Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/98

Rh 86 P T A P T E PTARMIGAN. See GROUSE, vol. xi. p. 222. PTERODACTYLE. The extinct flying reptiles known as " pterodactyles " are among the most aberrant forms of animals, either living or extinct. Since the beginning of this century, when Blumenbach and Cuvier first described the remains of these curious creatures, they have occupied the attention of naturalists, and various opinions have been expressed as to their natural affinities. The general pro- portions of their bodies (excepting the larger head and neck) and the modification of the forelimb, to support a mem- brane for flight, remind one strongly of, the bats, but the resemblance is only superficial ; a closer inspection shows that their affinities are rather with reptiles and birds. In all pterodactyles the head, neck, and forelimb are large in proportion to the other parts of the body (fig. 1). The skull is remarkably avian, and even the teeth, which Fio. 1. Pterodactylus tpectabilis, Von Meyer, natural size, from the lithographic slate. A., humerus ; ru, radius and ulna ; me, metacarpals ; pt t pteroid bone ; 2, 3, 4, digits with claws ; 5, elongated digit for support of wing membrane : st, sternum, crest not shown ; is, ischium ; pp, prepubis. The teeth are not shown. most of them possess, and which seem so unbird-like, are paralleled in the Cretaceous toothed birds of North America. Judging from the form of the skull, the brain was small, but rounded and more like that of a bird than that of a reptile. The position of the occipital condyle, beneath and not at the back of the skull, is another char- acter pointing in the same direction. The nasal opening is not far in advance of the large orbit, and in some forms there is a lachry mo-nasal fossa between them. The pre- maxillse are large, while the maxillse are slender. In certain species the extremities of the upper and lower jaws seem to have been covered with horn, and some forms at least had bony plates around the eye. The union of the post-frontal bone with the squamosal to form a supra- temporal fossa is a reptilian character. Both jaws are usually provided with long slender teeth, but they are not always present. The vertebral column may be divided into cervical, dorsal, sacral, and caudal regions. The centra of the vertebrae are procoelous, that is, the front of each centrum is cup -like and receives the ball -like hinder ex- tremity of the vertebra next in front of it. The eight or nine cervical vertebrae are always large, and are succeeded by about fourteen or sixteen which bear ribs. Probably there are no vertebras which can be called lumbar. The sacrum consists of from three to six vertebrae. The tail is short in some genera and very long in others. The sternum has a distinct median crest, and the scapula and coracoid are also much like those of carinate birds. The humerus has a strong ridge for the attachment of the pectoral muscle, and the radius and ulna are separate bones. There are four distinct metacarpals ; passing from the inner or radial side, the first three of these bear respectively two, three, and four phalanges, the terminal ones having had Fro. 2. KJunnphorhynchus phylluntf, Marsh, from the Solenhofen slates, one- fourth natural size, with the greater part of the wing membranes preserved. x, caudal membrane ; st, sternum ; h, humerus ; sc, scapula and coracoid ; tern, wing membrane. claws. The phalanges of the outermost digit are much elongated, and except in one doubtful form are always four in number. It is the extreme elongation of this outer digit, for the support of the patagium, which is the most characteristic feature of the pterodactyle's organization. A slender bone called the "pteroid" is sometimes seen extending from the carpal region in the direction of the upper part of the humerus. Some naturalists look upon the pteroid merely as an ossification of a tendon, corre- sponding with one which is found in this position in birds, while others are inclined to regard it rather as a rudiment- ary first digit, modified to support the edge of the patagium. The pelvis is small. In form the ilia resemble rather the ornithic than the reptilian type ; but the other portions of the pelvis are more like those of the crocodiles. The hind