\Ich`thy*o*sau"rus\, n.; pl. {Ichthyosauri}. [NL.,
fr. Gr. 'ichqy`s, -y`os, a fish + say^ros a lizard.]
(Paleon.)
An extinct genus of marine reptiles; -- so named from their
short, biconcave vertebr[ae], resembling those of fishes.
Several species, varying in length from ten to thirty feet,
are known from the Liassic, O["o]litic, and Cretaceous
formations.