A crest at the back of the skull (a common feature among pterosaurs) may have functioned in species recognition; the crest of males was larger. The crest is often thought to have counterbalanced the jaws or have been necessary for steering in flight, but several pterosaurs had no crests at all. As compared with the size of the wings, the body was small (about as large as a turkey), but the hind limbs were relatively large compared with the torso. Although the limbs appear robust, the bones were completely hollow, and their walls were no thicker than about one millimetre. The shape of the bones, however, made them resistant to the aerodynamic forces of flight. Pteranodon, like other pterosaurs, was a strong flier with a large breastbone, reinforced shoulder girdles, and muscular attachments on the arm bones—all evidence of power and maneuverability. However, as in the largest present-day birds, Pteranodon's large size precluded sustained beating of the wings, so it most likely soared more than it flapped. The eyes were relatively large, and the animal may have relied heavily upon sight as it searched for food above the sea.