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Pristiophorus

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Title: Pristiophorus  
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Subject: List of sharks, Bahamas sawshark, Shortnose sawshark, Japanese sawshark, Longnose sawshark, Eastern Australian sawshark, Philippine sawshark, Dwarf sawshark, Undescribed taxon, Tropical sawshark
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Pristiophorus

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


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.

Description and biology

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

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

Pliotrema

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]

Pristiophorus

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]

Comparison with sawfish

Sawshark and sawfish and are both cartilaginous fishes possessing large saws. However sawfish are not sharks, but a type of ray. The gill slits of the sawfish are positioned on the underside like a ray, but the gill slits of the sawshark are positioned on the side like a shark. Another clear difference is that the sawfish has no barbels and the sawshark has a prominent pair halfway along the saw. The sawshark uses these like other bottom fish, as a kind of antennae, feeling the way along the ocean bottom until it finds some prey of interest.

Comparison of sawsharks and sawfishes
Characteristic Sawshark Sawfish Sources
Gill openings on the sides ventral (underside)
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
Size relatively small, reaching only 5 feet relatively large, reaching 23 feet

See also

Sharks portal

References

External links

  • FishBase info for Pristiophoridae
  • Reefquest page
  • Checklist of Living Sharks
  • NOVA Online photo of longnose sawshark
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