286 



VERTEBRATE SKELETON 



is divided into two condyles, with an entepicondylar groove or 

 foramen above. Radius and ulna are nearly equal, the olecranon 

 moderate or obsolete. The carpus (fig. 305) has been greatly 

 modified in recent species where it has two proximal and two distal 

 bones. The proximal (the intermedium probably fused with one of 

 them) are the larger, while in the distal row the bone on the radial 

 side is the fused carpale i and the two centralia ; the second carpale 

 has united with the second metacarpal, while carpalia 3 to 5 have 

 united as the ulnar element, near which is a large pisiforme. The 

 phalanges are 2, 3, 4, 4, 3. 



The round head of the femur scarcely projects from the shaft, 

 the weak fibular trochanter is a long ridge, the tibial trochanter is 

 reduced and the distal end of the femur has two articular surfaces. 



The tibia, larger than the femur, 

 occupies most of the articular surface 

 of the femur, and distally it articu- 

 lates with the tritibiale, the fibula 

 touching both this and the fibulare. 

 Tritibiale and fibulare are larger than 

 the other tarsal bones, one of w^hich is 

 formed of tarsaha i to 3, the other 

 of 4 and 5. The intra tarsal hinge is 

 like that of Chelonia. The fifth digit 

 is rudimentary, and consists of a 

 short metatarsal attached to the 

 fibular tarsale. 



Fig. 309. — A. hind foot of Antro- 

 demus valens (Gilmore, '20); B, fore 

 foot of Allosaurus fragilis (Gilmore, 

 '15). a, talus; c, calcaneum; /, fibula; 

 h, humerus; j, intratarsal joint; m, 

 metatarsals; r, radius; re, radiale; t, 

 tibia; u, ulna; 1-3, digits (Gilmore's 

 numbering) . 



DiNOSAURiA. — The limbs of Dinosaurs 

 are less known than most of the axial 

 skeleton, least known in the distal parts. 

 Sauropods and some Ornithischia had 

 solid bones, others had them hollow and possibly pneumatic. Fore and 

 hind limbs are nearly equal in Sauropods; in Theropods and many Ornithischia 

 the fore limbs are much smaller than the hind, indicating a bipedal locomotion. 

 The Sauropods are plantigrade, with hoofed digits, the other sub-orders digiti- 

 grade (fig. 292), some having prehensile claws. The basipodal parts were 

 incompletely ossified, the distal row being rarely represented in the fossils. 



The humerus usually has a strong crest for the radial tuberosity. Both 

 radius and ulna are well developed, the latter with a strong olecranon. The 

 functional digits vary from five to three, the others showing various degrees of 

 reduction. The strong femur (enormous in some species) has a middle trochan- 

 ter except in the armored Stegosaurs. Tibia and fibula are complete and the 



