| Noun | 1. | genus Hydrodamalis - a genus of the family Dugongidae comprising only Steller's sea cow mammal genus - a genus of mammals Dugongidae, family Dugongidae - a family of mammals of order Sirenia including dugongs and Steller's sea cow Hydrodamalis gigas, Steller's sea cow - extinct large sirenian mammal formerly found near the Asiatic coast of the Bering Sea |