The skeleton of a shark is mainly cartilage. The sharks have at least 230 bones.
Shark teeth are relics of shark evolution and biology. Shark skeletons are composed entirely of cartilage. Often the only parts of the shark to survive as fossils are teeth. Fossil shark teeth have been dated back hundreds of millions of years. The most ancient types of sharks date back to 450 million years ago, and they are mostly known from their fossilized teeth. The most common, however, are from the Cenozoic Era (65 million years ago).
The teeth of sharks are not attached to the jaw, but embedded in the flesh, and in many species are constantly replaced throughout the shark's life. When they lose a tooth they will replace then within 7 to 8 days. All sharks have multiple rows of teeth along the edges of their upper and lower jaws. New teeth grow continuously in a groove just inside the mouth and move forward from inside the mouth on a "conveyor belt" formed by the skin in which they are anchored. In some sharks rows of teeth are replaced every 8-10 days, while in other species they could last several months. The lower teeth are primarily used for holding prey, while the upper ones are used for cutting into it. The teeth range from thin, needle-like teeth for gripping fish to large, flat teeth adapted for crushing shellfish.
A shark can have hundreds of teeth in its jaw. Sharks, as well as other Chondrichthyes, have the ability to replace their teeth if they become damaged during feeding or fall out due to natural causes. Many icthyologists have suggested that sharks can lose tens of thousands of teeth within the span of a few years.
Megalodon Teeth.Carcharodon megalodon teeth are among the most sought after types of shark teeth in the world. These teeth are in extremely high demand by collectors and private investors, and they can fetch steep prices. This shark lived during the Miocene and Pliocene eras, roughly about 16 to 1.5 million years ago. Its teeth on average range between 1.5 to 6.5 inch in length. But the largest teeth of this shark are more than 7 inch long. These huge teeth indicate that the megalodon could grow up to more than 16 m (52.5 ft) long, growing bigger than the largest fish alive in the world today, the whale shark.
Large numbers of megalodon teeth have been discovered across both coasts of the United States. The most plentiful locations within the U.S. are the Carolinas, Georgia, and parts of Florida and Virginia.
These large and magnificent sharks disappeared relatively close to the rise of modern man. However, there have been many unconfirmed reports of large animals resembling large, carnivorous, sharks.
Megalodon teeth have been discovered that some argue date as recently as 10,000 to 15,000 years ago. This claim is based on the discovery of two teeth by the HMS Challenger scientific expedition. These teeth were dated by estimating the amount of time it took for manganese to accumulate on them, although it is quite possible the teeth were fossilized before being encrusted.
Transitional teeth.Identifying shark teeth is tedious work, especially with all of the damaged, worn, and different teeth. It is even more difficult because of the so-called "In-Between Teeth". These are teeth that are from a shark species that was evolving into another, different species. An example of this can be seen with Carcharocles auriculatus teeth that were in the state of evolving into Carcharocles angustidens. These are teeth that are no longer auriculatus, but not yet angustidens either.
Great White/Mako Transitional Teeth.The most common and most referred to transitional shark teeth are the ones coming from what is believed by some to be an unusual form of great white shark. Great white shark transitional teeth are often characterized for their wide crowns. These teeth can also be identified by the way the serrations fade, being more pronounced near the root, and disappearing close to the tip of the tooth.
Many paleontologists now believe that these transitional teeth represent the evolutionary path between Isurus hastalis and the Great white shark. The evolutionary history of the great white shark and its relation to megalodon are hotly debated.
Because of their transitional state, these teeth are rare. These teeth are prized by collectors, hobbyists, and museums.