Dugongidae

The dugong (; Dugong dugon) is a 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.

Dugongidae is a family in the order of Sirenia. The family has one surviving species, the dugong (Dugong dugon), one recently extinct species, Steller's sea cow (Hydrodamalis gigas), and a number of extinct genera known from fossil records. thumb|Dugong skeleton displayed at Philippine National Museum

Metaxytherium is an extinct genus of dugong that lived from the Oligocene until the end of the Pliocene. Fossil remains have been found in Africa, Europe, North America and South America. Generally marine seagrass specialists, they inhabited the warm and shallow waters of the Paratethys, Mediterranean, Caribbean Sea and Pacific coastline. American species of Metaxytherium are considered to be ancestral to the North Pacific family Hydrodamalinae, which includes the giant Steller's sea cow.

Halitherium is a dubious genus of extinct dugongid sea cow that arose in the late Eocene, then became extinct during the early Oligocene. Its fossils are common in European shales. Inside its flippers were finger bones that did not stick out. Halitherium also had the remnants of back legs, which did not show externally. However, it did have a basic femur, joined to a reduced pelvis. Halitherium also had elongated ribs, presumably to increase lung capacity to provide fine control of buoyancy.

Rytiodus (meaning Rytina, "wrinkled", an old name for Steller's sea cow) is an extinct genus of sirenian, whose fossils have been discovered in France, Europe and Libya.

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.

Bharatisiren is an extinct genus of mammal which existed in what is now India during the early Miocene (Aquitanian) period.

Dioplotherium is an extinct genus of sirenian related to the dugongs, known from Neogene-aged deposits from southern North America.

Nanosiren garciae is an extinct sirenian dugong that lived in warm shallow seas in what is now Venezuela, approximately 11.610—3.6 Ma during the Miocene and Pliocene. The species is listed in the Paleobiology Database, funded by the Australian Research Council.

Caribosiren is an extinct genus of afrotherian mammal which existed in what is now Puerto Rico during the Chattian stage of the Oligocene epoch. Fossils have been recovered from the San Sebastián Limestone.

Corystosiren is an extinct genus of dugongid sirenian mammal which existed in the waters of the Caribbean Basin during the Early Pliocene. Fossils have been found in the Yucatán Peninsula, Mexico, and Florida.