ステラーカイギュウ
The dugong (; "Dugong dugon") is a medium-sized marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest modern relative, Steller's sea cow ("Hydrodamalis gigas"), was hunted to extinction in the 18th century.