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 m 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 cm in length. 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 appearance, sawsharks are distinct from sawfish. Sawfish 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 six 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.


 * Pliotrema warreni Regan, 1906 (Sixgill sawshark)

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.


 * Pristiophorus cirratus (Latham, 1794) (Longnose sawshark)
 * Pristiophorus delicatus Yearsley, Last & W. T. White, 2008 (Tropical sawshark)
 * Pristiophorus japonicus Günther, 1870 (Japanese sawshark)
 * Pristiophorus nancyae Ebert & Cailliet, 2011 (African dwarf sawshark)
 * Pristiophorus nudipinnis Günther, 1870 (Shortnose sawshark)
 * Pristiophorus schroederi S. Springer & Bullis, 1960 (Bahamas sawshark)