No, sharks do not have bones. Their skeletons are made of cartilage, the same flexible, \u201crubbery\u201d material found in human ears and noses.\u00a0<\/p>\n
Unlike bone, which is a rigid, mineralized tissue rich in calcium phosphate, cartilage is made mostly of water and protein collagen, making it lighter, flexible, and less rigid.<\/p>\n
Bonelessness is a defining characteristic<\/a> of sharks. They belonged to a group known as cartilaginous fishes, along the likes of rays, skates, sawfish, and chimaeras (better known as ghost sharks<\/a>). As a family, they are among the oldest living groups of jawed vertebrates on the planet.<\/p>\n Do sharks have bones in their jaw?<\/p>\n Sharks don’t even have jawbones in the classic sense. However, some species of shark have jaws that are given extra bite thanks to reinforced cartilage that\u2019s partially calcified<\/a> and hardened.<\/p>\n What are shark teeth made of?<\/p>\n Speaking of their infamous chomping abilities, the only part of a shark’s skeleton not made from cartilage is its teeth, which are made of a hard inner core of dentin, covered by an even tougher outer layer called enameloid.\u00a0<\/p>\n Since cartilage doesn\u2019t fossilize as easily as bone, most of the physical evidence of early sharks is teeth, which preserve much better.\u00a0<\/p>\n In fact, scientists primarily estimate the size of megalodon<\/a> and other extinct shark species by measuring their enormous teeth. Megalodon teeth can be as big as a human hand, suggesting they must have been significantly longer than their living descendants.\u00a0<\/p>\n Sharks\u00a0<\/a>continuously shed and regrow their teeth, leaving tens of thousands behind over a lifetime. It\u2019s not uncommon for lucky beachcombers to stumble upon these prehistoric treasures washed up on sandy shores.<\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/p>\n Why don’t sharks have bones?<\/p>\n Acting like sturdy scaffolding, bones do an excellent job of supporting the structure of animal bodies. Why, then, did sharks not evolve this extremely useful feature?<\/p>\n The simple answer is that cartilage is lighter and more flexible, allowing sharks to swim faster with nimble agility.\u00a0<\/p>\n Unlike other bony fish, sharks don\u2019t have swim bladders, a gas-filled organ that controls buoyancy. Instead, they possess a chunky liver filled with low-density oils that help them float. Their lighter framework also aids them with this feat.\u00a0<\/p>\n A study in 2014<\/a> highlighted another key insight into why sharks never evolved bones. Scientists at San Francisco State University studied the DNA of elephant sharks (Callorhinchus milii), a cartilaginous fish with a peculiar trunk-like snout, and found their genome doesn\u2019t have the genes needed to convert cartilage into bone.<\/p>\n Instead of evolving these genes, their genomes have stayed mostly unchanged for hundreds of millions of years, so cartilage remains their main skeletal material. It might be a similar case for true sharks and other cartilaginous fishes.<\/p>\n How many \u201cbones\u201d do sharks have?<\/p>\n Once again, sharks don\u2019t have bones, as in fully rigid skeletal structures made of calcium phosphate and other chemicals. However, most sharks reportedly\u00a0<\/a>have about 200 to 400 structures made of cartilage that act as supporting structures for their bodies.<\/p>\n