724 



GENETICS AND EVOLUTION 



Figure 35.3. Western Canada in the Cretaceous period, about 110,000,000 years 

 ago. '] lie land was low, well watered, and co\ered Avith numerous swamps. Most of the 

 dinosaurs were harmless, plant-eating Ornithischians, reptiles with bird-like pelvic 

 bones. Two types of duck-billed dinosaurs can be seen— three large, uncrested ones 

 in upper portion, and two kinds of crested ones in the lower portion. In the upper 

 right foreground is a heavily armored, four-footed dinosaur covered with bony plates 

 and spines. In the upper right and lower left background are ostrich dinosaurs-tall 

 slender animals, with the general proportions of an ostrich, but with short forelegs 

 and a long, slender tail. (Copyright, Chicago Natural History Museum, from the 

 painting by Charles R. Knight.) 



