<P> In taxonomy, shark teeth are counted as follows: rows of teeth are counted along the line of the jaw, while series of teeth are counted from the front of the jaw inward . A single tooth row includes one or more functional teeth at the front of the jaw, and multiple replacement teeth behind this . For example, the jaws of a bull shark can have 50 rows of teeth in 7 series, with the outermost series functional, but most sharks have 5 series with the average shark having about 15 rows of teeth in each jaw . The small teeth at the symphysis, where the two halves of the jaw meet, are usually counted separately from the main teeth on either side . Sharks are also known to lose at least one tooth per week . Due to their specific arrangement of rows and series however, lost teeth can be replaced within a day . </P> <P> Identification of most sharks are found through a combination of tooth counts and tooth shapes . Teeth can even lead to the identification of shark species like the requiem shark . The fossilized records of teeth helps illustrate evolutionary history, and isolated teeth are used to study and analyze specific linear measurements of the species . In order to identify teeth and specific information about the teeth, research can be done on a shark tooth . This research may uncover many different aspects about the tooth itself, and the shark species . This proves complicated, however, due to the fact that most fossilized teeth are found mixed and scattered . To collect information on basic - life history and get dispersal estimates of a shark tooth, molecular - based technology is very efficient . To further shark population studies, collection of mtDNA can be extracted from shark jaws and teeth . To study the caries - reducing effect in sharks, studies are done on the fluorine atoms that are bound covalently to calcium atoms in the teeth . Each tooth has a complex fluorapatite structure enameloid . In order to reduce effects of deterioration in the teeth, it is useful to sample only the surface of the enameloid of the tooth for this specific research . Studying and researching shark teeth betters our understandings of shark feeding behaviors, evolutionary changes, and mechanisms . This helps us to identify the teeth, and even the species . </P> <P> The oldest known records of fossilized shark teeth are by Pliny the Elder, who believed that these triangular objects fell from the sky during lunar eclipses . </P> <P> According to Renaissance accounts, large, triangular fossil teeth often found embedded in rocky formations were believed to be petrified tongues of dragons and snakes and so were referred to as "tongue stones" or "glossopetrae". Glossopetrae were commonly thought to be a remedy or cure for various poisons and toxins; they were used in the treatment of snake bites . Due to this ingrained belief, many noblemen and royalty wore these "tongue stones" as pendants or kept them in their pockets as good - luck charms . </P>

How many teeth do sharks have in their lifetime