REPTILES, BIRDS, AND MAMMALS 



449 



The other saurischian stock included the quadrupedal amphibious dinosaurs 

 or sauropods, which were plant-feeders. The line probably began in the late 

 Triassic, but is first known from the Jurassic period, in which it reached its 

 climax; it had nearly died out by late Cretaceous time. It included the largest 



ilium 



pubis 

 acetabulum 



postpubis 



Fig. 28.13. The structure of the pelvis in the two dinosaur stocks. Left, a saurischian; right, 

 an ornithischian. {Redrawn from Romer, The Vertebrate Body, by permission W. B. Saunders 

 Company.) 



Fig. 28.14. Upper Cretaceous dinosaurs in Wyoming, as reconstructed by Charles R. 

 Knight. A pair of Tyrannosaurus rex (right) is about to attack one of the herbivorous 

 horned dinosaurs, Triceratops (left). Tyrannosaurus was the largest of the carnivorous 

 bipedal saurischians, with a length of 47 feet and a standing height of 19 feet. Triceratops 

 grew 20 to 30 feet long and to 8 feet in height, with a skull some 8 feet in length. (Courtesy 

 Chicago Natural History Museum.) 



land animals that have ever lived, whose chief protection against the attacks 

 of the great carnivores seems to have been sheer bulk and weight. Diplodocus 

 was the longest of all dinosaurs, relatively slender in build but stretching almost 

 90 feet from its nose to the end of its whiplike tail. Apatosaurus (formerly known 



