• Ichthyologist-scientists who study sharks.
•  Fauna-the animals given region or peroid considered as a whole. 
• Chondrichthyian-sharks and relatives. 
• Carcharodon megalodon-giant fossil tooth. 
• Cladoselache-another giant fossil tooth. 
• Stethacanthus-another giant fossil tooth. 
• Silurian-the late periods, about 500 million years ago. 
• Ordovician-the late periods, about 500 million years ago.

  For more information about sharks, go to the Shark Dictionary on Enchanted Learning