LEIBY: OPHICHTHIDAE 



107 



progression in larval morphology from some Ophichthus spp. 

 through Quassiremus morphology to sphagebranchin mor- 

 phology which tends to support McCosker's (1977) hypothesis 

 that the other ophichthin lineages arose through modification, 

 reduction, and specialization of the ancestral Ophichthus-like 

 condition. Quassiremus larvae look much like the larvae of 

 some Ophichthus spp., but differ in having the nephros termi- 

 nate over or just anterior to the anus, and in having reduced 

 gill arches. 



The tribe Sphagebranchini is distinguished from the other 

 tribes of the Ophichthinae by a combination of the following 

 adult characters: the pectoral girdle is reduced; the pectoral fin 

 is absent; the gill openings are low to entirely ventral; the neu- 

 rocranium is elongate (neurocranium depth going 4 or more 

 times into its length), generally depressed, and truncate poste- 

 riorly; the gill arches are generally much reduced; the body is 

 equal to or shorter than the tail; the tail tip is sharply pointed; 

 and, the cephalic lateralis system is generally better developed 

 than in other tribes (McCosker, 1977). Larval characters which 

 distinguish this tribe from other tribes in the Ophichthinae or 

 which distinguish lineages within the tribe, are reflections of the 

 adult characters (e.g., reduced gill arches, short gut, dorsal fin 

 origin) (Leiby, 1982). As yet, there are no independent larval 

 characters which confirm the monophyletic origin of this tribe 

 or which confirm the proposed lineages within the tribe, al- 

 though the larval morphology is similar to, and sometimes dif- 

 ficult to distinguish from, the larval morphology of some Oph- 

 ichthini and is consistent with the hypothesis of modification, 

 reduction, and specialization of the ancestral ophichthin con- 

 dition which has been proposed based on adult data. 



The tribe Bascanichthyini, apparently derived from a mod- 

 erately specialized ophichthin-like ancestor (McCosker, 1977), 

 is distinguishable from the other tribes of the Ophichthinae by 

 a combination of the following adult characters: the body is 

 equal to, or longer than the tail; the gill openings are low lateral 

 and crescentic, never entirely ventral; dorsal-fin origin is on the 

 head in most genera; the pectoral fin is reduced or absent; the 

 cephalic lateralis system is reduced; and, the gill arches are 

 generally much reduced (McCosker, 1977). The genus Dalophis 

 is provisionally placed in the Bascanichthyini despite its pos- 

 session of a gill arch skeleton and a body length which are more 

 ophichthin than bascanichthyin, due to its reductions, general 

 cephalic appearance and several osteological characters (Mc- 

 Cosker, 1977). If this placement oi Dalophis is correct, it seems 

 likely that the ancestral bascanichthyin was similar in appear- 

 ance to Dalophis. Larval characters which distinguish this tribe 

 from other tribes in the Ophichthinae are reflections of adult 

 characters (e.g., reduced gill arches, relatively long gut and opis- 

 thonephros, and dorsal-fin origin). Larvae have been identified 

 from each of the three proposed bascanichthyin lineages [e.g., 

 Dalophis (Blache, 1 977; Palomera and Fortuno, 1981), Bascan- 

 ichth\'s(B\?Lc\\e, \971\ Leiby, 1981), Gordiichthys (Leiby. in press), 

 Caralophia (Leiby, in press)], but there are currently no clear 

 larval characters which are useful for elucidating relationships 

 within the Bascanichthyini. With one exception, all of the larvae 

 assigned to the Bascanichthyini are characterized by extremely 

 low to moderately developed gut loops and, except for gut length, 

 nephros length and dorsal-fin origin, look much like larvae of 

 the Sphagebranchini. One larval form which cannot yet be as- 

 signed to a genus, has tentatively been placed in the Bascani- 

 chthyini based on gill arch and caudal osteology although its 



gut morphology is more like some Callechelyini than Bascani- 

 chthyini (Leiby, in press). Discovery of the adults of this species 

 may help clarify relationships within the Bascanichthyini. 



The tribe Callechelyini is apparently derived from a bascan- 

 ichthyin-like ancestor. Adults of this tribe are distinguished by 

 a short neurocranium (neurocranium depth > 33% of its length); 

 the dorsal-fin origin on the head or nape; the body longer than 

 the tail; absence of a pectoral fin; low lateral to entirely ventral 

 anteriorly convergent gill openings; reduced gill arches; reduced 

 cephalic lateralis system; laterally compressed body; small eyes; 

 and, a stout hyoid (McCosker, 1977). Larvae of three of the five 

 known Callechelyin genera have been identified (Leiby, 1984) 

 and are readily distinguishable from larvae of the other ophich- 

 thin tribes. Callechelyin larvae are characterized by moderate 

 to pronounced gut loops; variable but distinctive pigmentation 

 (see Leiby, in press b, for full descriptions); anterior dorsal-fin 

 origin; nephric myomeres more than 56% of total myomeres; a 

 distinct fourth hypobranchial which may be separate from or 

 united with a reduced fifth ceratobranchial (a remnant of the 

 fourth hypobranchial united with a reduced fifth ceratobranchial 

 may occasionally be found in gill arches of larval Sphagebran- 

 chini and Bascanichthyini; a distinct fourth hypobranchial is 

 found in some larval Ophichthini, but, when present, is united 

 with a well developed fifth ceratobranchial); and usually two 

 hypurals rather than the three seen in other ophichthids. 

 McCosker and Rosenblatt (1972) and McCosker (1977) recog- 

 nized the presence of subgeneric lines in the genus Callechelys. 

 Evidence from larval morphology confirms the presence of two 

 subgeneric lineages in Callechelys (Leiby, 1984). Adults of one 

 subgenus have a split urohyal and two rod-shaped elements in 

 the pectoral girdle. The larvae of this subgenus have pronounced 

 gut loops; the fourth hypobranchial free from the fifth cerato- 

 branchial; most or all of the myosepta without pigment; most 

 or all of the anal pterygiophores without pigment; no pigment 

 on the esophagus; pigment on the dorsal surface of each gut 

 loop but no pigment between gut loops; pronounced, round 

 pigment patches in the body wall lateral to each gut loop; and, 

 three to five pronounced, circular postanal pigment patches which 

 consist of subcutaneous and body-wall pigment. Adults of the 

 second subgenus have a simple urohyal and one or two rod- 

 shaped elements in the pectoral girdle. The larvae of this sub- 

 genus have moderate gut loops; the fourth hypobranchial united 

 with the fifth ceratobranchial; dark pigment every third to elev- 

 enth myoseptum, or light pigment on every myoseptum; round 

 or saddle-shaped patches of pigment in the body wall on the 

 ventral margin of the tail extending onto the anal pterygio- 

 phores, or pigment on every anal pterygiophore but none in the 

 ventral body wall; pigment on the esophagus, on the dorsal 

 surface of each gut loop, and between each gut loop; occasionally 

 some body-wall pigment lateral to each gut loop; four to seven 

 irregular, subcutaneous pigment patches on the tail, usually not 

 flanked by body-wall pigment. 



Relationships to other taxa 



The family Ophichthidae is generally considered to be a co- 

 hesive group which is the sole member of the superfamily Oph- 

 ichthoidea. The unique nature of ophichthid larvae supports 

 this allocation. Most workers (e.g., Gosline. 1951; Nelson, 1966b; 

 McCosker, 1 977) consider the Ophichthidae to be a specialized 

 offshoot of the Congridae, although Dean (1972) decried the 



