Sawfish

The sawfish are a family of rays which have a long body, like a shark. One feature that separates a sawfish from other rays is its long, saw-like snout. On either side of this rostrum are little teeth like a saw. 

Sawfish have a mouth, nostrils, and gill slits under their body, just like a ray. Also, their pectoral fins are enlarged, like those of a ray. Also like rays, when they settle on the bottom, they take in water through two spiracles just behing the eyes. This gets water to the gills without sand.Nelson J.S. 2006. Fishes of the World. 4th ed, Wiley.

Several species can grow to about .Froese, Rainer, and Daniel Pauly, eds. 2009. "Pristidae" in FishBase. FishBase online

 Rostrum 
The sawfish's most distinctive feature is the saw-like rostrum. The rostrum is covered with motion- and electro-sensitive pores. These allow sawfish to detect movement and even heartbeats of prey hiding under the ocean floor. The rostrum serves as a digging tool to unearth buried crustaceans. 

If a suitable prey swims by, the normally lethargic sawfish springs from the bottom and slashes at it with its saw. This generally stuns or injures the prey sufficiently for the sawfish to devour it. Sawfish also defend themselves with their rostrum, against predators such as sharks and intruding divers. The 'teeth' protruding from the rostrum are not real teeth, but modified tooth-like structures called denticles.

 References 

Category:Rays