THE LIMBS 



167 



the postaxial condyle (Figs. 135, 151). It has more of a sliding or 

 arthrodial joint in land reptiles rotating the foot in extension. It 

 articulates distally — primitively with the calcaneum and astrag- 



FiG. 135. Theromorph limbs: A, Varanops; B, Casea. One half natural size. 



alus. Its lower end in those reptiles, especially cursorial reptiles, in 

 which the astragalus is closely united or fused with the tibia, is obso- 

 lete or lost; in the later pterodactyls (Fig. 155 c) the whole bone has 

 disappeared, as a separate ossification at least. 



