HEXANCHIDAE COW SHARKS
Cow sharks are a family, the Hexanchidae, of sharks belonging to the order Hexanchiformes. They can be characterized by having an additional pair or two of gill slits; therefore, 6 or 7 pairs of gill slits. They have slender to stalky cylindrical bodies in appearance. They have a ventral mouth with large, compressed, comb-like bottom teeth and smaller cuspidate teeth in the upper jaw. They have a single spineless dorsal fin that is high and angular. Their pectoral fins are angular and larger than the pelvic fins. The anal fin is single and smaller than the dorsal fin. The caudal fin has a marked sub-terminal notch. They range from 4.6-18 feet in length when mature.
Cow sharks are ovoviviparous, and have a range of items within their diet from large fish, crustaceans, carrion, to other sharks
Cow sharks are considered the most primitive family of all shark families. Their skeletons resemble those of ancient extinct forms, with few modern adaptations. Their excretory and digestive systems are also unspecialized, suggesting they may resemble those of primitive shark ancestors. A possible hexanchid tooth is known from the Permian of Japan, making the family a possible extant survivor of the Permian-Triassic extinction. Many of the sharks under this family are extinct. Please refer to the order Hexanchiformes order page and our Primitive Sharks section in the Planet Shark Academy.
Below are the four living species belonging to the family Hexanchidae or Cow sharks.