ANN ARBOR—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. Common as such interactions may be, it’s often difficult to trace their origins back in evolutionary time. Now, a … Continue reading Urged on by urchins: How sea lilies got their get-up-and-go