Class Mammalia Linnaeus, 1758 - mammals Subclass Theria Parker & Haswell, 1897 Order Sirenia Gill, 1872 - sea cows Family Dugongidae Gray, 1821 - dugong and sea cow Subfamily ‡Hydrodamalinae Palmer, 1895 Genus ‡Hydrodamalis Retzius, 1794 - Steller's sea cow, great northern sea cow 1 ‡Hydrodamalis gigas (Zimmermann, 1780) - Steller's sea cow