Sharks are majestic predators of the deep that have fascinated the masses for time untold. Believe me, I am hooked on finding out more about them. That being said I am by no means a paleontologist, but I have done a decent amount of research to increase my knowledge on the subject of finding shark teeth and answering the 5 W's (who, what, when, where and why) about shark teeth. Here are some answers to many frequently asked questions regarding shark teeth.



Who do the teeth belong to?



The shark teeth that we are finding and collecting are not the sparkling white teeth you would extract from a modern living shark, but beautiful, glossy black or brown fossilized teeth of their ancient ancestors. These teeth are 10,000 years and older and have been hardened with the test of time. As a whole Shark teeth have changed very little over the years with very few differences between the different geological eras and periods. This makes identifying the age of the teeth hard to do without knowledge of where they had been found.



What species did the teeth come from?



Identifying the species of shark that a particular tooth came from can be tedious, but fun. There are dichotomous keys, diagrams, and guides written to help to determine which tooth belongs to which shark. Some of these quick reference guides may also give a rough estimate of age, but it is just an estimate. Most are written based on the physical descriptions of the tooth, but the geological era and/or period are also important key factors in determining the specific species and age bracket. Some guides are written for specific search areas for just this reason. Pictured above are a couple of the guides I use to identify teeth in my collection.



When were these teeth deposited? How old are the teeth I find?



The easiest way to find out how old the teeth are is to look at the sediment layers where they were found. Above are the geological sediment maps of Florida. One is the whole state, and the second is of the northeast area where I focus my searching. A Google search for geological sediment map of your area will provide you with a map. Note: Sharks themselves are not very good indicators of age, because shark evolution as a whole is a slow process. Many of the species found in today's oceans have been around for millions of years. A better indicator, if geological maps are not available, are other fossils fond in the area such as invertebrates, reptiles, mammals, and birds. But that would require you to find the other fossils, do more research to determine the species as well as their geological age, and then compare the information to the shark fossil record for the area. Maps are WAY easier.



Why are there so many fossilized teeth?



The first reason there are so many fossilized teeth is that there are simply so many shark teeth, it’s bound to be one of the most common fossils. The reason for all those shark teeth is that sharks have multiple rows of teeth that are constantly being shed to maintain their razor sharp bite. EACH individual shark can shed more than 30,000 teeth in its lifetime. Multiply that 30,000+ teeth by every shark of every species that has ever lived over the past tens of millions of years, and you get a staggering amount of teeth that can be fossilized! Of course, not every tooth is lucky enough to fall to the seafloor and be swiftly buried in the sediment. Those teeth that are not lucky enough to be safely ensconced in the sediment will be broken down by either weathering/abrasion or decay from oxidation and bacteria. This leads to the second reason there are so many teeth. The teeth are made of dentin, which is harder and denser than bone. This allows more time for the teeth to be protected in the sediment before eroding away. Those teeth that were sheltered in the sediment slowly became fossilized over several thousand years. These are the teeth that are found along beaches, in muddy stream beds, and buried within sedimentary rock.





Why are these teeth black?



Since these teeth are fossilized, they no longer look like teeth freshly extracted from a living shark's mouth. The color of the fossilized teeth is dependent upon the minerals that were present when the tooth was lost. As the teeth would settle into the surrounding sediments and permineralization would occur. Water would seep through sediments picking up minerals before flowing over the teeth. Those minerals would then be deposited into the porous structure of the teeth, forming a fossil. Colors of teeth will vary based on the minerals deposited in the teeth and how they react with trace amounts of oxygen.



Why do we find mostly teeth and not much more of the shark?



Sharks are cartilaginous fish, meaning that most of their skeleton is cartilage rather than bone. Cartilage does not mineralize as well as bone and therefore breaks down faster than bone. This makes it much harder for cartilage to fossilize. For this reason, There are very few fossilized skeletons of sharks, but they do exist. The denser the cartilage was, the more likely it was to be fossilized. Examples of other shark fossils are the shark's vertebrae, jaws, dermal ossicles, fin spikes, rostal nodes, and even feces (or coprolites)! Later in this Instructable you will see what fossilized feces and vertebrae look like.



Where are fossils found?



Fossils can be found in sedimentary rocks or unconsolidated sediments, which are loose materials ranging from clay to sand to gravel. In Florida, many of these sediments have not been around nearly long enough to compress into solid (sedimentary) rock, so they are still loosely packed. Sea levels were much higher in the past and what is now Florida was once covered by sea water. Sharks inhabited those waters and subsequently deposited large amounts of teeth there. The teeth settled into the sea bottom, and the fossilization process started. Later, changes in climates caused the sea levels to fall, exposing the sea floor and creating what we now call Florida. The unconsolidated sediments that were originally deposited on the sea floor long ago may now be exposed. Within those exposed sediments or sedimentary rocks, lay the fossilized shark teeth found today. This sedimentary layer can easily be located on beaches in most of Florida. Also knowing where specific sediments are based on age will help pinpoint the areas to start exploring. The geological map of Florida is a great reference to locate this information.





Where can you find out more?



Please check out these very well written and informative webpages!



Sources:



http://www.flmnh.ufl.edu/vertpaleo/fossilspeciesho...



http://www.flmnh.ufl.edu/vertpaleo/fossilspeciesCa...



http://www.fossilguy.com/gallery/vert/fish-shark/r...



http://www.fossilguy.com/topics/shark-teeth-colors...



http://paleobiology.si.edu



http://ocean.si.edu/sharks

