390 Prof. 0. C. Marsh — Classification of Dinosaurs. 



Regarding, then, the Dinosaurs as a sub-class of the Kept ilia, the 

 forms best known at pi'esent may be classified as follows : — 



Sub-class Dinosauria, Owen. 



Premaxillary bones separate ; upper and lower temporal arches ; 

 no teeth on palate ; rami of lower jaw united in front by cartilage 

 only. Neural arches of vertebra? joined to centra by suture; cervical 

 and thoracic ribs double-headed; ribs without uncinate processes; 

 sacral vertebras united; caudal vertebras numerous; chevrons arti- 

 culated intervertebrally. Scapula elongate ; no precoracoid ; clavicles 

 wanting. Ilium prolonged in front of the acetabulum ; acetabulum 

 formed in part by pubis ; ischia meet distally on median line. Fore 

 and hind limbs present, the latter ambulatory and larger than those 

 in front. Head of femur at right angles to condyles ; tibia with 

 procnemial crest ; fibula complete ; first row of tarsals composed of 

 astragalus and calcaneum only, which together form the upper por- 

 tion of ankle joint ; reduction in number of digits begins with the 

 fifth. 



Order Theropoda (Beast foot). Carnivorous. 



Skull with external narial openings lateral ; large antorbital 

 vacuity ; bi'ain case incompletely ossified ; no pineal foramen ; pre- 

 maxillaries with teeth ; no predentary bone ; dentary without 

 coronoid process ; teeth with smooth compressed crowns and 

 crenulated edges. Vertebras more or less cavernous ; posterior trunk 

 vertebrae united by diplosphenal articulation. Each sacral rib sup- 

 ported by two vertebras ; diapophyses distinct from sacral ribs ; 

 sternum unossified. Pubes projecting downward and united distally ; 

 no postpubis. Fore limbs small ; limb bones hollow ; astragalus 

 closely applied to tibia ; feet digitigrade ; digits with prehensile 

 claws ; locomotion mainly bipedal. 



(1) Family Megalosauridce. Lower jaws with teeth in front. 

 Anterior vertebras convexo-concave ; remaining vertebras biconcave ; 

 five sacral vertebras. Abdominal ribs. Ilium expanded in front of 

 acetabulum ; pubes slender. Femur longer than tibia ; astragalus 

 with ascending process ; five digits in manus and four in pes. 



Genus Megalosaurns (Poildlopleuron). Jurassic and Cretaceous. 

 Known forms European. 



(2) Family Dryptosaurida. Lower jaws with teeth in front. 

 Cervical vertebras opisthoccelian ; remaining vertebras biconcave ; 

 sacral vertebras less than five. Ilium expanded in front of ace- 

 tabulum ; distal ends of pubes coossified and much expanded ; an 

 interpubic bone. Femur longer than tibia ; astragalus with 

 ascending process ; fore limbs very small, with compressed pre- 

 hensile claws. 



Genera Dryptosaurns (Lcelaps), Allosaums, Ccelosaurus, Creosaurus. 

 Jurassic and Cretaceous. All from North America. 



(3) Family Labrosanridtx. Lower jaws edentulous in front. 

 Cervical and dorsal vertebias convexo-concave; centra cavernous 



