order viii DINOSAUKIA 237 



length upward of 20 m. ; 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 Brontosaurus. Upper Jura ; Wyoming and Colorado. 



Sub-Order 3. PREDENTATA. Marsh. (Orthopoda, Cope.) l 



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. 

 Premaxillae edentulous at least in front (rarely with small lateral teeth) ; maxillat 

 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 skull. Vertebral centra solid, opisthocoelous, amphiplatyan, 

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

 Pubes slender and distally free. Post-pubis slender, of variable length, and directed 

 downwards and backwards parallel 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 plantigrade. 

 Dermal armour sometimes strongly developed (Stegosauria), 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 

 Predentata are represented by the bipedal Ornithopodidae ( = Iguanodontia), and 

 the armoured division by the quadrupedal Stegosauridae and Ceratopsidae. 



Family 1. Iguanodontidae.- 



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

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

 aspect, socketed in a single functional row. Cervical and anterior dorsal vertebra, 

 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. Dermal 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- 



1 Literature : 



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



2 Literature : 



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

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

 vols. I.. II.), 1882-84.— Hulk", J. II'., On Hypsilophodon Foxii (Quar. Journ. Geol. Soc. vol. 

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

 p. 1035.— Huxley, T. H., On Hypsilophodon (Quar. Journ. Geol. Soc. vol. XXVL p. 3), 1870.— 

 Leidif, 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, ' >. C, On Hypsilophodon, etc. iJAiner. Journ. Sic. [3], vol. L.), 1895.— N<>i>< >sa, Jr., F. B., 

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



