Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/462

Rh 444 R E P T I L E S [CLASSIFICATION. with the remainder of the skeleton secondarily modified for aerial progression. Vertebrae not numerous, procoel- ous; from three to six forming a sacrum; cervical vertebrae exceeding in size the others. No neuro-central suture. Anterior ribs with bifurcate heads. Skull large, bird-like, with long jaws. Os quadratum suturally con- nected with the skull. Orbits very large, with a ring of sclerotic plates. Sternum broad, completely ossified, with a median crest anteriorly. Scapula and coracoid slender, Bird-like; no clavicle. Phalanges of the ulnar digit exceedingly elongate. Pelvis weak; hind limb smaller than fore limb. Bones generally hollow, many with pneumatic foramina. Fam. a. Pterosauria. Jaws toothed ; scapula and coracoid separate. Genera : Ptcrodactylus, lUuimpJwrhynchus, Dimorphodon, from Jurassic formations of Europe ; of small or moderate size. Fam. b. Pteranodontia. Edentulous ; scapula and coracoid solidly united, the former articulating with the common neural spine of the vertebrae. Genus : Ptcranodon, from Cretaceous strata of Kansas ; specimens with a spread of wing of some 20 feet. Order 5. CKOCODILIA. Reptiles with Lizard-like body, and long powerful tail adapted for swimming. Iambs short, especially the anterior; five digits in manus and four in pes ; only three of the digits are clawed. A dermal armour, consisting of flattened bony scutes, covers the back, and in some genera the abdomen. Teeth in a single row, implanted in distinct sockets. Nostrils generally at or near the end of the snout Vertebras with the neuro- central suture persistent. Two sacral vertebras only. The majority of the cervical and trunk ribs double-headed, attached to the diapophysis and centrum of the vertel >]:<. From seven to nine of the anterior dorsal ribs are united with the sternum by sternal ribs. Bones of the skull very solid, firmly united by sutures, as is also the quadrate bone. Heart with a double ventricle. Copulatory orgar single, situated in the cloaca. Fam. a. (or suborder) Proccdia. "With proccelous vertebrae, living genera and the extinct forms down to the Chalk belong this division. Fam. b. (or suborder) Amphiccelia. With amphiccelous vertebr All the genera are pre-Cretaceous : Tcleosaurus, Goniopholis, Stre tospondylus, Stcganotyris, Galcsaurus (?), JBclodon. Order 6. SAUROPTERYGIA (extinct). Marine Reptile with long neck, small head, long tail, natatory limbs, anc a naked skin. Hind and fore limbs identical in structure and form, transformed into Cetacean-like paddles with five digits, which were composed of numerous phalanges and enclosed in a common skin. Teeth in a single row in both jaws, implanted in distinct sockets. Vertebrae amphicoel- ous, with the neuro-central suture persistent; single headed ribs are attached to the long diapophyses of the dorsal vertebrae. Sacral vertebrae two. Quadrate bone suturally united with the skull. A parietal foramen. No sclerotic ring. Neither sternal ribs nor sternum are Fio. 2. Skeleton of Clidastes (after Cope). present; but a system of free abdominal ribs is developed. The pectoral arch consists of a pair of large coracoids, meeting in the median line, and clavicular elements extending from one scapula to the other. Pelvis large, with the ilia, pubes, and ischia not coalesced, and all sharing in the formation of the acetabulum. These characters may not fully apply to all the genera which have been referred to this order, as some are known from, their skulls or other fragments only. The best known are the PI.ESIO.SAUIUANS (q.v.) proper : Ncusti- cosaunis, from the Trias, with paddles in front and ordinary limbs behind ; gigantic forms from the Trias, as Nothosaunis, Simo- saurus, Pistosaurus, or post-Triassic, as Plesiosaurus, and Plio- saurus, Polycotylus, and Elasmosaurus (or Discosaurus) from the Lias and Chalk. 1 Order 7. RHYNCHOCEPHALIA. Lacertiform Reptiles, with four limbs. Vertebrae with flat ends; two in the sacrum ; the tubercular and articular surfaces are united ; ribs single-headed. Os quadratum suturally united with the skull and pterygoid; an osseous infra-temporal bar. Foramen parietale present. Sternum and a system of abdominal ribs well developed. Copulatory organs absent ; urinary bladder present. One recent genus : Hatteria. Represented in the Upper Cretaceous 1 It is very doubtful whether Placodus, originally described as a Fish, belongs to this order.. and Lower Eocene by Champsosaurus, in the Trias by Rhyncho- saurus, Hyperodapedon, and in the Permian by Protcrosaur Sphenosaurus, Telerpcton (?), Saurostcrnum (?). Order 8. LACERTILIA. Lizards. Vertebrae generally procoelous, with short or rudimentary transverse processes; sacral vertebrae not exceeding two; ribs single- headed. Os quadratum articulated with the skull. Parts of the ali- and orbito-sphenoid regions fibro-cartilaginous. Temporal region without, or with only one, osseous bar. Limbs four, two, or absent ; when they are present, a sternum with sternal ribs and a pelvis are developed. Copulatory organs paired ; urinary bladder present. Integuments with horny or sometimes bony scutes. For the numerous recent genera see LIZARDS. Distinguishable representatives of the order appear first in Jurassic formations and thence downward to our period : Acrosaurus, Ardcosaunis, Phuro- saurus, Saphiosaurus, Atoposaurus, and Homceosaurus from the Oolite ; Nuthetcs, Saurillus, Macellodon from the Weald en ; Dolicho- saurus, Adeosaurus, Coniosaurus, Ehaphiosaurus from the Chalk. From Tertiary formations in Europe numerous small remains are known, whilst those described from Australia belonged to much larger forms, showing more or less affinities to the Lizards of the present Australian fauna. A distinct division of this order includes the extinct Mosasaurians, which are, in fact, the Pinnipedes among Lacertilians. Their limbs, of which they had two pairs, are transformed into paddles ; by their long Snake-like