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April 18, 2012
Predator pressure
A U-M paleontologist and his colleagues have found an example of a one-sided, asymmetrical predator-prey relationship. Over a nearly 200-million-year span, sea urchins (the white predator at right) have forced formerly stationary marine animals called crinoids (the red prey at left) to develop the ability to escape from them by creeping along the ocean floor.