POTTHOFF and KELLEY: OSTEOLOGICAL DEVELOPMENT IN SWORDFISH 



0.25 mm 



1mm 



Figure 26.— Left lateral view of the 15th vertebra from Xiphias gladius, showing the 

 ontogeny. Starting from top left the specimens in millimeters ENL or ESL are as in Figure 

 25. FBr, foraminal bridge; HPo, haemal postzygapophysis; for other abbreviations, see Fig- 

 ure 25. Cartilage, white (except in 5.1 mm ENL specimen in top row left, where entire 

 stippling signifies cartilage); ossifying, stippled. 



0-25mm 



Figure 27.— First and 

 second anteriormost ver- 

 tebrae from a 12.8 mm 

 ESL Xiphias gladius. 

 Top, left lateral view; bot- 

 tom, dorsal view. For 

 abbreviations, see Fig- 

 gures 25 and 26. 



All specimens >6.0 mm ENL had the complete 

 count of eight or nine haemal arches and spines. 



Ossification of the vertebral column started at 

 4.4 mm ENL anteriorly at the bases of the neural 

 arches. All specimens longer than 5.0 mm ENL 

 had some anterior vertebral column ossification. 

 The ossification was in a posterior direction as 

 length increased until all centra including the 

 urostyle were ossifying in some specimens 

 between 6.1 mm ENL and 8.1 mm ESL(Fig.29). 

 In specimens >8.1 mm ESL all entra had some 

 ossification. 



The development of the neural and haemal 

 pre- and postzygapophyses is shown in Figures 

 20-23 and 25-28. Neural prezygapophyses devel- 

 oped on all centra except the anteriormost cen- 

 trum (Figs. 13, 27) and neural postzygapophyses 

 developed on all centra except the urostyle (Figs. 



21-23, 25-28). Haemal prezygapophyses devel- 

 oped on all haemal spines and shifted dorsad and 

 anteriorly onto the centrum during ontogeny 

 (Figs. 20-23, 28); the haemal prezygapophyses on 

 preural centrum 2 and on the parhypural re- 

 mained on the autogenous haemal spine and the 

 autogenous parhypural (Figs. 21-23). 



A neural foramen developed on each centrum 

 except on the urostyle by first developing a 

 neural postzygapophysis (Figs. 25-28). Then an 

 anteriorly directed process developed on the 

 anterodorsal side of the postzygapophysis, which 

 joined the neural spine forming a neural 

 foraminal bridge (Figs. 27, 28). 



The neural prezygapophysis of the second 

 anterior centrum developed an entirely different 

 shape than all other prezygapophyses and could 

 be taken for a neural spine on small juvenile or 



177 



