Munroe: Systematics of western Atlantic Symphurus 
3 
for many western Atlantic Symphurus. Inherent dif- 
ficulties with identifications have also prevented 
detailed comparative study of ecologies and life his- 
tories for many tonguefishes occurring in this region. 
Consequently, despite the fact that Symphurus is the 
most speciose western Atlantic flatfish genus, it has 
remained, both systematically and ecologically, one 
of the least known western hemisphere groups of flat- 
fishes, particularly with respect to those species oc- 
curring in bathyal regions. Only in the last three 
decades has intensified study of fish communities 
inhabiting bathyal regions yielded larger samples of 
deepwater tonguefishes. However, this material has 
largely remained unidentified owing to a lack of ad- 
equate descriptions and identification keys for most 
Atlantic Symphurus species. Consequently, ecologi- 
cal information associated with these specimens has 
been minimally assessed. 
Objectives of this study are to revise the species of 
symphurine tonguefishes occurring in the western 
Atlantic Ocean, including evaluation of all nominal 
species described previously; to present detailed de- 
scriptions, diagnoses, and an identification key for 
the 24 species herein considered valid; and to sum- 
marize available distributional and other ecological 
data for each species. Early life history stages of 
Symphurus are abundant in ichthyoplankton collec- 
tions throughout the western Atlantic, but larval 
series of only a few species have thus far been iden- 
tified (Olney and Grant, 1976; Kurtz and Matsuura, 
1994). Meristic data in this paper, coupled with geo- 
graphic information for the species, should facilitate 
identification of larval series for more species. 
This work complements earlier revisionary stud- 
ies on symphurine tonguefishes occurring in the At- 
lantic Ocean (Ginsburg, 1951; Menezes and Ben- 
vegnu, 1976; Munroe, 1990, 1991). Revisionary stud- 
ies are being presented regionally because of the large 
number of species in the genus and need for analysis 
of each species before a phylogenetic study can be 
accomplished. No phylogenetic hypotheses of rela- 
tionships for species of Symphurus have been pro- 
posed, precluding interpretation of geographical or 
ecological information for this taxon within an his- 
torical context. Munroe (1992) recognized nine spe- 
cies groups within Symphurus primarily on the ba- 
sis of shared similarities in interdigitation (ID) pat- 
terns. Although some species groups are perhaps not 
monophyletic, tonguefishes possessing similar ID 
patterns were found to have additional shared fea- 
tures, thus supporting the hypothesis that species 
with the same ID pattern are more closely related 
than those possessing different ID patterns. Species 
descriptions and discussions of distributional and 
size-related life history information for the western 
Atlantic tonguefishes are presented below within the 
context of these species groups. 
Taxonomic history 
At least 34 nominal species of western Atlantic 
symphurine tonguefishes (Table 1) have been de- 
scribed, commencing with the earliest descriptions 
of Pleuronectes plagiusa Linnaeus, 1766 (=S. 
plagiusa, this study), and Pleuronectes plagusia 
Schneider, in Bloch and Schneider, 1801 (=S. 
plagusia). From the early 1800’s until collections 
were made in deepwater habitats during oceano- 
graphic surveys in the 1880’s and early 1900’s, lit- 
erature dealing with western Atlantic Symphurus 
consisted almost entirely of nomenclatural re- 
arrangements of previously described taxa with little 
new information. However, in the mid-1880’s, explo- 
ration of New World deep-sea environments began 
in earnest, and major oceanographic expeditions re- 
covered many new species of fishes. Among these 
were five tonguefishes: Aphoristia ( -Symphurus ) 
nebulosa, A. diomedeana, A. pusilla, A. marginata, 
and A. pigra, described in a series of papers by Goode 
and Bean (1883, 1885b, 1886) and which still repre- 
sent the majority of deep-sea western North Atlan- 
tic tonguefish species. 
In 1889, Jordan and Goss evaluated the validity 
of pleuronectiform species of Europe and the Ameri- 
cas. No new species of tonguefishes were described, 
but these authors proposed that Aphoristia nebulosa 
(=S. nebulosus) differed significantly enough from 
other tonguefishes to be placed in a separate genus 
or subgenus (Acedia ). Also apparent in this and ear- 
lier works (Jordan, 1886a, 1886b) is that subtle varia- 
tions in meristic and morphometric features, char- 
acteristic of members of this taxon, were not fully 
appreciated by these authors. Consequently, charac- 
ters useful in properly diagnosing the species were 
not identified. Jordan and Goss, for example, con- 
cluded that the western Atlantic S. pusillus (Goode 
and Bean) and S. diomedeanus (Goode and Bean) 
were probably not distinct species but represented 
geographically variable populations of the common, 
abundant inshore species S. plagiusa (Linnaeus). 
Likewise, they also considered the eastern Pacific 
species S. elongatus (Gunther) and S. atricaudus (Jor- 
dan and Gilbert) as probably being geographic vari- 
ants of the tropical western Atlantic S. plagusia 
(Schneider, in Bloch and Schneider). These taxa are 
all now regarded as distinct species (Munroe, 1992). 
Later, Jordan and Evermann ( 1898) reviewed pub- 
lished information and evaluated the status of 
tonguefishes occurring in northern and central re- 
