facts about sharks

sharks are fishes and most have the typical fusiform body shape. Like other fishes, sharks are ectothermic (cold-blooded), live in water, have fins, and breathe with gills. However, sharks differ from Osteichthyes fish. One difference is that a shark's skeleton is made of cartilage instead of bone. Even though sharks don't have bones, they still can fossilize. As most sharks age, they deposit calcium salts in their skeletal cartilage to strengthen it. The dried jaws of a shark appear and feel heavy and solid; much like bone. These same minerals allow most shark skeletal systems to fossilize quite nicely. The teeth have enamel so they show up in the fossil record too.