Debi and I saw this interesting creature at a museum recently, and it was unidentified. Thanks to Debi for researching the following information:
Although sharklike in appearance, sawfish are actually a type of ray and are distinguished by the presence of gill openings on the lower surface of the head rather than on the sides of the head as in sharks. The sawfish snout is elongated into a broad, flat sword with opposing rows of large teeth. When feeding, the sawfish thrashes the saw from side to side, wounding and killing small fish. Sawfish are common in the shallow coastal waters of tropical seas and can ascend moderate distances up freshwater rivers.