Dallasaurus

Dallasaurus ("Dallas lizard") is a basal mosasauroid from the Upper Cretaceous of North America. Along with Russellosaurus, Dallasaurus is one of the two oldest mosasauroid taxa currently known from North America. This small semi-aquatic lizard measured less than a meter in length, compared to such gigantic derived mosasaurs as Tylosaurus and Mosasaurus, each exceeding 14 meters.