Wyvern

A distant cousin to the true dragons, the wyvern is a huge flying lizard with a poisonous stinger in its tail. A wyvern’s body is 15 feet long, and dark brown to gray; half that length is tail. Its wingspan is about 20 feet. A wyvern weighs about one ton. They are built more like bats than lizards, having two legs and two wings; contrast this with true dragons, which have four legs and two wings.
  Wyverns are of animal intelligence, but are excellent predators with good hunting abilities. When attacking they will make a loud hiss, or sometimes a deep-throated growl much like that of a bull alligator.
  Wyverns attack nearly anything that isn’t obviously more powerful than themselves. A wyvern dives from the air, clawing at its opponent with its talons and stinging it to death.