Claim: Cartilage comprises the skeleton of Greenland sharks.
Evidence: It has the longest known lifespan of all vertebrate species -LRB- 392 ± 120 years -RRB- , and is among the largest extant species of shark.
Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton , five to seven gill slits on the sides of the head , and pectoral fins that are not fused to the head.