AMHERST, Mass. - University of Massachusetts biologists have led a team that has determined how some stingrays, despite having skeletons made of cartilage, are able to crush hard-shelled prey such as mollusks and snails. This is the first time that scientists have found, within the cartilage skeleton of a modern animal, rigid support structures made of minerals; such structures had previously been found only in fossils of ancient sharks. Details will be published in the Oct. 1 issue of the journal Nature. UMass graduate student Adam Summers is the main author, along with assistant professor Elizabeth Brainerd, and Thomas Koob of Shriners Hospital for Children in Tampa, Fla.