No. 521] 



SAUROPOD DINOSAURS 



2<",7 



In the lacertilia the greater trochanter is reduced in 

 size and in some genera is practically obsolete; when 

 present and articulated it looks backward, downward, 

 inward. On the other hand, the second trochanter in the 

 recent lacertilia is enormously developed, looking down- 

 ward, forward, and outward (see Fig. 7). In the sauro- 

 poda, as in the ratite birds, the second trochanter is 

 obsolescent or wholly obsolete. The illustrations already 

 given may help to make my meaning clear. In this con- 

 nection it is well to study the head of the femur and the 

 structure of the pelvis in the struthious birds. The 

 analogy between these and the dinosauria has often 

 been pointed out. The facts to which I have called your 

 attention have great anatomical significance. A com- 

 parison of the head of the femur of the crawling reptiles 

 of to-day with the femur of the sauropoda shows at a 

 glance that in the latter the proximal end of the femur 

 is more like that of birds than of recent lizards. It was, 

 as we all know, in consequence of the recognized simi- 

 larity of the pelvic girdle and the head of the femur to 

 the corresponding structures in the ratite birds that 

 Owen, Marsh and all other competent students have as- 

 signed the femur the position which has almost uniformly 

 been given to it in restorations of the sauropoda, as well 

 as of other dinosaurs. 



But let us for the sake of experiment give the femur 

 the same relative position which it has in the lacertilia, 

 in which the second trochanter plays so great a part. 

 To do this it is necessary to rotate the head of the femur 

 in such a way that the great trochanter will point down- 

 ward and backward. The accompanying diagrammatic 

 illustration shows the femur of the Diplodocus adapted 

 to the acetabulum after the analog of Varanus and 

 Iguana (Fig. 9). Of what earthly use the hind limb of 

 the Diplodocus could have been to him in such a position 

 I leave you to determine for yourselves. It has been 

 suggested that kindly nature, to meet the requirements 

 of the case, must have channeled the surface of the earth 

 and provided the Diplodocus and its allies with troughs 



