Sharks are surely one of the most fearsome creatures on Earth. But they are also one of the most sophisticated and enduring. The oldest shark fossils date from more than 300 million years ago, before the age of the dinosaurs. And a few existing shark species, such as the hornshark, have kept the same basic physical characteristics for more than 150 million years.

a tiger ragged-tooth shark
Photo courtesy Carl Roessler
A rare, tiger ragged-tooth shark, photographed off the coast of Colombia. See more pictures of sharks.

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What do you know about the fish at the apex of the ocean's food chain? Check out this quiz from Animal Planet:

Into the Jaws Quiz

Scientists attribute this remarkable longevity to the shark's superior physiological developments. Sharks are outfitted with several special characteristics that make them highly effective, both as hunters and survivors. In this article, we'll examine these unique qualities to see why the shark is top dog in the ocean.

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