In their maximum and final development the pterodactyls attained the highest volant powers of all creatures, whether of the past or present, being quite incapable of locomotion except in the air. Pteranodon with a wing expanse of 22 or more feet, had a body smaller than that of a turkey. Nyctosaurus, an allied genus from Kansas, with a body only six inches long and five or six inches across the shoulders, meas ured eight feet from tip to tip of expanded fingers, and probably did not weigh more than five pounds when alive. They doubtless spent most of their time in the air, resting suspended from cliffs by their small clawed fingers, much like the way of bats, except that their fingers, instead of their toes, are used for suspension. The presence of bony plates in the sclerotic membranes of the eyes indicates either nocturnal or soaring habits. (Cf. Fig. 2).
In flight, unlike birds and bats, their served more as gliding surfaces, and could have been used only for upward and downward mo tion. Flight was controlled by the legs, which were extended backward and connected by membrane, serving the purpose of the feathered tail in birds. The rudder-tailed Rhamphor hynchus (Fig. 1) was a veritable monoplane.
Their food habits are only imperfectly known. Because so many of their remains are found in ocean deposits, it is believed that they fed largely upon fishes, and this assumption is strengthened by the discovery, in several instances, of the remains of their stomach con tents containing comminuted fish-bones. But it is probable that they also lived in part upon other flying creatures, insects and small birds, which must have been swallowed whole. Their brain was better developed than in other rep tiles, and because of this and of the highly developed, pneumatic skeleton, it has been thought by some that they were warm blooded; they have even been placed in a separate class of back-boned animals. They were, however,
true reptiles, even though warm-blooded, which may have been possible.
Remains of young pterodactyls have never been found. Like most reptiles they were prob ably oviparous, since otherwise, among the many hundreds of known specimens, embryonic young would probably have been found. The bones of the pelvis, unlike those of birds, were closely connected, and only eggs of small size could have passed through it, not much larger young were cared for by the parents until able to care for themselves. These facts suggest limited breeding grounds, and extensive seasonal migration. (Note Fig. 3).
About a dozen genera are defined, of which Rhamphorhynehns, Dimorphodon, Pterodactv lus, Pteranodon and Nyctosaurns are best known. In North America, with the exception than hens' eggs, even in the largest kinds. Such small young would have been practically helpless, which, together with the greater intel ligence of the adult animals, as indicated by their large brains, renders it probable that the of some fragmentary remains from the upper most Jurassic, Pteranodon and Nyctosanrus are the only, though abundantly represented genera. • Bibliography.— Cuvier first named this group. Consult the °Ossemens Fossile,* (1809 and 1824). Also consult Buckland's Bridge water Treatises, 1837. Later works are H. G. Seeley's