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. The dugong is the only strictly
marine herbivorous mammal.