Munroe: Systematics of western Atlantic Symphurus 
73 
Geographic distribution {Fig. 37 J Western South 
Atlantic inner continental shelf from southeastern 
Brazil to central Argentina. The northernmost record 
for this species (22°53'S) roughly corresponds to the 
region off Cabo Frio, Brazil (Menezes and Benvegnu, 
1976). The specimen (INIDEP 476) from 45°S repre- 
sents the southernmost point of capture for this spe- 
cies. The specimen identified as S. plagiusa by 
Lazzaro (1973) from Puerto Quequen, Argentina (ca. 
38°S), is also this species. 
Bathymetric distribution Symphurus trewavasae 
has been collected over a depth range from 7 (this 
study) to 179 m (Menezes and Benvegnu, 1976), with 
the majority (60/80, 75%) of captures at moderate 
depths (40-80 m) on the continental shelf (Table 10). 
Depth-of-capture information summarized from 
Menezes and Benvegnu (1976) revealed that ca. 85% 
of examined specimens were taken between 50 and 
100 m, and only three at depths shallower than 40 m. 
Menezes and Benvegnu noted that all size classes 
were found at these depths, indicating it is unlikely 
that this species uses shallow inshore habitats as 
nursery grounds. The deepest capture reported for 
the species was for one specimen collected at 179 m 
(Menezes and Benvegnu, 1976). Shallow-water cap- 
tures of S. trewavasae listed in this study include a 
specimen (MNHN 1992-1411) taken at 7 m and three 
others collected between 14-19 m. 
Ecology Nothing else is known of the biology of this 
species. 
Figure 37 
Geographic distribution of Symphurus trewavasae based 
on material examined (discussion of geographic distribu- 
tion appears in species account). 
Remarks Symphurus trewavasae was described by 
Chabanaud (1948a:508) from specimens taken in 
coastal waters off Cabo Frio, Brazil. In his revision 
of western Atlantic Symphurus, Ginsburg ( 1951:185) 
compared briefly the account of S. trewavasae from 
the literature with data for the North Atlantic S. 
plagiusa and suggested that S. trewavasae was pos- 
sibly not distinct from S. plagiusa. He noted that 
purported eye-size differences between the species, 
considered diagnostic by Chabanaud ( 1948a), did not 
always successfully separate them. Furthermore, 
Ginsburg pointed out that although there were modal 
differences in fin-ray counts between the two spe- 
cies, there was sufficient overlap in most features 
examined to necessitate direct comparison of the two 
nominal species, an analysis that he did not perform 
in his study. 
Menezes and Benvegnu (1976:145) studied both 
nominal species in detail and concluded that indeed 
they were distinct. They noted among several dis- 
tinct differences that S. trewavasae had more dor- 
sal- and anal-fin rays, more scales in a longitudinal 
series, a shorter gape, and a larger eye. Furthermore, 
they noted that S. plagiusa characteristically has a 
large, black spot on the upper part of the ocular-side 
opercle that is absent in <S. trewavasae. Results of 
the present study demonstrate that S. trewavasae 
differs from S. plagiusa in lacking scales on blind 
sides of the dorsal- and anal-fin rays and a fleshy 
ridge on the ocular-side dentary (both present in S. 
plagiusa). Symphurus trewavasae has a 1-3-3 pre- 
dominant ID pattern (1-4-3 or 1-4-2 in S. plagiusa). 
Furthermore, the pigmentation pattern of S. 
trewavasae consists of darkly pigmented cross- 
banding, without a spot on the outer surface of the 
ocular-side opercle, and with the isthmus unpig- 
mented, whereas in S. plagiusa the ocular surface is 
usually more uniformly pigmented, or crossbands, 
when present, are rather subdued, usually with a 
well-developed black pigment spot on the outer sur- 
face of the ocular-side opercle, and with the isthmus is 
heavily pigmented. Symphurus trewavasae also has 
higher meristic features than S. plagiusa (dorsal-fin 
rays 88-94 vs. 81-91 in S. plagiusa ; anal-fin rays 73- 
79 vs. 66-75; total vertebrae 47-51, usually 48-49 vs. 
44-49, usually 45—48 in S. plagiusa ; and 67-77 scales 
in longitudinal series vs. 76-86 in S. plagiusa). 
Menezes and Benvegnu ( 1976) also noted that the 
relative sizes of the two species differ ( S . plagiusa 
reaches sizes of 109-174 mm, vs. S. trewavasae , 
which has a maximum reported size of only 139 mm) 
and their ecologies differ. Symphurus trewavasae 
usually occurs on the inner continental shelf at 
depths of 12-190 m, with a center of abundance con- 
centrated mostly between 40 and 110 m (Menezes 
