greatei 



multangular 

 lesser multangular 

 navicular 

 (radiale 



medial 

 cuneiform 

 .capitate 



navicular- 

 hamate 

 pisiforme ^alus 

 triangular (ulnare) 



lunate (intermedium) 



poir of sesamoids 

 under each joint 

 at this level 



Q 



lateral 

 intermedial 

 medial cuneiform 



pisiforme 

 epiphysis 



A C B 



Figure 6-46. Manus, A and B, and pes, C and D, of man and the opossurr 



cuboid 



calcaneus 



fibula 



and the (ventroanterior) pubis (Figure 6-47). Where these 

 elements come together, there is a deep socket, the acetabu- 

 lum, into which fits the head of the basal limb bone, the 

 femur. The pubis and ischium are partly separated by a large 

 round obturator foramen. The form of the pelvic girdle of the 

 cat and the opossum is very similar except that in the opos- 

 sum the suture lines between the elements are evident. In 

 addition, there is a bone, the marsupial bone, which extends 

 forward from the anterior margin of the pubis. This bone 

 appears to support the body wall and the marsupium, the 

 pouch in which the young are suckled. 



In the monotreme the pelvis is similar to that of the mar- 

 supial. Presence of the marsupial bone in these two groups 

 suggests its presence in their common ancestor, although 

 such a bone is not known in the therapsids. It therefore ap- 

 pears to be a neomorph, and perhaps is an independently ac- 



quired parallelism in the two groups — a slight marsupial 

 fold is observed in the female Echidna. 



The pelvic limb, like the pectoral, has basal stylopodial, 

 middle zeugopodial, and distal autopodial segments. The 

 basal element in the thigh (stylopodium) is the femur, 

 while the tibia and fibula form the middle segment or shank, 

 the zeugopodium. The autopodium is subdivisible into a 

 basal series of tarsals, the basopodium, a series of metatar- 

 sals in the metopodium, and the digits which form the 

 acropodium. The names applied to the various tarsals are 

 indicated in Table 6-3. 



The pelvic limb is remarkably constant in its elements. 

 The foot of the opossum or monotreme is much like that of 

 man, and there is also close agreement in their epiphyses. 

 Again, as in the forelimb, the second to fifth metatarsals, 

 like the tarsals, lack epiphyses. The epiphyses of the distal 



TABLE 6-2 SYNONr/VlY Of NAMES APPLIED TO THE BONES OF 

 THE WR;ST REG/ON, THE CARPAIS, OF TETRAPODS 



ischium 



marsupial bone pubis 



A B 



Figure 6-47. Pelvic girdles of opossum A, and cat, B. 



172 . THE VERTEBRATE BODY SKELETON 



