http://www.oceanicresearch.org/education/wonders/sharks.html http://www.oceanicresearch.org/education/wonders/sharks.html http://www.oceanicresearch.org/education/wonders/sharks.html http://www.oceanicresearch.org/education/wonders/sharks.html http://www.oceanicresearch.org/education/wonders/sharks.html Sharks: Predators with a Purpose 300 million years Oceanic Research Group: Sharks http://www.oceanicresearch.org/education/wonders/sharks.html http://www.oceanicresearch.org/education/wonders/sharks.html