Mariah RossPeriod 8Teeth Adaptation Among SharksShark teeth often change size and shape based on its location in the shark's mouth, whether from the upper or lower jaw, and age , by the sex and species of the shark it comes from. Shark teeth are produced and fall in series as they move forward as if on a conveyor belt. With this replacement system, a shark can produce, use and lose up to 6,000 teeth each year. If a shark tooth is well preserved it offers the scientist a number of points that can be used to identify the species and basic taxonomic group of the shark from which it came. However, large numbers of shark tooth fossils are not well preserved and are often worn to the point of becoming smooth and shapeless, making them almost useless in the identification process. The first fossil shark teeth and subsequent evolution The first known fossil shark teeth are those of Leonodos (left) dating back to around 400 million years ago. Their overall crown shape vaguely resembles that of fossilized Xenacanthus teeth (right), perhaps indicating that these early sharks were related. Their roots, however, are quite different, suggesting that Leonodus and Xenacanthus may have developed similar crowns as an adaptation to feeding on similar prey rather than due to shared ancestry. No one is sure which group of sharks evolved into their modern counterparts, but until recently many scientists believed they were the Hybodonts. However, paleoichthyologist John G. Maisey's extensive studies of fossil and modern sharks lead to the belief that hybodonts were a side branch of shark evolution that did not give rise to any group of modern sharks. Maisey proposed that a genus known as Synechodus may be more closely related to... half of the paper ark that can eat 1% to 10% of its overall body weight per week. Many shark species swallow their food whole without any form of chewing. While some sharks probably aren't very selective eaters, some eat some foods more than others. For example, hammerhead sharks are known to eat rays; bull sharks eat other sharks; and dogfish eat crabs and lobsters. Tiger sharks feed opportunistically on both live food and carrion. Their prey includes bony fish, other sharks, marine mammals, seabirds and invertebrates. How Sharks Work by Tom Harris, http://animals.howstuffworks.com/fish/sharks/shark4.htmMartin, R. Aidan. 2003. Copyright and Usage Policy. Publication on the World Wide Web, www.elasmo-research.org/copyright.htm http://seaworld.org/en/animal-info/animal-infobooks/sharks-and-rays/diet-and-eating-habits/ NONE AUTHOR LISTED, DIET AND EATING HABITS