FISHERY BULLETIN: VOL. 84, NO. 3 



1960). In other scombroids initial ossification was 

 only anterior and posterior (S comber omorus, Sarda 

 ?, Thunnus, Istiophoridae) or only anterior (Scom- 

 brolabrax, Gempylidae, Trichiurus, Xiphias). 

 We believe that the relationship of Acanthocybi- 

 um to the Sardini should be re-examined in the 

 future. 



The Scombrini and Scombrolabrax (Figs. 1, 9) 

 share a primitive development in which the second 

 dorsal fin, anal fin, and pterygiophores develop first 

 from a center anteriorly and posteriorly, and the 

 first dorsal fin and pterygiophores develop second, 

 from a center anteriorly and posteriorly in Scom- 

 brolabrax, but posteriorly only in Scomber except 

 for the first dorsal fin spine, which was added later. 

 The Gempylidae, Thunnini, and Scomberomorus 

 (Figs. 2, 3, 4, 10, 13) share an advanced develop- 

 ment in which the first dorsal fin and pterygiophores 

 develop first from the anteriormost element in a 

 posterior direction, and the second dorsal fin, anal 

 fin, and pterygiophores develop second from a 

 center anteriorly and posteriorly, the first dorsal fin 

 being separate from the second dorsal fin during 

 part of the ontogeny. In Acanthocybium, Sarda, and 

 Thunnini, the development is similar to the advanced 

 development of the Gempylidae and Scomberomorus 

 except in Acanthocybium, Sarda, and Thunnini, the 

 second dorsal fin spine developed first, the first dor- 

 sal fin spine was added later. The first dorsal fin was 

 separate for part of the ontogeny from the second 

 dorsal in Acanthocybium, but we were unable to 

 observe this in Sarda because of the lack of an ade- 

 quate size series. In Trichiurus (Fig. 5), the dorsal 

 fin and pterygiophores develop from the anterior- 

 most element posteriorly. When dorsal fin develop- 

 ment reaches above the anal fin, the anal fin 

 develops from its anteriormost element in a poste- 

 rior direction. Dorsal and anal fin development then 

 proceed posteriorly at about the same pace. Tri- 

 chiurus has a peculiar developmental feature, which 

 was not observed in any other scombroid. It was that 

 the anteriormost dorsal fin spines and anal spine and 

 rays develop before their corresponding pterygio- 

 phores. Pterygiophore development soon overtook 

 fin ray development and during further development 

 more pterygiophores are present than fin rays. In 

 the Istiophoridae and Xiphiidae, dorsal and anal fin 

 development differ from the previously described 

 groups. In the Istiophoridae (Fig. 14) the first dor- 

 sal fin and pterygiophores develop first from a 

 center anteriorly and posteriorly. When the poste- 

 rior portion of the first dorsal fin development 

 reaches above the anterior portion of the anal fin, 

 anal rays and pterygiophores are added mostly pos- 



teriorly, although a few elements develop in an 

 anterior direction. The second dorsal fin develops 

 only in a posterior direction consecutive to the first 

 dorsal fin. In Xiphias (Fig. 15), the second dorsal 

 and anal fins and pterygiophores develop first from 

 a center anteriorly and posteriorly. Development of 

 the first dorsal fin and pterygiophores then is con- 

 tinuous with the second dorsal fin in an anterior 

 direction only. 



The hypurals in all scombroids develop as separate 

 cartilages. Only in Scombrolabrax is there no fusion 

 of the hypurals in the adults. In the Gempylidae the 

 extent of the hypural fusion varies for different 

 genera and we did not observe fusion in the carti- 

 laginous state. For the trichiurids with tails, not 

 enough specimens were available to make observa- 

 tions on hypural fusion. In the remaining scombroids 

 (Scombridae, Istiophoridae, Xiphiidae) hypurals 1-4 

 are fused to one hypural plate in adults. Fusion to 

 one hypural plate came about during ontogeny by 

 fusion of hypurals 1 and 2 to a ventral and hypurals 

 3 and 4 to a dorsal hypural plate, with subsequent 

 fusion of these into one plate. For the ventral plate, 

 cartilaginous fusion occurs in all tribes of the Scom- 

 bridae, but in the Istiophoridae fusion is either from 

 cartilaginous or ossifying hypurals 1 and 2 and in 

 Xiphias it is always from ossifying hypurals (Table 

 1). In Scomber, Acanthocybium, and Istiophoridae, 

 the fusion of hypurals 3 and 4 to the dorsal hypural 

 plate is variable and occurs either during the carti- 

 laginous or ossifying state. In Sarda three speci- 

 mens have fusion of hypurals 3 and 4 in the ossify- 

 ing state. In Scomberomorus and Thunnus the fusion 

 to the dorsal hypural plate occurs always in the car- 

 tilaginous state, whereas in Xiphias it is always in 

 the ossifying state (Table 1). 



The number of centra supporting the caudal rays 

 varies in the scombroids. In Scombrolabrax, Gem- 

 pylidae, Trichiuridae with tails, Scomber, and Istio- 

 phoridae, three vertebrae (including the urostyle) 

 support the caudal rays. In Xiphias only two verte- 

 brae support the rays. In the Scombridae more 

 vertebrae are involved with the support of the 

 caudal rays, except in Scomber. In the Scombero- 

 morus species examined by us, five centra support 

 the rays, but in some species of Scomberomorus only 

 four centra are involved (Collette and Russo 1984). 

 In Acanthocybium (Collette and Russo 1984) and 

 Sarda, five centra are involved with the support of 

 the rays, whereas in Thunnus only four centra sup- 

 port the caudal rays (Table 1). 



Johnson (fn. 3; in press) is of the opinion that 

 Scombrolabrax does not belong in the Scombroidei 

 because it lacks most defining specializations of this 



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