Shark teeth

Shark teeth are relics of  and. Shark skeletons are composed entirely of. Often the only parts of the shark to survive as 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 (65 million years ago).

== Overview ==

A shark can have hundreds of teeth in its jaw. Sharks, as well as other, 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. 

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 working tooth it will be replaced by the next tooth behind it. 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. Typically a shark have two to three working rows of teeth with 20 to 30 teeth in each row, e.g. a have about 300 teeth in each row. The replacement rate has not been measured in most sharks but normally the teeth seem to be replaced every two weeks. The replaces its teeth every 8–10 days, and the  replaces its teeth about every 100 days for young sharks and about every 230 days for old shark.  Most sharks shed individual teeth, but e.g. the sheds the whole lower jaw at once. 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 to large, flat teeth adapted for crushing.

== Fossil shark teeth == === 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 and  eras, roughly about 16 to 1.5 million years ago. Its teeth on average range between 1.5 to 6.5 inch in length. The largest examples can reach a length of more than 7 inches. 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.

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 sharks disappeared relatively close to the rise of modern man, however, there have been many unconfirmed reports of large carnivorous fish resembling Megalodon sharks in recent times. Megalodon teeth have been discovered that some may argue date as recently as 10,000 to 15,000 years ago. This claim is based on the discovery of two teeth by the. 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 ===

Main Article: 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 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. == Collecting shark teeth ==

Field collecting
Locations include river bed banks, sand pits, and beaches. The most common and simplest way is to walk along the site and collect. Many people prefer to use a shovel and sieve. Many collectors use fork-like garden tools to excavate sand.

Many sites provide hard, solid teeth, that are only washed and dried. These teeth are typically worn, because they were frequently moved and redeposited in different areas repeatedly before settling down. Other locations, however, yield perfect teeth that were hardly moved during the ages. these teeth are typically fragile, and great care should be taken while excavating them.

Well known fossil hunting areas:
 * , Florida ( Sharks Tooth Festival every April )
 * , PCS Phosphate Pit, Aurora, North Carolina
 * Phosphate Pit, Lower Florida
 * , Bakersfield, California
 * , Calvert Cliffs, Maryland
 * , Morocco
 * , Khouribga, Morocco
 * , South Carolina, Florida, Georgia
 * , Antofagasta, Chile

Buying teeth
There is a small, but established shark tooth trade, and it is up to the collector if he/she wants to 'complete' their collection by buying a few fossils.

Many high quality fossils can be found online, and many are often affordable. As well as on the internet, shark teeth may be procured from Rock and Mineral shows, such as the annual, and other, smaller, rock shops.

The prices of shark teeth depend upon the overall quality of the tooth. There is no definite price for a shark tooth, as the market is based on supply-and-demand. Another way of obtaining shark teeth is to "swap" finds with others at rock shops of mineral shows/conventions.

Identification
The most often method of shark tooth identification, is to procure a book on sharks teeth and attempt to identify it yourself. Many expert collectors tend to identify their teeth this way, yet others prefer to seek experts willing to help them identify their teeth.

Many identified shark teeth are transitional species. Because sharks lose tens of thousands of teeth in their lifetime, their teeth vary greatly, because they are constantly evolving new changes in their feeding style, and their teeth.

== References ==


 * Castro, Jose (1983). The Sharks of North American Waters. College Station: Texas A&M University Press. ISBN 0-89096-143-3. 

Stevens, John D. (1987). Sharks. New York: NY Facts on File Publications. ISBN 0-8160-1800-6.
 * Hennemann RM. Sharks & Rays: Elasmobranch Guide of the World. IKAN-Unterwasserarchiv, Frankfurt, Germany 2001:266-269.