Nyctosaurus

Nyctosaurus is a genus of pterodactyloid pterosaur notable for its extraordinarily large cranial crest, otherwise known only in the distantly related tapejarids. Its remains have been found primarily in the mid-western United States, which during the late Cretaceous Period was covered in an extensive shallow sea.

Nyctosaurus is the only pterosaur to have lost its clawed "fingers", with the exception of the wing finger, which is likely to have impaired its movement on the ground, leading scientists to conjecture that it spent almost all of its time on the wing and rarely landed. In particular the lack of claws with which to grip surfaces would have made climbing, or clinging to cliffs or treetrunks, impossible for Nyctosaurus. Nyctosaurus appears to have outlasted its relative Pteranodon and may have survived until the great extinction 65 million years ago.

Crest
Early fossils of Nyctosaurus did not reveal an elaborate crest, only a smaller structure similar to the crest of the closely related Pteranodon.

A few scientists hypothesize that this crest, which resembles an enormous antler, may have supported a skin "headsail" used for stability in flight. While there is no fossil evidence for such a sail, studies have shown that a membranous attachment to the bony crest would have imparted aerodynamic advantages.