262 



Fishery Bulletin 89(2), 1991 



a vertical line anterior to the upper eye, while in S. ocu- 

 lellus the dorsal fin origin usually extends anteriorly 

 only to the vertical through the anterior margin or mid- 

 eye region of the upper eye. Differences in morpho- 

 metries between the two species are that S. oculellus 

 has a narrower body (231-297 SL vs. 278-319 SL in 

 S. plagusia) and attains larger sizes (up to 190 mm SL 

 vs. largest of only 131 mm SL in 5. plagusia). 



Some meristic values of S. plagusia overlap those of 

 11 other species of Atlantic tonguefishes. Symphurus 

 plagusia occurs sympatrically, and occasionally syn- 

 topically, with S. diomedeanus (Goode and Bean) but 

 differs from this species in having 12 caudal fin rays 

 (versus 10 in S. diomedeanus) and in lacking the series 

 of dark spots on posterior rays of the dorsal and anal 

 fins and the pupillary operculum that are present in 

 S. diomedeanus. 



Symphurus plagusia can be distinguished from S. 

 plagiusa (Linnaeus), which has an allopatric distribu- 

 tion in the western North Atlantic, in having 12 versus 

 10 caudal fin rays, and S. plagusia also lacks the well- 

 developed black pigment spot on the ocular-side outer 

 opercle (present in S. plagiusa). In addition, only the 

 ocular-side opercular lining is pigmented in S. plagusia 

 whereas the inner opercular linings on both sides of the 

 body are heavily pigmented in S. plagiusa. Symphurus 

 plagiusa has larger eyes (83-126 HL vs. 64-95 HL in 

 S. plagusia) that are usually equal in position (slightly 

 subequal in S. plagusia). Also, in 5. plagiusa the jaws 

 reach only as far posteriorly as a vertical through the 

 mid-eye region; in contrast, in 5. plagusia the jaws 

 reach a vertical through the rear margin of the pupil 

 or the rear margin of the eye, or the jaws occasionally 

 even extend slightly beyond the vertical through the 

 posterior margin of the lower eye in S. plagusia. In 

 larger ( > 60 mm SL) S. plagiusa, there are 4-8 ctenoid 

 scales on the blind sides of the dorsal and anal fin rays 

 (scales usually absent altogether, or occasionally 1-2 

 scales along bases of fin rays in S. plagusia). 



Symphurus plagusia is not easily confused with other 

 Atlantic species (S. kyaropterygium Menezes and Ben- 

 vegnu, S. trewavasae Chabanaud, 5. normani Chaba- 

 naud, S. piger (Goode and Bean), S. nigrescens Rafi- 

 nesque, S. pusillus (Goode and Bean), S. lubbocki 

 Munroe, and S. reticulatus Munroe) with which it over- 

 laps in meristic features. Symphurus plagusia differs 

 from all of these in its 1-4-3 ID pattern (versus 1-4-2 

 in S. kyaropterygium; 1-3-3 in S. trewavasae and S. nor- 

 mani; 1-3-2 in S. piger, S. nigrescens, S. pusillus, S. 

 reticulatus, and S. lubbocki). In addition, S. plagusia 

 differs from the South Atlantic S. kyaropterygium in 

 caudal-fin-ray number (12 vs. 10) and in lacking the 

 pupillary operculum and dark pigment blotch on the 

 caudal extremity that are present in S. kyaroptery- 

 gium. It differs from the South Atlantic S. trewavasae 



in its caudal-fin-ray count (12 vs. 10) and smaller eye 

 (64-95 HL vs. 114-162 HL in S. trewavasae). Symphu- 

 rus plagusia lacks scales on the blind sides of the dor- 

 sal and anal fin rays and the spotted peritoneum that 

 are present in S. normani. Symphurus plagusia dif- 

 fers from the 1-3-2 species (except S. lubbocki and S. 

 reticulatus) in lacking a black peritoneum. Symphurus 

 plagusia differs from S. lubbocki and S. reticulatus in 

 having no dentition or greatly reduced dentition on 

 ocular-side jaws (versus ocular-side jaws with complete 

 or nearly complete row of teeth in S. lubbocki and S. 

 reticulatus), its much larger size (130 vs. <50mm SL), 

 and pigmentation (dark- or light-brown, usually without 

 crossbands, and with uniformly-pigmented fins, versus 

 light-brown or yellowish body with incomplete cross- 

 bands in S. lubbocki, and dark, chocolate-brown body 

 with X- and Y-shaped markings and vertical fins with 

 alternating series of blotches and unpigmented areas 

 in S. reticulatus). 



Meristic values of 5. plagusia, overlap those of six 

 eastern Pacific species possessing either a 1-4-3 or 1-5-3 

 ID pattern, including S. leei Jordan and Bollman, S. 

 atricaudus (Jordan and Gilbert), S. melanurus Clark, 

 5. williamsi Jordan and Culver, S. fasciolaris Gilbert, 

 and S. melasmatotheca Munroe and Nizinski. Of these 

 species, S. plagusia is most similar to S. melanurus in 

 that both species possess a fleshy ridge on the ocular- 

 side lower jaw, and in both the first dorsal fin ray 

 reaches a vertical equal with or anterior to the anterior 

 margin of the upper eye. The two species are distin- 

 guished in that S. plagusia lacks a pupillary operculum 

 (versus a weakly-developed pupillary operculum usually 

 present in S. melanurus), has fewer scales in a longi- 

 tudinal series (79-89 vs. 89-108 in S. melanurus), has 

 a lightly-pigmented inner lining on the blind-side oper- 

 cle (versus darkly-pigmented inner lining on the blind- 

 side opercle in S. melanurus), and in S. plagusia the 

 posterior dorsal and anal fins and the caudal fin are 

 not darker than the anterior regions (versus progres- 

 sive darkening in posterior dorsal and anal fins and 

 darkly-pigmented caudal fin in S. melanurus). Symphu- 

 rus plagusia differs from the remaining five eastern 

 Pacific species with comparable meristic values in lack- 

 ing a pupillary operculum (present in the others) and 

 in having a fleshy ridge on the ocular-side lower jaw 

 (absent in the others). Symphurus plagusia is further 

 distinguished from S. fasciolaris and S. melasmato- 

 theca in possessing 12 caudal fin rays (versus 10 and 

 1 1 in S. fasciolaris and S. melasmatotheca, respectively) 

 and in lacking an ocellated spot on the caudal fin 

 (present in S. fasciolaris) or pigmented peritoneum 

 (present in S. melasmatotheca). Symphurus plagusia 

 differs further from S. atricaudus and S. williamsi in 

 lacking small ctenoid scales on the blind sides of the 

 dorsal and anal fin rays (present in these other species). 



