arboricolous, insectivorous, lizard-like reptile from the Lower Permian of Texas. Of Kadaliosaurus, unfortunately, the skull is unknown. Its slender bones were less hollow, and it has also numerous parasternal ribs, unknown in Araeoscelis.
Lower Permian. Araeoscelis Williston, Texas. Kadaliosaurus Credner, Germany.
Family Protorosauridae. Elongate reptiles with long neck and hind legs and hollow bones, from three to five feet in length. Skull imperfectly known, probably with an upper temporal opening only. Sclerotic plates in orbits. Prevomers, palatines, and pterygoid with small teeth. Vertebrae amphicoelous, with persistent intercentra. Seven cervicals, sixteen to eighteen dorsals, two or three sacrals, and a long tail. A single coracoid. Pelvis more or less plate-like, with probably a small pubo-ischiatic vacuity. Ribs single-headed, articulating with centrum, those of the cervical region very slender. Epipodials about as long as propodials, the hind legs much longer than the front. Humeri with ectepicondylar (?) foramen; nine or ten carpals, seven tarsals; phalangeal formula primitive, the digits long. Numerous abdominal ribs.
Fig. 181. Skeleton of Protorosaurus (Protorosauria), modified from Seeley. About one tenth natural size.
Although the first-described fossil reptiles, the protorosaurs are still imperfectly known in the details of their structure, especially of the skull, pectoral, and pelvic girdles. In the elongation of the neck and the slender legs Protorosaurus very much resembles Araeoscelis, and doubtless had similar habits, whether or not the structure of the skull was the same. The numerous known specimens of Protorosaurus differ so much from each other that it is not at all improbable that they represent different genera.
Aphelosaurus is still more problematical, inasmuch as all that is known of it are the trunk and limbs. The limbs resemble those of
