2 
Fishery Bulletin 96( 1 ), 1998 
Symphurine tonguefishes belong to one genus 
( Symphurus Rafinesque, 1810) of approximately 75 
species of small to medium-size, left-sided flatfishes 
(Munroe, 1992). Superficially, these flatfishes are 
recognized in having a small mouth with strongly 
curved and toothed jaws on the blind side, in having 
the caudal, dorsal, and anal fins united, and in hav- 
ing lost pectoral fins, lateral line, and left-side pel- 
vic fin. The right pelvic fin has a reduced number of 
fin rays compared with that for other flatfishes, com- 
prising only four rays, and it is situated along the 
midline of the body. 
Symphurine tonguefishes are the most speciose 
and widely distributed members of the Cynogloss- 
idae, which comprises approximately three genera 
and some 125 species. Within the Cynoglossidae, 
Symphurus forms a monophyletic taxon that is the 
sister group of the Cynoglossus-Paraplagusia lineage 
(Chapleau, 1988). Synapomorphies diagnosing this 
genus (Chapleau, 1988) include a greatly reduced, 
ocular-side, lateral ethmoid lacking an osseous at- 
tachment either to the interorbital complex dorsally 
or to the vomer ventrally, the lateral ethmoid with a 
long posterodorsal arm in contact with the anterior 
process of the supraoccipital, fusion between ocular- 
and blind-side anterior arms of the frontals, replace- 
ment of the anterior portion of the supraoccipital bone 
by a cranial fontanelle (a character perhaps unique 
among flatfishes), all proximal radials anterior to the 
first hemal spine of the caudal region of the body 
equally long and in contact with this spine, lack of a 
lateral line canal on the ocular side (unique among 
flatfishes), and only a single pterygiophore inserted 
in the first interneural space (Munroe, 1992). 
Species of Symphurus have been reported from all 
temperate and tropical oceans (Chabanaud, 1955a, 
1955b, 1956; Mahadeva, 1956; Ginsburg, 1951; 
Menezes and Benvegmi, 1976; Munroe, 1992) but are 
the only cynoglossids found in the New World. In fact, 
it is in these waters where the greatest diversity of 
species of Symphurus is found, with approximately 
30 nominal species recorded from both coasts of the 
Americas (Ginsburg, 1951; Menezes and Benvegnu, 
1976; Munroe, 1992). Compared with other flatfishes, 
Symphurus is the most diverse genus of flatfish oc- 
curring in the New World, and its species occupy the 
greatest variety of habitats within this region. 
In the western Atlantic Ocean, tonguefishes occur 
from the Scotian Shelf (ca. 45°N; Scott and Scott, 
1988) southward to central Argentina (ca. 45°S, 
Evermann and Kendall, 1907; Menezes and Ben- 
vegnu, 1976; Lazzaro, 1973, 1977; Lema et al., 1980; 
this study). Throughout this region, Symphurus spe- 
cies occur in diverse habitats including such shal- 
low-water areas as muddy and silty substrates in 
turbid estuaries, sandy patches in seagrass beds in 
clear tropical waters, and sand substrates on, or ad- 
jacent to, coral reefs. In addition, species of 
Symphurus also inhabit a variety of different sub- 
strates in moderate depths on the continental shelf, 
and some species live even on deepwater substrates 
located on the outer continental shelf and upper con- 
tinental slope. In fact, S. nebulosus and S. margi- 
natus, collected as deep as 810 m and 750 m, respec- 
tively (see below), are among the deepest-dwelling 
flatfishes in the western Atlantic. 
In some demersal fish communities, especially 
those on soft-bottom habitats in the western Atlan- 
tic Ocean (Wenner and Sedberry, 1989), symphurine 
tonguefishes can be abundant and probably account 
for a significant portion of the fish biomass. Although 
not usually targeted commercially, some tongue- 
fishes, other small-size flatfishes ( Etropus , Citha- 
richthys), and juveniles of larger species of flatfishes 
(i.e. Syacium spp., etc.) may represent a significant 
proportion of bycatch in trawl fisheries for shrimps 
and commercially important demersal finfishes 
(Roithmayr, 1965; Anderson, 1968; Furnell, 1982; 
Pellegrin, 1982; Maharaj, 1989; Maharaj and 
Recksiek, 1991). Irrespective of limited commercial 
importance, these relatively small flatfishes, because 
of their abundance and diversity, play significant 
ecological roles as both predator and prey in trophic 
interactions within benthic communities of the west- 
ern Atlantic (Yanez-Arancibia and Sanchez-Gil, 
1986;. 
Accurate identification of fauna in bycatch of com- 
mercial fisheries is important to determine environ- 
mental impacts of commercial fishing on both target 
and nontarget species (Villegas and Dragovich, 1984; 
Sheridan et al., 1984; Rothschild and Brunenmeister, 
1984; Maharaj and Recksiek, 1991; Andrew and 
Pepperell, 1992; Murray et al., 1992; Murawski, 
1994). Such impacts, along with other large-scale 
anthropogenic changes on the biosphere, have high- 
lighted the urgency for careful evaluations of oce- 
anic biodiversity in order to provide baseline infor- 
mation for researchers tasked with monitoring ef- 
fects of such changes on the biotas. Meaningful esti- 
mates of biodiversity, as well as accurate estimates 
of the faunal composition of noncommercial bycatch 
in commercial fisheries, depend upon accurate iden- 
tifications of the taxa involved. 
Accurate identifications, however, require detailed 
systematic studies of the fauna. Uncertainties re- 
garding the taxonomic status of several species of 
western Atlantic tonguefishes, concomitant with in- 
adequate diagnoses, and until recently, the relative 
scarcity of representative size series for many deep- 
sea species, have precluded accurate identifications 
