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 rare, tiger ragged-tooth shark, photographed off the coast of Columbia. Scientists attribute this remarkable longevity to the shark's superior physiological developments.