0. C. Marsh — Families of Sauropodous Dinosauria. 487 



Art. LI. — On the Families of Sauropodous Dinosauria ;* 

 by O. C. Marsh. 



The subclass Dinosauria as known to-day, I have divided 

 into three orders : the Theropoda, or carnivorous forms ; the 

 Sauropoda, or herbivorous quadrupedal forms ; and the Pre-. 

 dentata, also herbivorous, and including several suborders; 

 namely, the Stegosaicria and Ceratopsia, both quadrupedal, and 

 the Omithopoda, containing bipedal bird-like reptiles. f 



The principal characters of the order Sauropoda, here 

 discussed, may be briefly stated as follows : 



Order Sauropoda. 



External nares at top of skull ; premaxillary bones with 

 teeth ; crowns of teeth rugose, and more or less spoon-shaped ; 

 large antorbital openings; no pineal foramen; alisphenoid 

 bones; brain case ossified; no columella ; postoccipital bones; 

 no predentary bone ; dentary without coronoid process. Cer- 

 vical ribs coossified with vertebrae ; anterior vertebrae opistho- 

 ccelian, with neural spines bifid ; posterior trunk vertebrae 

 united by diplosphenal articulation ; presacral vertebrae hollow ; 

 each sacral vertebra supports its own sacral rib, or transverse 

 process ; no diapophyses on sacral vertebrae ; neural canal 

 much expanded in sacrum ; first caudal vertebra biconvex ; 

 anterior caudals procoelian. Sternal bones parial ; sternal ribs 

 ossified. Ilium expanded in front of acetabulum ; pubes pro- 

 jecting in front, and united distally by cartilage ; no post- 

 pubis. Limb bones solid ; fore and hind limbs nearly equal ; 

 metacarpals longer than metatarsals ; femur longer than tibia ; 

 astragalus and calcaneum not fitted to end of tibia; feet plan- 

 tigrade, ungulate; five digits in manus and pes ; second row 

 of carpal and tarsal bones unossified ; locomotion quadrupedal. 



(1) Family AUantosaurida3. A pituitary canal ; large fossa 

 for nasal gland. Distal end of scapula not expanded ; coracoid 

 quadrilateral. 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, Xorth America. 



* Abstract of Communication made to Section D, British Association for the 

 Advancement of Science, Bristol Meeting, September 12, 1898. 



f The Dinosaurs of North America, Sixteenth Annual Report, TJ. S. Geological 

 Survey. 84 plates. Washington, 1896. 



Am. Jour. Sci. — Fourth Series, Vol. VI, No. 36. — December, 1898. 

 34 



