‖n. pl. [ NL. See Ichthyosaurus. ] (Paleon.) An extinct order of marine reptiles, including Ichthyosaurus and allied forms; -- called also Ichthyopterygia. They have not been found later than the Cretaceous period. [ 1913 Webster ]
a. (Paleon.) Of or pertaining to the Ichthyosauria. -- n. One of the Ichthyosauria. [ 1913 Webster ]