FISHERY BULLETIN: VOL. 84, NO. 3 



elements of preural centra 2 and 3 supported pro- 

 current caudal rays. A procurrent spur and basally 

 foreshortened ray were absent in the Istiophoridae 

 (Johnson 1975) (Table 1). 



FAMILY XIPHIIDAE 



Figure 15 



Ninety-five Xiphias gladius specimens (3.7-19.5 

 ENL or ESL) of this monotypic genus and species 

 studied by Potthoff and Kelley (1982) were reex- 

 amined by us. 



Development of the vertebral column initially 

 started in three places on the notochord: 1) antero- 

 dorsad (neural arches and spines on future centra 

 1-3), 2) posteroventrad on the notochord (hypurals), 

 and 3) ventrad at the center (anterior haemal arches 

 and posterior parapophyses). The neural arches and 

 spines were added in a posterior direction. When 

 the developing neural spines had passed the pre- 

 caudal area, some of the anterior haemal spines 

 started to develop (except the anteriormost two of 



the future caudal vertebrae). Addition of cartilag- 

 inous neural and haemal spines was in a posterior 

 direction, except the first two haemal spines which 

 developed anteriorly. Hypural complex bones were 

 added in an anterior and posterior direction. Ossi- 

 fication of the vertebral column in Xiphias initially 

 started in one place with the anteriormost neural 

 arches and spines. Ossification then proceeded in a 

 posterior direction with the hypural complex ossify- 

 ing last. Saddle-shaped ossifications of the vertebrae 

 as observed in the Scombrolabracidae, Gempylidae, 

 and Scombridae was not observed in Xiphias dur- 

 ing ontogeny. Instead, vertebral ossification was 

 first noted in Xiphias by the appearance of dorso- 

 ventral fractures on the notochord followed by the 

 appearance of ossified vertebrae between the frac- 

 tures (Table 2). 



Cartilaginous dorsal and anal pterygiophores 

 developed simultaneously before the neural and 

 haemal spines had reached the area. The dorsal 

 pterygiophores first developed in a group below the 

 future middle of the dorsal fin above the future inter- 



4 



T 



10 



i r 



12 



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14 



"I r 



16 



20 



22 



24 



26 



i — r 



37 mm ENL 



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4 8mm ENL 



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51 mm ENL 



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 I (I /! II II /I /I {/ r l/ fi^ ff J0.00.0O 00 00 51 mm ENL 



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19 5mm ESL 



Figure 15.— Schematic representation of vertebral column, dorsal and anal fin, pterygiophore, and hypural 

 development in Xiphias gladius, Xiphiidae. Cartilage, white; ossifying, stippled. Scale represents interneural 

 and interhaemal space number and vertebra number. 



674 



