FISHERY BULLETIN: VOL. 82, NO. 4 



HYPURAL 5 



HYPURALS 3+4 



HYPURALS 1 + 2 



PARHYPURAL 



a 



PU2 



EPURALS 1 and 2 



URONEURAL 



PARHYPUR APOPHYSIS 



NEURAL SPINES 



FIGURE 39. — Caudal complex in left lat- 

 eral view. a. Scomberomorus semifas- 

 ciatus, New Guinea, 510 mm FL, 3 x . b. 

 Acanthocybium solandri, Revillagigedos 

 Is., 1,068 mm FL, 2x. c. Grammator- 

 cynus bilineatus. New Guinea, 382 mm 

 FL, 4x. 



UROSTYLE 



HYPURAL 

 NOTCH 



HAEMAL SPINES 



cynus and preural centrum 3 is only slightly 

 shortened (Fig. 39c). In Scomberomorus and 

 Acanthocybium, the posterior three neural and 

 three haemal spines bend abruptly away from the 

 vertebral axis and parallel the dorsal and ventral 

 edges of the hypural plate. Only one neural and 

 one haemal spine do so in Grammatorcynus. 



The triangular hypural plate is composed of 

 4-5 fused hypural bones (Potthoff 1975). The 

 dorsalmost (hypural 5) is not fused with the 

 dorsal part of the hypural plate (hypurals 3 and 

 4). The primitive hypural notch is present on the 

 middle of the posterior margin of the hypural 

 plate (Fig. 39). This notch is a remnant of the 

 fusion of the dorsal part of the hypural plate with 



the ventral part (1 and 2). The notch is absent in 

 the more advanced bonitos and tunas (Collette 

 and Chao 1975). In two larger specimens of 

 Grammatorcynus (453 and 521 mm FL), the fifth 

 hypural is partially fused to the dorsal hypural 

 plate instead of being separate as in three small- 

 er specimens (382-410 mm FL, Fig. 39c). One of 

 the diagnostic characters of the Scombridae is 

 that the bases of the caudal rays completely cover 

 the hypural plate instead of only extending part 

 way over the plate as is true of the Gempylidae 

 and Trichiuridae with caudal fins. 



The parhypural is separate from the ventral 

 hypural plate in Scomberomorus and Gramma- 

 torcynus but is fused with it in Acanthocybium 



600 



