The megabat family contains the largest bat species, with individuals of some species weighing up to 1.45 kg (3.2 lb) and having wingspans up to 1.7 m (5.6 ft). Not all megabats are large-bodied; nearly a third of all species weigh less than 50 g (1.8 oz). They can be differentiated from other bats due to their dog-like faces, clawed second digits, and reduced uropatagium. Only members of one genus, Notopteris, have tails. Megabats have several adaptations for flight, including rapid oxygen consumption, the ability to sustain heart rates of more than 700 beats per minute, and large lung volumes.