LIMB GIRDLES 561 



were dragged over the land, and their shoulder girdle was 

 entirely fish-Hke, with a post-temporal connection to the skull 

 (Fig. 437). By contrast the urodeles have lost the whole of the 

 dermal girdle and the Anura retain only the clavicle. In its 

 shoulder girdle, as in other parts of the skeleton, the frog retains 

 much cartilage ; its endoskeletal part has two ossifications, 

 called scapula and coracoid, but, 

 for reasons which will appear be- 

 low, the cartilaginous part should 

 not be called precoracoid. 



Nearly all tetrapods show three 



.-''■"RTem 



Fig. 437. — Shoulder girdle of a stegoce- 

 phalian, Eogyrinus. Right half, inner 

 surface. — From Watson, 1926, Philos. 

 Trans. B. 214, 189. 



Clav., clavicle ; Clei., cleithrum ; P.Tem., post- 

 temporal ; Sc, scapula ; S.Cl., supracleithrum. 



Fig. 438. — A ventral view of the 

 shoulder girdle and sternum 

 of Loemanctits longipes, a 

 lizard. — From Shipley and 

 MacBride. 



I, Interclavicle ; 2, clavicle; 3, scapula; 

 4, coracoid ; 5, precoracoid ; 6, glenoid 

 cavity ; 7, sternum ; 8, sternal bands ; 

 9, sternal portion of a rib. The dotteil 

 regions are cartilage. 



distinct bones in the pelvic girdle, which is entirely endoskeletal 

 and is preformed in cartilage. These are the dorsal ilium, 

 anteroventral pubis, and posteroventral ischium. It would 

 be satisfactory to be able to homologise the pectoral girdle to 

 this plan, but unfortunately modern tetrapods have not 

 more than two cartilage bones in the shoulder. There are, 

 however, some extinct reptiles and some Stegocephalia which 

 have two ventral elements, and it is now generally believed 

 that the primitive tetrapod shoulder girdle consisted of a dorsal 

 scapula, an anteroventral precoracoid, and a posteroventral 



