Hydrodamalinae

Hydrodamalis is a genus of extinct herbivorous sirenian marine mammals. It included the Steller's sea cow (Hydrodamalis gigas), the Cuesta sea cow (Hydrodamalis cuestae), and the Takikawa sea cow (Hydrodamalis spissa). The fossil genus Dusisiren is regarded as the sister taxon of Hydrodamalis: together, the two genera form the dugong subfamily Hydrodamalinae. They were the largest member of the order Sirenia, whose only extant members are the dugong (Dugong dugon) and the manatees (Trichechus spp.). They reached up to in length, making the Steller's sea cow among the largest mammals other than

Dusisiren is an extinct genus of dugong related to the Steller's sea cow that lived in the North Pacific during the Neogene.

Hydrodamalinae is a recently extinct subfamily of the sirenian family Dugongidae. The Steller's sea cow (Hydrodamalis gigas) was hunted to extinction by 1768, while the genus Dusisiren is known from fossils dating from the middle Miocene to early Pliocene.