BUTLER and AHLSTROM: NEW SPECIES, SCOPELENGYS CLARKEI 



(SIO); University of Southern California (USC); 

 Institut fiir Seefischerei, Hamburg (ISH); 

 Museum of Comparative Zoology (MCZ); U.S. Na- 

 tional Museum (USNM); International Indian 

 Ocean Expedition (IIOE); and Field Museum of 

 Natural History (FMNH). 



GENUS SCOPELENGYS ALCOCK 1890 



Type-species Scopelengys tristis Alcock, by 

 monotypy. 



Description. — Head and body laterally com- 

 pressed, eyes small, mouth large. Premaxillary, 

 dentary, and palatines with bands of villiform 

 teeth. Teeth absent at symphysis of upper and 

 lower jaw. Vomer indented at head with teeth in 

 two patches. Teeth on basihyal and on gill rakers. 

 Anterior gill rakers reduced to toothed knobs. 

 Maxillary extending past eye, expanded pos- 

 teriorly. Supramaxillary present. Head and body 

 covered with large deciduous, cycloid scales. Pec- 

 toral fins lateral, extending beyond bases of pel- 

 vic fins. Pelvic fins abdominal. Origin of dorsal 

 fin about over base of pelvic fin. Anal fin com- 

 pletely behind dorsal. Base of adipose fin over 

 posterior half of anal fin. No photophores. No 

 swim bladder in adults. 



D 11-13; A 12-14; P 12-17; V 8; Br 8; C principal 

 19 (1 + 17 + 1); procurrent C 6-9 dorsal and 7-8 

 ventral, hypurals (including parhypural) 4-1-3; 

 epurals 3; uroneurals 2. Urostyle with two centra. 

 As in all myctophiform fishes retaining two ural 

 centra (personal observation reenforced by 

 Rosen and Patterson 1969), the anterior ural cen- 

 trum (labelled PUi -I- Ui in Rosen and Patterson) 

 supports both the parhypural and the 2 inferior 

 hypurals, whereas the posterior ural centrum 

 (U2 in Rosen and Patterson) is associated exclu- 

 sively with the 4 superior hypurals. 



Scopelengys tristis Alcock 



Scopelengys tristis Alcock 1890:302. 



Scopelengys dispar Garman 1899:254, plate 54, 

 fig. 2-2d. 



Scopelengys lugubris Garman 1899:400, (syn- 

 onym Scopelengys dispar). 



Scopelengys whoi Mead 1963:255, fig. 1. 



Description of Adult 



Body moderately slender, maximum body depth 



at nape, tapering to a narrow caudal peduncle 

 (Figures lA, 2A); body depth at dorsal origin 

 11.7-19.8 (15.4); least depth at caudal peduncle 

 5.6-8.3 (6.8). Dorsal profile of head slightly con- 

 cave; head length 24.4-33.9 (29.4); head depth 

 16.7-25.5 (20.2); eye small, orbit 3.1-4.2 (3.5); 

 snout 7.5-10.1 (8.8). Width of maxillary as per- 

 centage of its length 29.9-36.7 (32.2). Snout to: 

 dorsal fin origin 36.1-47.0 (41.9); anal fin origin 

 56.4-72.6 (66.4); ventral fin origin 34.7-48.0 (41.8). 

 Meristic Data.— D.11-13 (11.5); A 12-14 (13.0); 

 P 14-17 (15.4); vertebrae 29-32 (30.8); total gill 

 rakers 7-11 (8.5). 



Larvae 



Twenty-five specimens 3.5-10.3 mm were avail- 

 able from the eastern Pacific. Measurements and 

 counts were given for two eastern Pacific (EAS- 

 TROPAC) specimens (6.2 and 6.4 mm SL) by 

 Okiyama (1974) and the smaller specimen illus- 

 trated. The larvae have a small round eye with- 

 out choroid tissue, a snout as long proportionately 

 as in adults, a gut terminating just forward of the 

 anal fin, and a gas bladder, best seen on late 

 preflection and flexion specimens, becoming 

 obscured by overlying musculature in larger 

 postflexion specimens. 



Rays form early in the pectoral fins; a 3.5-mm 

 specimen has large pectorals extending posteriad 

 to the anus; caudal fin forms and notochord flex- 

 ion occurs between ca. 5 and 7 mm; dorsal and 

 anal fins form during flexion; pelvic buds appear 

 between 6.5 and 7.0 mm; fin formation, including 

 procurrent caudal rays, complete by about 10.0 

 mm. Pigmentation is scanty; pigment develops on 

 dorsal margin of peritoneal cavity, spreading lat- 

 erally on prefiexion and flexion stage specimens 

 but becoming obscured on postflexion larvae; 

 preflexion larvae have a series of 6 or 7 small, 

 inconspicuous spots along the ventral margin of 

 the tail which are later obscured by the anal fin 

 formation and lacking on late postflexion larvae; 

 head pigment, best developed on postflexion 

 specimens, consists of a striking horizontal bar 

 extending from snout to eye and continuing be- 

 hind the eye onto the operculum (Figure 3A). 



Distribution 



Records are from the tropical Atlantic, Pacific, 

 and Indian oceans (Figure 4). The range is ex- 

 panded poleward in the eastern part of the Pacific 



143 



