Urged on by urchins: How sea lilies got their get-up-and-go

[Harlequinmania]

Nature abounds with examples of evolutionary arms races. Certain marine snails, for example, evolved thick shells and spines to avoid be eaten, but crabs and fish foiled the snails by developing shell-crushing claws and jaws. Now, a study finds that sea urchins have been preying on marine animals known as crinoids for more than 200 million years and suggests that such interactions drove one type of crinoid -- the sea lily -- to develop the ability to escape by creeping along the ocean floor.

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