Dugongidae

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.
 Dugongidae's body weight ranges from 217 to 307 kg for juveniles, 334 to 424 kg for subadults, and 435 to 568.5 kg for adults. Oral temperatures for individual dugongs is determined from 24° to 34.2 °C. Heart rate readings are from 40 to 96 bpm and vary between individual dugongs. Respiration rate during the out-of-water phase is from 1 to 33.
Taxonomy.
The genera "Eosiren", "Eotheroides", and "Prototherium" have been assigned to Halitheriinae in the past, but recent cladistic analysis recovers these genera as basal to the clade formed by Trichechidae and Dugongidae. Moreover, Halitheriinae is paraphyletic with respect to Dugonginae and Hydrodamalinae, and further use of the name should be discontinued because the type genus is based on a non-diagnostic tooth.