THE HABITAT OF THE SAUROPOD DINOSAURS 469 
conditions point more to an abundance of rainfall than to a wide- 
spread lack of it. We may therefore conclude, provisionally at 
least, that the climate was warm and moist. 
INTERPRETATION OF HABITAT 
From the evidence of the physical characters of the Morrison 
formation and from the nature of its flora and fauna it may be 
possible to work out, to a certain degree at least, the environment 
which surrounded our American Sauropoda. In the first place, 
there was a vast plain in the Western United States, possibly 
extending northward into Canada; this plain was low throughout 
its entire extent, but slightly higher in the west than in the east; 
it was bordered on the west by mountainous country. From this 
mountainous area streams issued, bringing sediment and depositing 
it along the western border of the plain. The streams, upon leaving 
the mountains, became sluggish and split up into a large number of 
distributaries. As in the great plains of China, streams would be 
split up into distributaries and united again. Between the streams, 
and more or less connected with them, were lakes. A considerable 
amount of vegetation was present, especially along the stream and 
lake banks. In this respect the plain would resemble the interior 
of Florida, which has often been suggested as the type of habitat 
possible for sauropod dinosaurs. Our Morrison plain would differ 
from Florida, however, in its extent, the central Florida swamps 
being relatively small and the Morrison plain being a million square 
miles or more in area. In some of the interstream areas, especially 
in the west, vegetation may have been more scarce. Active 
volcanoes were present somewhere, either in the mountains or on 
the plain. Somewhere to the southeast was the sea, but its exact 
border is not known, especially with regard to the earlier part of 
Morrison time. On this plain lived an extensive terrestrial, 
amphibious, fluviatile, or lacustrine fauna. Little, primitive 
mammals climbed the trees or scurried over the ground; here and 
there some birds flew through the air; along the shores of the lakes 
and rivers lived some Sphenodon-like rhynchocephalians; ptero- 
saurs flew through the air; some turtles swam about in the water; 
crocodiles inhabited the stream and lake banks, and infested the 
