9 



The Bird 



-JL 



PuA 



FIG. 63 Pelvic arch of a Dinosaur 



bone extending backward from the thigh-socket, sepa- 

 rated from the ischium 

 (except at the extreme 

 end) by a long open slit. 

 In other animals these 

 bones are as different in 

 shape as can be imagined, 

 but, almost without excep- 

 tion, the position of each 

 is relatively the same. The 

 extreme extension, forward 

 and back, of the ilium 

 above the back-bone, thus 

 joining with more vertebrae, 

 is directly connected with 

 two-legged erect locomo- 

 tion. A parallel condition 

 is found in some Dinosaurs 

 those extinct giant rep- 

 tiles -- certain of which 

 walked more or less on 

 their hind legs. 



Another fundamental 

 resemblance is found be- 

 tween the thigh-girdles of 

 -Js. Dinosaurs and other rep- 

 tiles and that of a bird in 

 the egg. As is shown in 

 Figs. 63-65, the pubis slants 



slightly forward in both reptile and embryo bird ; but in 



FIG. 64. Pelvic arch of an embryo bird, 

 to show similarity of the two as 

 contrasted with Fig. 65. 



Pur 



FIG. 65. Pelvic arch of an adult bird. 

 (The three figures by courtesy of 

 Prof. H. F. Osborn.) 



