ORDER viii DINOSAURIA 237 



length upward of 20 ni. ; skull only 0"6 m. long, elevated and laterally com- 

 pressed. In front of the triangular antorbital vacuity is a small maxillary 

 vacuity ; supratemporal fossa very small ; quadrate much inclined forwards. 

 Neck extremely long and flexible, and back extremely short. At least fifteen 

 cervicals, eleven dorsals, four sacrals, and thirty-seven or more caudals present. 

 Sternal bones as in BrontosciAirus. Upper Jura ; Wyoming and Colorado. 



Sub-Order 3. PREDENTATA. Marsh. {Orthojmla, Cope.) ^ 



Large herbivorous Dinosaurs with completely ossified brain case, little or no 

 antorbital vacuity in the skull, and toothless predentary bone in front of the mandible. 

 Fremaxillae edentulous at least in front (rarely with sincdl lateral teeth) ; maxillae 

 and dentary with stout grinding teeth, arranged in one or more functional series. 

 Teeth usually compressed or spatulate, with serrated anterior and posterior cutting 

 edges, but becoming worn down to flattened stumps with age. External nares large, 

 placed at extremity of the shidl. Vertebral centra solid, opisthocoelous, amphiplatyan, 

 or sometimes even amphicoelous. Cerviccd ribs loosely articulated with their centra. 

 Fubes slender and distally free. Fost-pubis slender, of variable length, and directed 

 downwards and backwards parcdlel with the ischium ; the latter with obturator process. 

 Limb bones solid or hollow ; anterior extremities shorter than the hinder pair. 

 Astragalus without ascending process ; hind feet digitigrade or p)lantigrade. 

 Dermcd armour sometimes strongly developed (Stegosaurict), in other cases absent 

 [Iguanodontia). 



This sub-order comprises more or less massive herbivorous Dinosaurs, some 

 of which must have been bipedal in gait, and others quadrupedal. They are 

 distinguished from the preceding groups chiefly by characters of the pelvis, 

 presence of a predentary bone, and edentulous premaxillae. The unarmoured 

 Fredentata are represented by the bipedal Ornithopodidae (^IgnanoiJonfia), and 

 the armoured division by the quadrupedal Sfegosauridae and Ccriifojis/da/'. 



Family 1. Iguanodontidae.^ 



Long axis of skull set at right angles to the neck. Antorbitcd vacuity small, 

 mandibular coronoid process strongly developed. Teeth, when unworn, of petaloid 

 aspect, socketed in a single functional rotu. Cerviccd and anterior dorsal vertebrae 

 opisthocoelous. Pelvis of the quadriradiate type ; post-pubic process long and slender ; 

 fore-limbs only about half as long as the hinder pair ; pes tridactyl, clawed or hoofed ; 

 gait bipedal and digitigrade. Dermcd armour absent. Upper Jura and Cretaceous. 



The pelvis, as has already been pointed out (cf. Fig. 326), is more bird-like 

 than that of any other reptilian group. The ilium generally has its pre- 



■"^ Literature : 



Marsh, 0. C, The Dinosaurs of North America (16th Ann. Kep. U.S. Geol. Surv.), 1896. 



- Literature : 



C'o2je, E. D., On the characters of the skull in the Hadrosauridae (Proc. Acad. Nat. Sci. Philad. 

 p. 98), 1883. — Lollo, L., Notes sur les Dinosauriens de Bernissart (Bull. Mus. d'Hist. Nat. Belg. 

 vols. I., II.), 1882-84. — Halke, J. IF., On Hypsilophodon Foxii (Quar. Jonrn. Geol. Soc. vol. 

 XXIX. p. 522), 1873.— Also ibid. vol. XXX. (1874), p. 18, and Phil. Trans, vol. CLXXIIL (1882), 

 p. IQZo.—Huidey, T. H., On Hypsilophodon (Quar. Journ. Geol. Soc. vol. XXVI. p. 3), 1870.— 

 Leidy, J., Cretaceous Reptiles of the United States (Smithson. Misc. Contrib.), 1864. — Mantell, 

 G. A., Observations on Iguanodon, Hylaeosaurus, etc. (Phil. Trans.), 1825, 1841, 1848, 1849. — 

 Marsh, 0. €., On Hypsilophodon, etc. (Amer. Journ. Sic. [3], vol. L.), 1895. — Nopcsa, Jr., F. B., 

 Dinosaurienreste aus Siebenbiirgeu (Denkschr. Akad. Wissensch. Wien, vol. LXVIIL), 1899. 



