GORDON ET AL.; OPHIDIIFORMES 



317 



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Fig. 163. Larva of Pyramodon ventralis. (top) uncat., 21°20-30'N, 158°20-30W, 19 Dec. 1977. Larva oi Snydehdia bothrops. (bottom) MCZ 

 uncat., RHB 1263, Chain 60, 12°58'N, 73°34W, 29 May 1966, 0-120 m, IKMT. 



terial of Echiodon dentatus (Padoa, 1956j) and E. dawsoni (Ol- 

 ney and Markle, 1979) but are not normally retained in pre- 

 served material. Meianophores are variously present at the 

 symphysis of the lower jaw, on the snout, head, vexillum, swim- 

 bladder, trunk, and tail. Preliminary studies (Padoa, 1 956j; Rob- 

 ertson, 1975b; OIney and Markle, 1979; Markle and Olney, 

 1980) indicate that pigmentation may be regionally useful as an 

 aid to identification but seems problematic as an indicator of 

 higher relationships. 



Osteology.— The placement of the pelvic fins, which defines the 

 subfamily Ophidiinae, shows marked ontogenetic change (Gor- 

 don, 1982). In early larvae, the cleithra lack the forward exten- 

 sion and the pelvic fins (appearing by about 7 mm NL) are 

 supported in a jugular position. By 20 mm SL, the bony exten- 

 sion of the cleithra develops and begins to elongate anteriorly. 

 The pelvic fins, which are supported at the symphysis, migrate 

 forward and are present in the characteristic mental position in 

 the juveniles. The presence of pelvic fins in the jugular position 

 has occasionally caused the confusion of early larvae with other 

 ophidioids. 



The general structure of the vexillar ray is described by Olney 

 and Markle (1979) and Govoni et al. ( 1 984). External variations 

 of vexilla are in length, ornamentation, pigmentation, and po- 

 sition. Some variation such as length and ornamentation ap- 



pears to be an artifact (Govoni et al., 1984). In several species, 

 the vexillar pigmentation and ornamentation are curiously re- 

 peated in the caudal filament (Fig. 162). Variation in the sup- 

 porting proximal radial is seen in its shape, its position relative 

 to the first adult dorsal fin ray and to vertebrae, and in fusion 

 with the proximal radial of the first dorsal fin ray. In addition, 

 the supporting proximal radial may or may not be retained in 

 adults (Fig. 161C, D). Its retention provides a means of iden- 

 tifying the location of the vexillum and can aid in larval iden- 

 tification. Its absorption, however, appears to have occurred 

 independently in several genera. In the pyramodontines (Markle 

 and Olney, 1980) and Carapus (Olney and Markle, 1979) there 

 is also an accessory cartilage in front of the second neural spine. 

 Its origin and function are unknown. Carapus (and presumably 

 Encheliophis) and the pyramodontines also have the most for- 

 wardly placed vexilla, usually above or in front of the first anal 

 fin ray. Carapus (and presumably Encheliophis) differs from the 

 pyramodontines and all other carapids in displacement of the 

 first adult dorsal fin ray far posteriad of the vexillum (Fig. 162). 

 Modified ribs on the anterior vertebral centra of carapids and 

 ophidiines are associated with sound production/reception (Rose, 

 1961; Courtenay and McKittrick, 1970; Courtenay, 1971) and 

 develop in early stages in carapids (Olney and Markle, 1979). 

 In Carapidae, the first two ribs are movable and all subsequent 

 ribs are rigid (Markle et al., 1983). A simple recurved third rib 



