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Fossil Shark Tooth Diving Identification Guide

Fossil shark teeth are common and are the only parts of these fish usually preserved, as the softer bodies decay. Learning to identify the teeth can lead to a greater appreciation of ancient sharks' living relatives: some are endangered, and organizations such as the Shark Trust detail endangered species. Although some natural history guidebooks and charts are waterproof and can be taken underwater for use during a dive, these are mainly to help identify living creatures. Use prior information as a guide for basic fossil tooth identification while diving. To make the most of your dive time, save detailed identification for after the dive, when you can look at any collected specimens more closely, clean them if you want to and compare them, or fossil teeth you memember from your dive, to a clearly illustrated, published chart or book.

What to Look For
- Look carefully along the sea bed for differences in shape, size and color, especially anything dark or dark and shiny, which might turn out to be a fossil shark tooth. The fossils might be partially hidden or lying at an angle, so the whole side outline as usually seen in photos may not be visible. This kind of observation is a skill that may need time to develop. Churning up sand and particulates from the sea bed will reduce visibility, so move carefully if you are feeling along the sea floor.
Fossil Teeth or Modern?
- Visibility when fossil-hunting underwater may not always be this clear.
  
  Look at the color. Generally, the root and crown of a modern shark tooth will be white or near-white in color. By contrast, a fossil shark tooth will usually be a dark color, most commonly dark gray. The color change is due to the fossilisation process. The actual color of a fossil shark tooth depends on the color of the sediment in which it has been preserved, so it is not a useful factor in further identification.
Tooth Shape
- Use the following descriptions as a basic identification guide while diving. A shark family may include more than one genus, and a genus may include several species. For practicality underwater, several general descriptions of teeth from sharks of different families are included. Size can vary according to the original location of the tooth within the mouth.
  
  Megatooth Sharks (family Otodontidae, genus Carcharodes): Single, chunky, pointed crown (point is slightly rounded, compared to other teeth). Symmetrical to slightly asymmetrical crown, which may have cusps at the side (depending on the species). Crown has regular serrations. Size varies from a few cm to a greater than 17 cm height of crown. The largest belong to the huge Megalodon shark species and are the largest shark teeth found.
  
  White Sharks (family Lamnidae, genus Carcharodon): Single, long, slim, pointed crown with a definite slant to one side. Crown has smooth or irregular serrations. Distinctly arched root. Often distinct striations from root towards tip of crown. Includes the Great White (species Carcharion).
  
  Lemon Sharks (family Carcharhinidae, genus Negaprion): Single, long, slim, pointed crown, slightly curved. Crown is smooth. Root slightly arched.
  
  Tiger Shark (family Carcharhinidae, genus Galeocerdo): Single, triangular, distinctly asymmetrical, pointed crown (point juts to one side part way up the crown), with sharp point. Crown may be slightly twisted. Serrations on both edges--coarser on one side, fine on the other. Distinctly arched root.
  
  Gray Sharks (family Carcharhinidae, genus Carcharinus): Single, triangular, asymmetrical crown (point juts in a less angular manner to one side, compared to Tiger Shark teeth), with sharp point. Crown is flattened slightly. Crown is serrated (less strongly than Tiger shark teeth). Slightly curved root.
  
  Cow shark (family Hexanchidae): Each tooth includes several cusps, each cusp like a small, pointed crown. Up to 12 cusps on one tooth (depending on the species), decreasing in size. Serrations at base of largest cusp. Root is rectangular.
  
  For more detailed identification, to the species level, or if you have found a tooth of a different shape, use a pictorial printed guide when you have returned to dry land and can inspect the fine details of the teeth collected
Difficulties
- Living sharks lose and renew their teeth continually throughout their lives
  
  Some specimens may be difficult to identify. Pathogenic teeth have grown with irregularities, such as bits missing (cusps, serrations), misshapen edges or twisted crowns. In addition, differences can occur between the teeth of males and females of the same species. In a single shark, teeth may also vary depending on which part of the jaw they occupy and may even vary throughout the lifetime of the shark (reflecting changes such as in environment or diet). Any irregularities will have been preserved in fossil teeth. Other teeth may be damaged or broken after preservation.
  
  If you can identify the species, you might be able to look up further information about the original shark, such as its likely size and diet, which may not be what you expect. Some present-day sharks live on invertebrates rather than large animals.

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