FISHERY BULLETIN: VOL. 78, NO. 2 



5 mm 



FIGURE 24.— Urostyle of a Coryphaena equiselis, 330 mm SL, 

 with disarticulated uroneurals and hypural 5. Dashed lines with 

 arrows point towards place of articulation. Symbols: AStr, 

 anterior strut of urostyle; Hy, hypural; Pr, prezygapophysis; 

 PStr, posterior strut of urostyle; Uns, uroneurals; Ur, urostyle. 

 The articular cartilage is not shown on hypural 5 because of the 

 boiling and drying method of preparation. 



apogonids (Fraser 1972) is probably an oversight 

 by the author since he used cleared and stained 

 material. The lack of articular cartilage in most 

 of the drawings of caudal complexes by Monod 

 (1968) can probably be attributed to the method 

 of skeletal preparation, e.g., boiling and subse- 

 quent drying. 



300 



Autogenous dorsal and ventral hypural plates 

 were observed in adult Coryphaena spp. The 

 fusion of individual hypural bones was considered 

 advanced by Fraser (1972). Even more advanced is 

 the fusion of all hypural bones to one hypural plate 

 and the fusion of this plate to the urostyle as 

 in scombrids (Fierstine and Walters 1968; Pott- 

 hoffl975). 



The formation of articulatory projections of 

 membranous origin during ontogeny at the mid- 

 line of the caudal complex between the dorsal and 

 ventral hypural plates was observed in Cory- 

 phaena spp. (Figures 20-22) as well as in Scom- 

 brolabrax heterolepis (Potthoff et al. 1980), but 

 not in T. atlanticus (Potthoff 1975). 



Both species of Coryphaena had two pairs of 

 uroneurals. The smaller posterior pair gradually 

 moved anteriorly during development and fused 

 to the outsides of the larger anterior pair, until 

 only one pair could be recognized in adults. Fraser 

 (1972) contended that the loss of the posterior 

 pair of uroneurals constituted an evolutionary 

 advance. He did not completely rule out fusion, 

 although he had no evidence for it. There are 

 fishes such as the scombrids which only develop 

 one pair of uroneurals (Potthoff 1975). Loss or 

 fusion of uroneurals can be ascertained through 

 the examination of developmental series. 



Pectoral Fin and Supports 



The following description is based upon juve- 

 niles > 13 mm SL of both Coryphaena species with 

 adult counts of 19-21 rays. These counts were 

 obtained between 19 and 13 mm SL in C. equiselis 

 and between 11 and 13 mm SL in C. hippurus. 

 Individual differences in counts between the left 

 and right pectoral fins were lower in both species 

 of Coryphaena than in four species of Thunnus 

 (Potthoff 1974). Only 1% of 171 Coryphaena spp. 

 examined with adult counts >13 mm SL differed 

 by 2 rays between each side, 18% differed by 1 ray, 

 and 81% had the same count on both sides. The 

 pectoral fin rays were directly and indirectly 

 supported on each side by a number of bones which 

 composed the pectoral girdle and its suspensorium. 

 On each side the pectoral girdle consisted of a 

 scapula (which supported the first fin ray directly), 

 four radials ( which supported the remainder of the 

 rays directly), a coracoid, and a cleithrum. The 

 scapula and coracoid were connected by cartilage. 

 The suspensorium consisted of seven bones. The 

 supracleithrum and posttemporal were attached 



