Class [Mammalia] Linnaeus, 1758 - mammals Order Sirenia Gill, 1872 - sea cows Family Dugongidae Gray, 1821 - dugong and sea cow Genus ‡Hydrodamalis Retzius, 1794 - Steller's sea cow, great northern sea cow ‡Hydrodamalis gigas (Zimmermann, 1780) - Steller's sea cow