228 



REPTILIA 



CLASS III 



In the pectoral arch the scapula is longer and stouter than the humerus, 



the coracoid is more or less crescentic or semicircular, and there is no ossified 



sternum. The fore -limbs are small, the carpus is, as a rule, incompletely 



ossified, and the clawed digits are of only moderate size. In the pelvic arch 



the ilium is low and antero-posteriorly extended, the post-acetabular portion 



lower and more elongated than the pre-acetabular, and the acetabulum itself 



is perforate. Both the pubes and ischia meet in ventral symphyses, which are 



often much extended, and apparently served as a support for the body when 



in a crouching or sitting position. The structure of the massive hind limbs 



indicates that progression was mainly bipedal and digitigrade. The proximal 



tarsals tend to form a tibio-tarsus, and in most genera the astragalus bears an 



ascending process, which is immovably applied against the anterior face of the 



tibia, as in young ostriches. Theropoda first appear in the Trias, and become 



extinct in the Cretaceous. 



Family 1. Megalosauridae. Huxley. 



Vertebrae solid and amphiplatyan, except the cerricals, which are opisthocoelous. 

 Pubes long, projecting simply downvjards and forwards, and united in an extended 



ventral symphysis. Extremities pentadactyl, but the inner 

 and outer digits frequently rudimentary. Trias to 

 Upper Cretaceous. 



Zanclodon, Plien. {Plateosaurus, Teratosaurus, 

 Smilodon, v. Meyer ; Gresslyosaurus, Eiitim.). Teeth 

 with serrated anterior and posterior cutting edges. 

 Vertebral column comprising at least sixty vertebrae, 

 three of which are sacral. Limb bones stout. 

 Keuper ; Wiirtemberg. Z. laevis, Plieninger. 



Bimodosauras, Pidancet and Chof. Keuper; 

 Poligny, France. Cladyodon, Owen ; Thecodontosawrus, 

 Palaeosaurus, Riley and Stutch. Trias ; Bristol, 

 England. Bachitrema, Sauvage. Rhaetic ; Autun, 

 France. Epicampodon, Huxley. Trias ; East India. 

 Euscelosaurus, Huxley. Trias ; South Africa. These 

 are imperfectly known genera allied to Zanclodon. 



Anchisaurus, Marsh (Fig. 327). Skull remark- 

 ably bird-like, with very large orbits and antorbital 

 vacuity ; narial opening relatively small ; supra- 

 temporal vacuity subrectangular. Quadrate inclined 

 steeply forwards. Teeth numerous, nearly uniform, 

 and closely set. Fore- limb about two -thirds as 

 large as the hinder pair, with only three clawed 

 digits, the fourth and fifth rudimentary. In the 

 pes the fifth digit is reduced, and the first much 

 shorter than the rest. Total length slightly exceed- 

 ing 1 m. Trias; Connecticut. 



Ammosaurus, Marsh ; Bathygnathus, Leidy ; Arcto- 



saurus, Adams ; Clepsysaurus, Lea. Represented by fragmentary remains from 



the Trias of North America. 



Ceratosdums, Marsh (Figs. 328, 329). Skeleton 4-5 m. Ion- skull 



Fig. 3l'7 



•hisaurus major, Marsh. 



Conn. i/ 4 . 



: Manchester, 



al aspect of right hind foot. 

 Astragalus; c, Calcaneum ; /. 



:;i : t, Tibia; t 2 -t 4 , Distal 

 tarsals; I— V, Digits (after Marsh). 



