<P> A shark tooth is one of the numerous teeth of a shark . A shark tooth contains resistant calcium phosphate materials . Sharks continually shed their teeth; some Carcharhiniformes shed approximately 35,000 teeth in a lifetime, replacing those that fall out . There are four basic types of shark teeth: dense flattened, needle - like, pointed lower with triangular upper, and non-functional . The type of tooth that a shark has depends on its diet and feeding habits . </P> <P> In some formations, shark's teeth are a common fossil . These fossils can be analyzed for information on shark evolution and biology; they are often the only part of the shark to be fossilized . Fossil teeth comprise much of the fossil record of the Elasmobranchii, extending back to hundreds of millions of years . Shark teeth are also useful in conducting research about the structure of teeth, shark migration patterns, and identifying shark species . </P> <P> The most ancient types of sharks date back to 450 million years ago, during the Late Ordovician period, and are mostly known by their fossilised teeth . However, the most commonly found fossil shark teeth are from the Cenozoic era (the last 66 million years). </P>

How many teeth are in a sharks mouth