Steller's sea cow
Steller's sea cow was a member of the genus "Hydrodamalis", a group of large sirenians, whose sister taxon was "Dusisiren". Like those of Steller's sea cow, the ancestors of "Dusisiren" lived in tropical mangroves before adapting to the cold climates of the North Pacific. "Hydrodamalis" and "Dusisiren" are classified together in the subfamily Hydrodamalinae, which diverged from other sirenians around 4 to 8 mya. Steller's sea cow is a member of the family Dugongidae, the sole surviving member of which, and thus Steller's sea cow's closest living relative, is the dugong ("Dugong dugon").