Gunakadeit is an extinct genus of thalattosaur. It is known from a single species, Gunakadeit joseeae, which is based on an articulated and mostly complete skeleton from the late Triassic (middle Norian) Hound Island Volcanics of Alaska. Gunakadeit possessed a variety of features from the two major suborders of thalattosaurs, Askeptosauroidea and Thalattosauroidea, and it is considered the most basal member of the latter group. Despite this, it is also the youngest known thalattosaur genus, with the group going extinct at the end of the Triassic. Gunakadeit's basal position and relatively recent occurrence implies a 20-million-year ghost lineage connecting it to the rest of Thalattosauria. The skull ends in a sharply pointed and toothless tip like the askeptosauroid Endennasaurus, but unlike Endennasaurus, Gunakadeit had poorly developed joints and was likely exclusively aquatic in behavior.
