Sawshark

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Not to be confused with sawfish.
Sawsharks
Temporal range: Upper Jurassic–Recent[1]
Shortnose sawshark, Pristiophorus nudipinnis
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Pristiophoriformes
L. S. Berg, 1958
Family: Pristiophoridae
Bleeker, 1859
Genera
Shortnose sawshark
Longnose sawshark

The sawsharks or saw sharks are an order (Pristiophoriformes) of sharks bearing long blade-like snouts edged with teeth, which they use to slash and disable their prey. Most occur in waters from South Africa to Australia and Japan, at depths of 40 metres (130 ft) and below; in 1960 the Bahamas sawshark was discovered in the deeper waters (640 m to 915 m) of the northwestern Caribbean.

Contents

Description and biology [edit]

Sawsharks have a pair of long barbels about halfway along the snout. They have two dorsal fins, but lack anal fins, and range up to 170 centimetres (5.6 ft) in length.[2] Genus Pliotrema has six gill slits, and Pristiophorus the more usual five. The teeth of the saw typically alternate between large and small.

The sharks typically feed on fish, squid, and crustaceans, depending on species. They cruise the bottom, using the barbels and ampullae of Lorenzini on the saw to detect prey in mud or sand, then hit victims with side-to-side swipes of the saw, crippling them.

Although they are similar in appearances, sawsharks are distinct from sawfishes. Sawfishes have a much larger maximum size, lack barbels, have evenly sized rather than alternating sawteeth, and have gill slits on their undersurface rather than on the side of the head.

Genera and species [edit]

There are six described species of sawshark known, in two genera. The latest species, Pristiophorus delicatus, was only discovered in 2008.

Pliotrema [edit]

This genus consists of a single species, the sixgill sawshark, distinguished from Pristiophorus by having six pairs of gill slits. In addition, their rostral sawteeth have prominent transverse ridges on the basal ledges, and the large teeth have posterior serrations.[3]

  • Pliotrema warreni Regan, 1906 (Sixgill sawshark)

Pristiophorus [edit]

Members of this genus have five gill slits. Their rostral sawteeth lack prominent transverse ridges on the basal ledges, and the large teeth are not posteriorly serrated.[3]

Sawshark versus sawfish [edit]

Sawshark and sawfish and are both cartilaginous fishes possessing large saws. However sawfish are not sharks, but a type of ray.

Comparison of sawsharks and sawfishes
Characteristic Sawshark Sawfish Sources
Gill openings on the sides ventral (underside)
[5]
Barbels pair of long barbels about halfway along the saw no barbels
Saw teeth typically alternate between large and small sizes are even
Habitat deep offshore waters shallow coastal waters
[5]
Size relatively small, reaching only 5 feet relatively large, reaching 23 feet
[5]

See also [edit]

Portal icon Sharks portal
Wikispecies has information related to: Pristiophoridae
Wikimedia Commons has media related to: Pristiophoriformes

References [edit]

  1. ^ Froese, Rainer, and Daniel Pauly, eds. (2009). "Pristiophoriformes" in FishBase. January 2009 version.
  2. ^ FishBase
  3. ^ a b Compagno, Leonard J.V. (1984). Sharks of the World: An Annotated and Illustrated Catalogue of Shark Species Known to Date. Rome: Food and Agricultural Organization. ISBN 92-5-101384-5. 
  4. ^ Ebert, D.A. & Cailliet, G.M. (2011): Pristiophorus nancyae, a New Species of Sawshark (Chondrichthyes: Pristiophoridae) from Southern Africa. Bulletin of Marine Science, 87 (3): 501-512.
  5. ^ a b c Ichthyology: Sawfish Biology University of Florida, Museum of Natural History. Retrieved 23 March 2013.

External links [edit]
Topics
Taxonomy
Human
interaction
Extant cartilaginous fish orders
Elasmobranchii
Selachii (sharks)
Batoidea (rays)
Holocephali
Retrieved from "http://en.wikipedia.org/w/index.php?title=Sawshark&oldid=550632729"