158 Prof. 0. C. Marsh — Families of Sauropodous Dinosaur ia. 



digits in manus and pes ; second row of carpal and tarsal bones 

 unossified ; locomotion quadrupedal. 



(1) Family Atlantosauridee. A pituitary canal; lai'ge fossa for 

 nasal gland. Distal end of scapula not expanded ; coracoid quadri- 

 lateral. Sacrum hollow ; ischia directed downward, with expanded 

 extremities meeting on median line. Anterior caudal vertebrae short, 

 with lateral cavities ; remaining caudals solid ; chevrons single. 



Genera Atlantosaurus, Apatosaurus, Brontosaurus include the 

 largest known land animals. Jurassic, North America. 



(2) Family DiplodoGidee. External nares at apex of skull ; no 

 depression for nasal gland ; two antorbital openings ; large pituitary 

 fossa ; dentition weak, and in front of jaws only ; brain inclined 

 backward ; dentary bone narrow in front. Scapula with shaft 

 somewhat enlarged at summit. Ischia with shaft expanded distally, 

 dii'ected downward and backward, with sides meeting on median 

 line. Sacrum hollow, with three co-ossified vertebree. Anterior 

 caudal vertebrae procoelian, with sides deeply excavated, and chevrons 

 single ; median caudals excavated below, with chevrons double, 

 having both anterior and posterior branches ; distal caudals elongate, 

 with rod-like chevrons. 



Genera Diplodoctis and Barosaurus. Jurassic, North America. 



(3) Family MorosauridEe. External nares anterior ; large fossa 

 for nasal gland ; small pituitary fossa ; dentary bone massive in 

 front ; teeth very large. Shaft of scapula expanded at distal end ; 

 coracoid suboval. Sacral vertebrse four in number, and nearly solid ; 

 ischia slender, with twisted shaft directed backward, and sides 

 meeting on median line. Anterior caudals solid ; chevrons single. 



Genera Morosaurus, Camarasaurus (?) (Amphiccelias). Jurassic, 

 North America and Europe. 



(4) Family Pleurocoelidse. Dentary bone constricted medially ; 

 teeth with crowns like those of Diplodocus. Cervical vertebras 

 elongate, centra hollow, with large lateral openings ; sacral vertebrae 

 solid ; with lateral depressions in centra ; caudal vertebrae solid ; 

 anterior caudals with flat articular faces, and transversely com- 

 pressed neural spines ; median caudal vertebrae with neural arches 

 on front half of centra. Ischia with compressed distal ends, and 

 sides meeting on median line. 



Genera Pleurocoelus, Astrodon (?). Jurassic, North America and 

 Europe. Include the smallest known Sauropoda. 



(5) Family Cardiodontidae. Teeth of moderate size. Upper end 

 of scapula expanded; humerus elongate; fore limbs nearly equalling 

 hind limbs in length. Sacrum solid ; ischia with wide distal ends, 

 and sides meeting on median line. Caudal vertebrae biconcave ; 

 median caudals with double chevrons. 



Genera Cardiodon (Cetiosaurus), Bothriospondylus, Ornithopsis, and 

 Felorosaurus. European, and probably all Jurassic. 



(6) Family Titanosauridae. Fore limbs elongate ; coracoid quadri- 

 lateral. Presacral vertebrae opisthocoelian ; first caudal vertebrae 

 biconvex ; remaining caudals procoelian ; chevrons open above. 



Genera Tttanosatirus and Argijrosaurus. Cretaceous (?), India 

 and Patagonia. 



