Ichthyosauria \Ich`thy*o*sau"ri*a\, 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.

Source: Webster's Revised Unabridged Dictionary (1913)