ECOLOGY, HABITS AND MANNER OF LIFE 



ENVIRONMENT 



One should visualize the known habitat of the horned dinosaurs in North America as a great 

 belt of lowlying lands along the western border of a vast inland sea, which extended from what is 

 now the Gulf of Mexico into northern Alberta and Saskatchewan. When these creatures first appear, 

 in middle late Cretaceous, this sea had already dwindled from its former extent, and by Lance time, 

 according to Schuchert's 1 maps, was merely a narrow vestige confined exclusively to the limits of the 

 United States. To the west of the bordering lands, the great uplift of the Rocky Mountains was 

 already in process of formation; the so-called Laramide revolution, which produced it, also brought 

 about, at the close of the Age of Reptiles, the final drainage of the epeiric sea. The great area 

 wherein the dinosaurs dwelt was for the most part so near the sea level that very slight vertical move- 

 ments would either submerge it beneath the sea or drain it wholly or in part, thus producing at 

 times a rapid change from land to shallow-water or marine conditions over relatively large areas. 

 This would account for the alternation of marine and non-marine strata and the consequent occa- 

 sional breaks in the continuity of the record of ceratopsian history. The actual habitat has been 

 likened to such a region as the Florida Everglades, a vast swamp drained by small interlacing 

 streams the course of which was continually changing. There must have been areas of firmer 

 ground, for not all of the associated dinosaurs were adapted to swamp conditions. The entire region, 

 swamp and drier areas, must have been covered with abundant plant life of an essentially modern 

 aspect, and of sufficient profusion to form, in places, extensive beds of coal. The names of the 

 recorded plants 2 are familiar — ferns, sequoia and other conifers, the gingko, and of deciduous trees, 

 the poplar, beech, elm, sycamore, maple, willow, and oak. In addition to these forest trees there 

 must have been an abundant underbrush and actual swamp vegetation. With the exception of the 

 palms and sequoia, all of these plant genera now thrive in the vicinity of New Haven, and do not 

 necessarily imply a tropical, but perhaps a warm temperate climate with more equable conditions 

 the year round than in present-day Connecticut, for great reptiles could hardly survive a New 

 England winter. The contrast of conditions in the same geographical area then and now is strik- 

 ing, for where vast swamps and deltas and heavily forested lowland formerly prevailed, there is 

 now a great plateau, semi-arid to desert in character. The events which have produced this altera- 

 tion of environment, largely elevation and consequent climatic change, erosion, and deposition, and 

 which have made the area untenable to dinosaurian life, are among the fundamental causes of the 

 passing of a great race. 



There was a curious repetition of conditions at the close of the Jurassic and toward the end of 

 the Cretaceous; for both periods saw the wide extent of what has been called the amphibious-aquatic 

 environment and its peopling by dinosaurian forms. But in the Jurassic, the great amphibious and 

 swamp-dwelling dinosaurs were the saurischian sauropods, such as the gigantic Brontosaurus, while 

 in the Cretaceous, with one apparent exception, 3 these had entirely passed away, at all events in the 

 Northern Hemisphere, and their place was filled by Ornithischia, especially unarmored trachodons 

 and Ceratopsia. Very comparable physical and climatic changes seem to have caused the final 

 extinction of each of these amphibious assemblages. But the question of the origin of these Creta- 

 ceous forms arises, for, as Matthew has shown, neither the trachodons nor the ceratopsians had their 

 initial evolution under such conditions and in such a habitat as that in which we find them, a fact 

 which may account, in part at any rate, for the abrupt appearance, especially of the latter. Matthew 

 says, "These Cretaceous giants .... appear to have evolved, not from amphibious or aquatic dino- 



1 Schuchert, C, and Dunbar, C, 1933, p. 348, PI. 31, maps 2, 3. 



2 Knowlton, F. H., 1930. 

 3 Gilmore, C. W., 1922, A. 



