"pertaining to or situated near a tail," 1660s, from Latin cauda "tail of an animal," which is of unknown origin, + -al (1).

giant sea reptile from the Mesozoic, 1868, from Modern Latin (coined by E.D. Cope), from Greek elasmos "metal plate" (from elan "to strike;" see elastic) + -saurus. So called from the caudal laminae and the great plate-bones.