THE HABITAT OF THE SAUROPOD DINOSAURS 465 
Morrison sediments may have been spread out over a vast area. 
In this area of deposition, and living while it was in progress, were 
the Sauropoda and their contemporaries. 
BIOTIC ENVIRONMENT 
I. VERTEBRATES 
The known vertebrate fauna of the Morrison is large and varied. 
The unknown fauna must have also been larger; perhaps, in fact 
quite likely, larger still. Of the mountain fauna of Morrison time 
nothing can be said, but the mountain fauna was not part of the 
sauropod habitat. 
1. Mammalia.—Between twenty and thirty species of mammals 
have been reported from Morrison beds. These were small tricono- 
donts, trituberculates, and multituberculates. They are known 
only from teeth and fragmentary jaws, so that their structure and 
adaptations cannot be made out. It has been suggested that they 
were arboreal. They might serve very well for arboreal members 
of the Morrison fauna. These small mammals could scarcely 
have competed with the Sauropoda for food; they certainly could 
not have constituted food for the Sauropoda in themselves; nor 
could they have been directly formidable as enemies. It has been 
suggested, however, that they may have fed, in part at least, upon 
reptilian eggs. If they did, and if they existed in large numbers, 
they may have been very troublesome companions for the sau- 
ropods. 
2. Aves.—Only one species of bird is known from the Morrison. 
Undoubtedly more were present in Morrison time, but there is no 
direct evidence of their existence. It is not likely that the birds 
had any important effect upon the lives of the sauropods, although 
they may have had something to do with the distribution of species 
of plants which perhaps composed part of the sauropod diet. 
3. Reptilia.—The reptilia of the Morrison were many and 
varied. They all represented degrees of organization and stages 
of evolution which were comparable to the degree of organization 
and stage of evolution of the member of the fauna under discussion— 
the Sauropoda. Undoubtedly there was competition of several 
sorts between the Sauropoda and their reptilian contemporaries. 
