metacarpal and phalanx 

 distal carpal 



postminimus 



post-postminimum 



"radial' 



^^^5^^ 



"radial" 



HOLMGREN'S SCHEME FOR NON URODELE HOLMGREN'S SCHEME FOR URODELE 



Figure 6-61. The origin of the tetrapod pectoral limb (cheiropterygium) from the fin of a choanate 

 fish (ichthyopterygium). A, bones of fin of Sounpteros or Eusthenopteron, B, hypothetical intermediate 

 stage toward tetrapod; C, basic tetrapod pattern of elements (except for urodeles) as derived by 

 Holmgren from intermediate stage; D, alternate to C as proposed by Westoll; E, Neocerotodus fin 

 as possible ancestor to the Urodele type pattern, F, as proposed by Holmgren. 



distinct fleshy basal lobe, not as large as that of a sarcop- 

 terygian but intermediate between that group and the 

 actinopterygian. On the basis of its fin, Pnlypterus has been 

 placed in a distinct group called the Brachiopterygii 

 (hrachii — upper part of arm, thus having arms). 



Pelvic appendage The pelvic girdle of the teleost (Figure 

 6-65) consists of a pair of pelvic bones associated with a car- 

 tilaginous core which is T-shaped: the shaft extends forward 

 and represents the pubis, the lateral part of the cross piece 

 represents the iliac process, and the medial one the ischial 

 process. There is a distinct resemblance to the girdle of the 

 choanate, except that the iliac and ischiac processes are not 

 apparent in the definitive bony structure. 



The girdle of Lepisosteus, Amia, or Polyplerus is very similar. 

 Here the cross processes are maximally reduced. In Acipen- 



ser the base of the fin is attached along much of the length 

 of the pelvic cartilage. 



The pelvic fins are generally comparable to the pectoral. 

 Polypterus is peculiar in that the pelvic fin has radials much 

 like the pectoral fin of other fishes, or like the pelvic fin of 

 Acipenser. This suggests that the pectoral fin of Polypterus is 

 specialized. The reliance on the pectoral fins in much of the 

 ordinary swimming of this fish supports this view. 



Chondrlchthyes 



Pecforol appendage The pectoral appendage of the shark 

 (Figure 6-66) is peculiar first for its lack of any dermal ele- 

 ments in the girdle and second for the size and development 

 of the cartilaginous scapulocoracoid which supports the fin. 

 The scapulocoracoid of Squalui has a small separate "supra- 



182 



THE VERTEBRATE BODY SKELETON 



