Munroe: Systematics of western Atlantic Symphurus 
139 
Figure 61 
Geographic distribution of Symphurus plagusia based on mate- 
rial examined (discussion of geographic distribution appears in 
species account). 
amined were taken. All life history stages occur in 
these shallow areas and only occasionally were indi- 
viduals taken at deeper locations (one specimen at 
51m, three specimens at 40 m, and one specimen at 
37 m). Little is known concerning the biology of S. 
plagusia. Its general rarity in collections indicates 
that it occurs in rarely sampled habitats. 
Remarks Discussion of nomenclature, synonymy, 
and designation of a neotype was provided in Munroe 
(1991). UMML 34347 was incorrectly listed in 
Munroe as having been collected off Panama. The 
correct locality information for this specimen is off 
Guyana at 7°42’N, 57°32'W. 
Comparisons Of western Atlantic tonguefishes, S. 
plagusia most closely resembles S. civitatium. Dif- 
ferences between these species are discussed in the 
“Comparisons” section in the account for S. civita- 
tium. Differences between <S. plagusia and S. oculellus 
were discussed in the “Comparisons” section of the 
account for S. oculellus. 
Symphurus plagusia of all sizes are usually col- 
lected with juveniles and small adults of S. tessel- 
latus. Despite overall similarities in meristic features, 
the two species are quite distinctive. The ocular sur- 
face of S. plagusia is uniformly colored with only faint, 
narrow crossbands in some individuals, it has a well- 
developed fleshy ridge on the ocular-side lower jaw 
(Fig. 3D), and this species lacks a striking black pig- 
ment spot on the outer opercle (some individuals have 
a diffuse blotch on inner opercle where pigmenta- 
tion on inner surface of ocular-side opercle shows 
through), and the inner opercular lining on the blind 
side is relatively unpigmented. In S. tessellatus, in 
contrast, all individuals have a bold pattern of wide 
crossbands, a prominent black spot on the outer sur- 
face of the opercle and a heavily pigmented inner 
opercular lining on the blind side, and this species 
lacks a fleshy ridge on the ocular-side lower jaw (Fig. 
3E). Symph urus plagusia also has a smaller eye (6.4- 
9.5, x =8.2% HL vs. 7.9-11.4, x=9.5% HL in S. 
tessellatus) and lacks small ctenoid scales on poste- 
rior fin rays on the blind side of the dorsal and anal 
fins present in S. tessellatus larger than about 70 
mm. Symphurus plagusia also has modally lower 
meristic values (total vertebrae 49-51 vs. 50-53 in 
S. tessellatus ; dorsal-fin rays 89-97 vs. 91-102, usu- 
ally 93-101; anal-fin rays 73-81 vs. 77-86). 
Symphurus plagusia differs further from S. 
tessellatus in having an almost squarish snout, which 
contrasts with the more pointed snout of S. tessellatus 
(compare Figs. 60 and 62). Also, in S. plagusia, the 
dorsal-fin origin is usually anterior to the vertical 
through the eye whereas in S. tessellatus the dorsal- 
fin originates slightly more posteriorly, usually above 
the anterior margin of the pupil of the upper eye, or 
even as far back posteriorly as the mideye region. 
Viewed from the blind side, the more posterior loca- 
tion of the dorsal-fin origin in S. tessellatus is appar- 
ent in the number of rays occurring along the dorsal 
margin of the body immediately above the space be- 
tween the two nostrils. In S. tessellatus usually only 
the first dorsal-fin ray occurs above the space be- 
tween the nostrils, whereas the second dorsal-fin ray 
lies immediately above the posterior nostril or is 
placed even slightly posterior to the posterior nos- 
tril. In S. plagusia, usually the first two dorsal-fin 
rays occur along the dorsal margin in the space be- 
tween the nostrils, and in many specimens, the first 
dorsal-fin ray is actually situated anterior to the ver- 
tical equal with the anterior nostril. In S. plagusia, 
the jaws usually extend to the posterior margin of the 
lower eye or, in some cases, actually extend slightly 
beyond the posterior margin of the lower eye, whereas 
in S. tessellatus, the jaws usually reach only to the 
middle, rarely to the posterior margin, of the lower eye. 
These two species also differ significantly in over- 
all body size and size at sexual maturation. Sym- 
