I'OTTHOFF and KELLEY: OSTEOLOGICAL DEVELOPMENT IN SWORUFISH 



Table 7.— Development of dorsal and anal fin pterygiophores in the interneural and interhaemal spaces for 205 Xiphias gladius. 



X - mean. 



'No pterygiophores developed in all or some specimens; these were not used for calculation of means 

 2 No pterygiophores ossified in all or some specimens; these were not used for calculation of means 



Pterygiophores under the middle of the dorsal 

 fin completed development first. Proximal and 

 distal radials first appeared as one piece of carti- 

 lage. Then the distal radial cartilage separated 

 from the proximal radial. Ossification of the 

 proximal radial cartilage started at the middle 

 and spread outwards proximally and distally 

 toward the ends. The ends remained carti- 

 laginous in adults, and small sagittal keels 

 developed ventrad during ossification (Fig. 12). 

 Extensive lateral keels were observed on the 

 pterygiophores in^he largest 668 mm ESL speci- 

 men. 



The posteriormost pterygiophores ossified 

 later, but in the same sequence as those in the 

 middle area. The last pterygiophores supported 

 a double ray in series and a stay was present 

 (Figs. 9, 10). The posteriormost pterygiophore 

 and the stay ossified from the same piece of carti- 

 lage (Figs. 9, 10). 



The anteriormost pterygiophores were the last 

 to ossify. The first anteriormost pterygiophore 

 developed a large anterior sagittal keel (Fig. 



8). 



Distal radials developed from a piece of carti- 

 lage that separated during development from 

 the distal portion of the cartilaginous pterygio- 

 phores and was situated between the bifurcate 

 bases of the serial fin rays (Figs. 8, 12, 13). Ossi- 

 fication of all distal radials occurred after 

 cartilage separation. At first the left and right 

 sides of the distal radial cartilage ossified to form 

 two pieces of bone. Ossification continued until 

 the two bones were joined (Figs. 14, 15). All 

 dorsal fin rays associated with the distal radials 

 had bifurcated bases (Figs. 14, 15). 



1.0mm 



Figure 12.— Left lateral view of a dorsal pterygio- 

 phore from the 11th interneural space of Xiphias 

 gladius, showing the ontogeny. Starting from the 

 top and going to the bottom the specimens' lengths 

 in millimeters ESL are: 15.9, 20.4, 26.7, 33.6, 52.4, 

 225. For abbreviations, see Figure 8. Cartilage, 

 white; ossifying, stippled. 



ANAL FIN 



Anal fin rays first appeared at about the same 

 sizes as the dorsal and caudal rays (Tables 1, 8). 

 The anal rays developed in the anal finfold first 

 at the middle of the fin below myomeres 18-20 in 

 specimens 5.3-6.1 mm ENL. Anal rays were 



169 



