490 GEOLOGY OF THE DENVER BASIN. 



the orbit, and the lower temporal opening. The first of these lias not been 

 seen in any other Sauropoda; the large antorbital vacuity is characteristic 

 of the Theropoda also; while the other three openings are present in all the 

 known Dinosauria. 



The lower jaws of Diplodocus are more slender than in any of the 

 other Sauropoda. The dentary, especially, lacks the massive character seen 

 in Morosaurus, and is much less robust than the corresponding bone in 

 Brontosaurus. The short dentigerous portion in front is decurved, and its 

 greatest depth is at the symphysis. The articular, angular, and surangular 

 bones are well developed, but the coronary and splenial appear to lie small. 



The dentition of Diplodocus is the weakest seen in any of the known 

 Dinosauria, and strongly suggests the probability that some of the more 

 specialized members of this great group were edentulous. The teetli are 

 entirely confined to the front of the jaws, and those in use were inserted in 

 such shallow sockets that they were readily detached. Specimens in the 

 Yale University Museum show that the entire series of upper or lower teeth 

 could be separated from the bones supporting them without losing their 

 relative position. In iig. 4f> a number of these detached teeth are shown. 



The vertebra] column of Diplodocus, so far as at present known, may 

 be readily distinguished from that of the other Sauropoda by both the 

 centra and chevrons of the caudals. The caudals are deeply excavated 

 below, as shown in fig. 48, while the chevrons have both anterior and 

 posterior branches, as seen in i\<j;. 4<j. 



The type specimen of Diplodocus, to which the skull here figured 

 belongs, indicates an animal intermediate in size between Atlantosaurus 

 and Morosaurus, probably 40 or 50 feet in length when alive. The 

 teeth show that it was herbivorous, and the food was probably succulent 

 vegetation. 



MOROSAURUS. 



Another genus of the Sauropoda, represented by several species of 

 large size, has also been found in the Denver region, and especially in the 

 same horizon farther south. Like Brontosaurus, however, it is much more 

 abundant in the Wyoming Basin, west of the mountains. This genus, 

 described by the writer in 1878, is the type of a distinct family, the 

 Morosauridee. 



