Your request was ichtyosaurus which is probably a typo from ichthyosaurus.
ichtyosaurus -
Traditional English :: ichthyosaurus
ichtyosaurus - n. (also ichthyosaur) any extinct marine reptile of the order Ichthyosauria, with long head, tapering body, four flippers, and usu. a large tail. [ICHTHYO- + Gk sauros lizard]