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In contrast, bony fishes have a single outer bony gill covering called an operculum. Most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind the head. The anterior edge of a gill slit is motile, moving outward to allow water to exit, but closing to prevent reverse flow.
Batoid gill slits lie under the pectoral fins on the underside, whereas a shark's are on the sides of the head. Most batoids have a flat, mantle-like body, with the exception of the guitarfishes and sawfishes , while most sharks have a spindle-shaped body.
The broadnose sevengill shark (Notorynchus cepedianus) is the only extant member of the genus Notorynchus, in the family Hexanchidae. It is recognizable because of its seven gill slits, while most shark species have five gill slits, with the exception of the members of the order Hexanchiformes and the sixgill sawshark. This shark has a large ...
Bonaparte's original definition of Elasmobranchii was effectively identical to modern Chondrichthyes, and was based around gill architecture shared by all 3 living major cartilaginous fish groups. During the 20th century it became standard to exclude chimaeras from Elasmobranchii; along with including many fossil chondrichthyans within the group.
Like other fish, sharks extract oxygen from seawater as it passes over their gills. Unlike other fish, shark gill slits are not covered, but lie in a row behind the head. A modified slit called a spiracle lies just behind the eye, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks.
The megamouth shark is an extremely rare species of deepwater shark, and the smallest of the three filter-feeding sharks. Since its discovery in 1976, only a few megamouth sharks have been seen, with 55 specimens known to have been caught or sighted as of 2012, including three recordings on film.
The Bluntnose sixgill shark is one of four shark species that have six gill pairs. Other three are - Frilled shark (Chlamydoselachus anguineus), Bigeyed sixgill shark (Hexanchus nakamurai) [4]) and Atlantic sixgill shark (Hexanchus vitulus) The bluntnose sixgill shark has a large body and long tail. The snout is blunt and wide, and its eyes are ...
The Hemiscylliidae are a family of sharks in the order Orectolobiformes, commonly known as longtail carpet sharks and sometimes as bamboo sharks.They are found in shallow waters of the tropical Indo-Pacific.