POTTHOFF: DEVELOPMENT AND STRUCTURE OF FINS IN CORYPHAENA 



Figure 32. — Lateral internal view of left basipterygium from a 449 mm SL, ^orypnaena 

 hippurus. For explanation of symbols, see Figure 31. Stippled, cartilage; darkened, bone. 



Figure 33. — Posterior view of left basipterygium after left 

 pelvic fin had been removed from a 449 mm SL Coryphaena 

 hippurus. For explanation of symbols, see Figure 31. 



species a fin bud developed first on the abdomen 

 (Table 13). Simultaneously to the fin bud appear- 

 ance, two cartilaginous basipterygia developed 

 internally at 7 mm SL in flexion larvae of C 

 hippurus. In C. equiselis it probably occurred in 

 flexion larvae betw^een 6 and 7 mm SL, but the 

 smallest available specimen measured 7 mm SL 

 (Table 12). The pelvic fin rays developed in the 

 fin bud after basipterygium formation. Fin ray 

 appearance was from the outside of the specimen 

 towards its midline in both species, so that the 

 first ray to appear was the spinous ray. In C. 

 hippurus the pelvic fin ray development began at 

 7-7.5 mm SL and was completed at 10.7 mm SL, 

 and in C. equiselis it began at 7.3 mm SL and was 

 completed at 8.6 mm SL. 



Each cartilaginous basipterygium in both spe- 

 cies was cylindrical with its base expanded poste- 

 riorly near the fin bud (Figure 34). The cartilag- 

 inous projection of the posterior xiphoid process 

 developed posteriorly at the inner corner of the 

 expanded base (Figure 34). Ossification of the 

 basipterygium cartilage to the central part began 

 in both species at the center and progressed 

 anteriorly and posteriorly as the larvae grew 

 (Figure 34). For C. hippurus it began at 8.7-10.8 

 mm SL, and for C. equiselis at 8.7 mm SL (Tables 

 12, 13). After the cartilaginous central part of the 

 basipterygium had ossified, all structures of mem- 

 branous origin developed simultaneously; these 

 were the anterior xiphoid process and the four 

 wings (Figure 34). All wings developed from 

 the base in an anterior direction. The posterior 

 xiphoid process was of cartilage origin and started 



307 



