pterodactyl - a flying dinosaur, now extinct. The wing was a membrane supported by the bony skeleton of the arm, forearm, and hand

bird - the bones of the hand support the primary feathers and the bones of the forearm support the secondaries. A small alula is supported in the 'thumb' position

bat - an elastic membrane is supported by the skeletal elements. The long slender digits are distinctive

human - forelimb skeleton for comparison