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.