Incertae sedis.
PIRATOSAURUS, Leidy.
PIRATOSAURUS PLICATUS, Leidy.
Cretaceous Rept. N. Am., 29, 30, Tab.
Cretaceous of Red River Settlement, Lat. 49 deg., Northern Minnesota. Described from a tooth.
THECODONTIA
Owen in part.
In this suborder we have a singularly generalized group, combining characters of lizards, crocodiles and Sauropterygians. The neural arch of the vertebræ united by suture and the slightly biconcave centrum, resemble the last two, so also the abdominal ribs. The limbs are rather crocodilian, the position of the nares, Plesiosaurian. The clavicle is lacertian, while the three vertebræ of the sacrum and the femur are between these and the Dinosauria.
The most important characters distinguishing these animals from the Sauropterygia are the presence of an elongate sacrum and the more ambulatory form of limbs.
Our knowledge of the order is almost confined to Belodon Meyer, and is derived from that author's descriptions of those large and remarkable reptiles derived from the Keuper of Wurtemburg, the Belodon kapfii Meyer, B. plieningeri Münst., and B. planirostris Meyer.
The American species of the order are known only from the valuable collections made by Wheatley at Pbœnixiille, Pa., and by Emmons at Deep River, in Chatham county, in North Carolina. The former are in my hands for examination and description, and will be the subject of an appendix to this work.
BELODON, Meyer.
Although this genus does not present the swimming extremities of Plesiosaurus and Nothosaurus, its structure in this respect is not much more different from them, than that of the marine turtles is from the terrestial families of the same order. The structure of the sphenoidal region, the peculiar position of the external nostrils, almost above the orbits, with the rhizodont dentition, are points in which they agree. The position of the exterior nares cannot be regarded as an ordinal character, since we see what remarkable differences of position it exhibits in the existing family Varanidæ. There is is every probability that these animals were aquatic. The posterior position of the nostrils, like that in many other marine animals, enabled them to plunge the long muzzle beneath the surface of the water or mud without interfering with respiration.
The dentition of the posterior parts of the mouth has been shown by Von Meyer to be quite different from that of the anterior regions; the latter are prehensile, that is elongate conic, the former cutting, i. e., flattened, broader and with trenchant edges.
