters
  Walking with Monsters is a three-part British documentary film series about life in the Paleozoic, bringing to life extinct arthropods, fish, amphibians, synapsids, and reptiles...
  
  , chasing a Hynerpeton
  Hynerpeton
  Hynerpeton was a basal carnivorous tetrapod that lived in the lakes and estuaries of the Late Devonian period around 360 million years ago. Like many primitive tetrapods, it is sometimes referred to as an "amphibian", though it is not a true member of the modern Lissamphibia...
  
  , only to be eaten by a Hyneria
  Hyneria
  Hyneria was a prehistoric predatory lobe-finned fish that lived during the Devonian period around 360 million years ago. It was approximately 4 meters in length and weighed as much as two tons...
  
  .
• Stethacanthus was featured in Paleoworld
  Paleoworld
  Paleoworld was a documentary television series that was produced for The Learning Channel, and has had a total of 50 episodes. Some consider it to be the largest and most comprehensive paleontology series ever made. The series began in late September 1994 and, after 4 seasons, ended in 1997...
  
  , Episode 5 as the first hunting shark, yet prey for predators like the Rhizodus
  Rhizodus
  Rhizodus is an extinct genus of a rhizodont, a branch of the Sarcopterygii, the bony vertebrate clade that also includes tetrapods....
  
  .