OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



67 



The same action in the present group would bring 

 A 



In discussing the use of the large foot on the pubis Marsh 1 says: The only probable use is that it 

 served to support the body in sitting down. That some Triassic dinosaurs sat down on their ischia is 

 proved conclusively by the impressions found in the Connecticut River sandstone. In such cases the 

 leg was bent so as to bring the heel to the ground, 

 the foot of the pubes to the ground, nearly or quite 

 under the center of gravity of the animal. The 

 legs and ischia would then naturally aid in keep- 

 ing the body balanced. Possibly this position 

 was assumed habitually by these ferocious biped 

 reptiles while lying in wait for prey. 



When in position (pi. 13) the pubes 

 project forward and downward. Seen 

 from the front they form a Y-shaped 

 figure (pi. 11, fig.l). Their distal ex- 

 tremities are usually found nrmly coos- 

 sified though occasionally immature in- 

 dividuals have them separate. Above 

 this point of contact they were separat- 

 ed by an elongate aperture 120 mm. in 

 length in 4734, U.S.N.M., while above 

 this aperture they meet again forming 

 a strong pubic symphysis. Where the 

 anterior ends of the distal portion pro- 

 ject forward there is a deep notch be- 

 tween the pubes of opposite sides on the 

 median line as shown in figure 1, 

 plate 11. 



Measurements of pubes of Antrodemus valens Leidy. 



No. 4734. 

 TJ.S.N.M. 



Greatest length 



Greatest length of foot 



Greatest width of foot 



Greatest diameter proximal 



end 



Greatest diameter at center 



of combined shafts 



No. 8367, 

 TJ.S.N.M. 



680 

 370 

 185 



210 



165 



740 

 465 

 240 



280 



180 



Ischium (is.). — In the United States fig. 47.— eight pubis of antrodemus valens leidy. no. 



National Museum collections there are 8367, U - S - N - M - Jnat.ske. a, side view, b, distal view 



,-t ■ j> • -, ■ , , _ . OF COALESCED PUBES. a, ACETABULAR BORDER; is, ISCBJAC 



i.nree pairs 01 iscma that pertain to the articulation; v-p, articulation for pubic peduncle of 



species, Antrodemus valens, all in a 2-ood THEILrUM ; *» suture between distal ends of coalesced 



, , j. . ' & PUBES. 



state 01 preservation. Except for dif- 

 ferences in size, all of these bones closely resemble one another in their more 

 important features. 



1 Dinosaurs of North America. 1896, p. 161. 



