POTTHOFF ET AL.: DEVELOPMENT OF SCOMBROID FISHES 



Figure 6.— Left lateral view of the anteriormost three dorsal pterygiophores inserting in the interneural 

 spaces 2-4 from a juvenile Trichiurus lepturus 510 mm TL. D, distal radial; Ns, neural spine; P, proximal 

 radial; R, ray or spine; X, a new pterygiophore element of unknown homology. Cartilage, white; bone, 

 stippled. 



arches and proceeded in a posterior direction. 

 Saddle-shaped ossifications of the vertebrae as seen 

 in Scombrolabrocidae, Gempylidae, and Scombridae 

 were not observed in Trichiurus, instead vertebral 

 ossification started laterally on both sides of the 

 notochord as a thin strip of bone. During further 

 development the lateral strip elongated dorsad 

 and ventrad joining the strip from the opposite 

 side and forming a ring of bone around the noto- 

 chord. 



Trichiurus first developed two of the three ante- 

 rior dorsal fin spines. Next the first dorsal pteryg- 

 iophore developed. Then dorsal pterygiophores, the 

 third dorsal fin spine, and the dorsal fin rays were 

 added in a posterior direction, with the pterygio- 

 phore development being slightly posterior to the 

 ray development and considerably posterior to the 

 neural arch and spine development. The single large 

 anal spine developed first after dorsal fin ray and 

 pterygiophore development had dorsally passed the 

 anterior portion of the anal fin fold. Next, the large 

 first anal fin pterygiophore and some haemal arches 

 and spines developed. Further development con- 

 sisted of the addition of anal fin rays, pterygio- 



phores, and haemal arches and spines in a posterior 

 direction. The haemal arches and spines and the anal 

 fin rays developed slightly anterior to the anal pte- 

 rygiophores. The anal pterygiophores were slightly 

 anterior to the dorsal fin ray and pterygiophore 

 development (Table 2). 



Trichiurus lacked predorsal bones. The first dor- 

 sal pterygiophore supported two fin spines (one 

 supernumerary) and originated from one piece of 

 cartilage. In larvae the first dorsal pterygiophore 

 inserted between the split neural arch and spine of 

 the first centrum, thus inserting into the first and 

 second interneural spaces. However, in adults the 

 first dorsal pterygiophore inserted into the second 

 interneural space. All following interneural and 

 interhaemal spaces accommodated one pterygio- 

 phore per space. The first anal pterygiophore was 

 larger than the following pterygiophores, but it 

 developed from one piece of cartilage and sup- 

 ported one supernumerary spine and one ray (Table 



1). 



The pterygiophores in Trichiurus and probably 

 in most if not all species of the Trichiuridae are 

 anatomically different from those of other scom- 



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