The Biggest Shark  Teeth Reveal

That Ever Lived, Fossil

The giant shark that lived

 more than 23 million years ago was almost four times bigger than the great white shark that cruises our oceans today.

However, the two

 shark species, which once coexisted, likely hunted some of the same prey.

This competition could potentially

 have been one reason why the 65-foot-long (20-meter-long) megalodon went extinct

Researchers analyzed dietary signatures

 contained in the teeth of 13 extinct shark species and 20 modern sharks to understand where they fit in the food chain

The researchers were able

 glean this information by looking at the presence of different isotopes, or variants

Chemical element zinc

 preserved in the sharks' tooth enamel. Zinc is essential for living organisms

Hueter Told CNN That Ocearch

Has tagged great white sharks as long as 17.5 feet and as heavy as 4,000 pounds, meaning Ironbound is of modest size.