Cow shark
A cow shark is a shark in the family Hexanchidae, distinguished from most other sharks by having six or seven pairs of gill slits.
Hexanchidae: A family of sharks with six or seven pairs of gill slits and a single dorsal fin. This family is the taxonomic group that defines cow sharks.
Bluntnose sixgill shark: A large deep-water shark, Hexanchus griseus, found in oceans worldwide. It is the best-known large species in the cow shark family.
Oviparity: A reproductive mode in which embryos develop in eggs that hatch outside the mother's body. Some hexanchids lay eggs, unlike relatives that retain developing embryos.
Deep-sea fisheries: Commercial fishing conducted in deep ocean waters, often using bottom trawls or longlines. Deep-living hexanchids can be caught as targets or bycatch in these fisheries.
Gill slit: An external opening through which water passes from a fish's pharynx after flowing over its gills. The number of these openings is the family's clearest distinguishing feature.
Bigeye sixgill shark: A deep-water shark, Hexanchus nakamurai, distinguished by its notably large eyes. Its large eyes suit the low-light habitats occupied by this hexanchid.
Aplacental viviparity: A reproductive mode in which embryos develop inside the mother without a placenta. Several cow sharks give birth to live young through this mode.
Bycatch: Animals unintentionally captured while fishing for other species. Fishing gear can capture cow sharks even when they are not the intended catch.
Shark: A cartilaginous fish belonging to the subclass Elasmobranchii, with multiple gill slits and replaceable teeth. Cow sharks are members of this broader group of fishes.
Broadnose sevengill shark: A coastal shark, Notorynchus cepedianus, with seven pairs of gill slits and a broad, blunt snout. This active coastal species contrasts with the family's predominantly deep-water members.