Carcharodon Megalodon: This ancient shark lived between 15 million and 25 million years ago. The ancient sharks could grow up to 50 feet in length. The carcharodon megalodon had many rows of sharp teeth. The carcharodon teeth have a single point, often with serrated edges. These teeth vary in size from small to large. The end of the tooth or root is often preserved. The fossil shark teeth are often found in phosphate mines, and sometimes in beach areas. Some teeth are found by divers. A fossil shark tooth is easy to tell from a modern day shark tooth as a fossil tooth is made of stone; the modern tooth is not.