POTTHOFF: DEVELOPMENT AND STRUCTURE OF FINS IN CORYPHAENA 



in a row from the outside of the posterior plate 

 of the cleithrum to the rear of the skull and 

 postcleithra 1 and 2 extended over the abdominal 

 area from the inside of the posterior process of 

 the cleithrum. The supratemporal and two inter- 

 temporals, which belong with the posttemporal to 

 the laterosensory canal (Harrington 1955), orig- 

 inated just anterior to the posttemporal and ended 

 just short of the supraoccipital crest. Except for 

 individual variation there was no specific differ- 

 ence in the shape of bones of the girdle and 

 suspensorium between the two species. The rela- 

 tionship of bones of the pectoral girdle, suspen- 

 sorium, and pelvic basipterygium to each other is 

 showm in Figure 25. 



Formation of the pectoral fin rays started in the 

 dorsal border of the larval pectoral blade (Figure 

 26) and continued ventrad (Figure 27). For equal- 

 sized specimens from 6.5 to 13 mm SL, C. equiselis 



PstCI2 



Pelv 



h 



1.0 mm 



H 



Figure 25. — Lateral external view of left sides of pectoral 

 girdle and suspensorium from a 20.8 mm SL Coryphaena 

 hippurus. Symbols: CI, cleithrum; Cor, coracoid; P, posterior 

 process of the coraco-scapular cartilage; Pelv, pelvic basi- 

 pterygium; PstCl 1, postcleithrum 1; PstCl 2, postcleithrum 2; 

 Ft, posttemporal; R, radial; SCI, supracleithrum; St, supra- 

 temporal (beginning to develop). Stippled, cartilage; dark- 

 ened, bone. 



had more pectoral fin rays than C. hippurus 

 (Figure 28). Of 86 individuals of both species with 

 developing fins <13 mm SL, 5% differed by 2 rays 

 between the left and right sides, 43% differed by 1 

 ray between the sides, and 52% had the same 

 count on both sides. 



The two species differed in length at which 

 development of the pectoral girdle occurred but 

 not in its structure (Table 12). The 6.5 mm NL 

 C. equiselis had the same pectoral girdle de- 

 velopment as a 6.5 mm NL C. hippurus. For 

 individuals of equal length between 7.6 and 18 mm 

 SL, C. equiselis was more advanced. At lengths 

 >18 mm SL specimens of both species had the 

 pectoral girdle equally developed except for the 

 supratemporal-intertemporal bones which were 

 first seen at 13 mm SL in C. equiselis and at 18 mm 

 SL in C. hippurus. 



Regarding development of the pectoral girdle in 

 C. hippurus, the smallest (5 mm NL) specimen 

 had a simple rod-shaped, bony cleithrum, and a 

 coraco-scapular cartilage (Figure 26). The car- 



I- 



0.5 mm 



Figure 26. — Lateral external view of left side of pectoral girdle 

 from a 5.0 mm NL Coryphaena hippurus. Symbols: A, anterior 

 process of the coraco-scapular cartilage; Bl, blade of the larval 

 pectoral fin with two fin rays developing dorsally; CI, cleithrum; 

 D, dorsal process of the coraco-scapular cartilage; P, posterior 

 process of the coraco-scapular cartilage. Stippled, cartilage; 

 darkened, bone. 



301 



