JOHNSON: PERCOIDEI 



497 





Fig. 264. Scjiiaiiig clcctromicrographs of epillicliuiu ol laival Uolpliin and amberjack at various magnifications. (A) Coryphaena hippurus, 

 17.0 mm SL, 55x;(B) C. hippurus. 17.0 mm SL, 400x;(C) Seriola sp., 11.2 mm SL, 55x;and(D) 5. sp., 11.2 mm SL, 2,000 x. 



It has a well developed bony stay, a single, partly ossified pre- 

 nasal canal unit and an unmodified coracoid. 



Within the carangoids, the Coryphaenidae, Rachycentridae 

 and Echeneididae form a monophyletic group, here referred to 

 as the echeneoids. Adult echeneoids are specialized with respect 

 to the Carangidae in the following features: absence of predorsal 

 bones; anterior shift of the first dorsal pterygiophore forward of 

 the third intemeural space; presence of several anal pterygio- 

 phores anterior to the first haemal spine (vs. one in carangids 

 and most other percoids); loss of the so-called beryciform fo- 

 ramen in the anterior ceratohyal; and tubular ossifications sur- 

 rounding both prenasal canal units. Larval echeneoids are also 

 specialized with respect to carangids (larvae of Ncmatistius are 

 unknown). Whereas larval carangids are moderate to deep-bod- 

 ied, hatch at small sizes (1-3.5 mm) and complete dorsal fin 

 and anal fin rays in conjunction with or soon after flexion, 

 echeneoid larvae (Fig. 261 A-C) are very elongate, hatch at large 

 sizes and complete dorsal fin rays at two to three times the size 

 at flexion (sec Table 121). Larval morphology thereby corrob- 

 orates the hypothesized monophyly of the echeneoids. 



Although a sister-group relationship between the Coryphaen- 

 idae and either the Rachycentridae or the Echeneididae has not 

 been previously proposed, it has often been suggested that 

 Rachycentron and the echeneidids are sister groups. This hy- 

 pothesis was based on general external similarity including the 

 remarkable resemblance in body form, color pattern and caudal 

 fin shape between juveniles of Rachycentron and Echeneis nau- 

 aa?«(B6hlke and Chaplin, 1968). Because the juvenile features 

 of Rachycentron are shared by only one species of echeneidid, 

 they do not provide evidence for a sister-group relationship 

 between the Rachycentridae and the Echeneididae, nor does a 

 detailed osteological comparison of the two groups. The eche- 

 neidids are highly modified in almost every aspect of their os- 

 teology compared to both Rachycentron and Coryphaena, and 

 with two exceptions (absence of a median cranial crest and 

 fusion of the prenasal ossifications), the only specializations 

 shared by both Rachycentron and the echeneidids are also shared 

 by Coryphaena. The following are autapomorphies of the Eche- 

 neididae: spinous dorsal fin modified as an attachment disc 

 covenng the dorsal surface of the cranium; first neural arch fused 



