Claim: Bats are the only mammals naturally capable of true and sustained flight.
Evidence: Bats are mammals of the order Chiroptera -LRB- -LSB- kaɪˈrɒptərə -RSB- from the χείρ - cheir , `` hand '' and πτερόν - pteron , `` wing '' -RRB- whose forelimbs form webbed wings , making them the only mammals naturally capable of true and sustained flight.