The “winged reptiles” of the Mesozoic Era, constituting the closest major group to Dinosauria and sharing many features with them. Their common ancestor was a small, bipedal, agile archosaur reptile probably similar to the small Scleromochlus of the Late Triassic. This ancestor probably possessed a large, lightly built skull, a short body, long hindlimbs, and digitigrade feet with four long metatarsals. Pterosaurs inherited all these features, and they further evolved the power of flight. Bats have a wing of skin stretched among four fingers and extending from the arms to the legs (and often the tail), and birds have a wing of feathers supported by the arm and the fused wrist–hand bones. Pterosaurs had a wing of skin that was internally supported by long, fine, possibly keratinous stiffening fibers and braced by the forelimb, including a greatly elongated fourth finger (the first three fingers remained small). Their brains were relatively large and somewhat birdlike; the canals of the ear region show that they were well suited for life in the air.