Halitherium also had elongated ribs, presumably to increase lung capacity to provide fine control of buoyancy.

Halitherium is the type genus of the subfamily Halitheriinae, which includes the well-known genera Eosiren and Eotheroides and lived from the Eocene to the Oligocene.

[2] It was originally coined by Johann Jakob Kaup on the basis of a premolar from the early Oligocene (Rupelian) of southern Germany, but Kaup himself mistakenly stated that the premolar, in his opinion, gehort zu Hippopotamus dubius Cuv., unaware that H. dubius is actually a junior synonym of the primitive sirenian Protosiren minima, while simultaneously coining the genus and species name Pugmeodon schinzii for the same specimen.

[3] For his part, the renowned German paleontologist Christian Erich Hermann von Meyer included the type specimen of Halitherium schinzii in his composite species Halianassa studeri,[4] whose hypodigm also included the type specimens of Metaxytherium medium and Protosiren minima as well as a Miocene-age maxilla and a skeleton from the molasse basin in Switzerland.

Voss based the opinion on the type species, H. schinzii, being nomen dubium, with its holotype fossil, an isolated molar, having no diagnostic value.