Order PTEROSAURI.
Sub-Order 1. Pterodactyli, with alveolar teeth in the upper and lower jaws. Imperfect remains, impressions of phalanges of the long patagial finger, are known from the Rhaetic of Würtemberg. The oldest well-known genus is Dimorphodon, Lower Lias of Lyme Regis. D. macronyx.–Total length between 3 and 4 feet, of which the large light skull takes up about 9 inches, and the long thin tail about 2 feet. The patagial finger is about 20 inches, the whole wing about 28 inches long. Rhamphorhynchus longicaudatus of the Upper Oolite of Germany is remarkable for the long slender teeth, which are directed forwards and separated by wide spaces from each other. The nine or ten cervical vertebrae are elongated. R. phyllurus of the same geological age has left impressions of the flying membranes. They extend from the whole length of the wing and the sides of the trunk to the thigh as far as the knee, and from the inside of the hind-limbs to the tail. The end of the tail carries a spatulate membrane. Allied is Ornithocheirus, with many species in the English Wealden and Greensand. Pterodactylus, with many species from the Upper Oolite, chiefly of Germany.–The tail is very short, consisting of a few vertebrae only. The seven neck-vertebrae are so much elongated that the neck is as long as the trunk with the tail. P. longirostris measures about 1 foot in total length, while P. spectabilis is one of the smallest, only of the size of a lark. The wings, however, measure 10 inches from tip to tip. The largest is P. giganteus, with a "spread" of more than 5 feet.
Sub-Order 2. Pteranodontes.–The beak is long, pointed, toothless, and laterally compressed; mandibular symphysis very long. Pteranodon longiceps.–The skull has a long parieto-supraoccipital crest, which extends far back. The supratemporal foramina are abolished. The pre-orbital and orbital foramina are confluent. The scapulae are attached to several thoracic vertebrae. The skull of this gigantic species has a length of two feet and a half, and the spread of the wings measures nearly 20 feet. This, and several much smaller species, are from the Middle Cretaceous formation of Kansas.
Fig. 117.–Rhamphorhynchus muensteri, × ⅐, as restored by Marsh. (From Geikie.)
Sub-Class X.–PYTHONOMORPHA.
Very long-necked and long-bodied marine Cretaceous reptiles, with movable quadrates, single lateral temporal arches and procoelous vertebrae; with paddle-shaped, pentadactyle limbs; and with the teeth ankylosed to the jaws.
The skull possesses many of the essential features of the typical lizards. The premaxillaries, frontals, and parietals are fused into unpaired bones. There is an interparietal foramen. The nostrils are dorsal, bordered by the premaxillae, nasals, prefrontals, and maxillaries. The quadrato-jugal arch is incomplete, and the orbit is posteriorly confluent with the infratemporal fossa, but a supratemporal space is shut off by the single arch, which is composed of the postfrontal, squamosal, and supratemporal. The latter is interposed between, and connects the squamosal and quadrate with the latero-posterior branch of the parietal. There is a space between this parieto-squamosal arcade and the epi-otic, which is fused with the lateral wing of the lateral occipital bone. The foramen magnum is bordered by the two supra-occipital, lateral occipital, and the unpaired basioccipital bones; the condyle is triple. The quadrate is movable, articulating with the squamosal and laterally expanded epi-otic. There is no bony connexion of the quadrate with the jugal, which is restricted to its anterior half, and attached to the maxillary and lacrymal. The quadrato-jugal is absent as a separate bone; it is probably fused with the anterior surface of the quadrate, as indicated by a perforation of the quadrate, resembling in this respect the Rhynchocephalia. The vomers are long, and separate the elongated choanae from each other. The palatines separate the vomers from the pterygoids, which enclose a long median vacuity and are not connected with the quadrates. The teeth are conical, and stand near the inner margin of the jaws upon little prominences, with which they fuse. Some genera have teeth upon the pterygoids also.
The vertebrae are very numerous and are mostly procoelous. They are noteworthy for the possession of an additional anterior and a posterior pair of articulating processes on the neural arches, homologous with the zygosphenes and zygantra of Snakes and Iguanidae (see p. [582]). Intercentra are absent, except in the tail. The ribs have no tubercula, and articulate with the centra of the vertebrae to which they belong.
The pectoral arch is strong. The scapulae are short and broad; the coracoids, fused with the precoracoids, except for a notch, are flat and broad, and meet ventrally; posteriorly they articulate upon the anterior margin of the flat sternum, to the lateral margin of which are attached several ribs. Clavicles and interclavicle seem to be absent. Abdominal ribs are likewise absent. The pelvic girdle is feeble; the ilia, ischia, and pubes are loosely connected with each other, the pairs of ventral elements meeting also in the middle line. The ilia are loosely attached to two vertebrae in the Dolichosauri; in the Mosasauri they have lost this connexion. Both anterior and posterior limbs are transformed into pentadactyle paddles, with much shortened and broadened bones of the arms and legs. The digits are to a certain extent hyperphalangeal, since several of them possess five phalanges.