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Fishery Bulletin 96(1 ), 1998 
discussed in the “Comparisons” section of accounts 
for these other species. 
Symphurus tessellatus is distinct from other spe- 
cies including S. ginsburgi, S. billykrietei, S. 
stigmosus, S. marginatus, S. diomedeanus which is 
sometimes collected with S. tessellatus, and S. 
jenynsi, a species that sometimes co-occurs with S. 
tessellatus in the southern extent of its range. Dif- 
ferences between <S. tessellatus and these others are 
discussed in the “Comparisons” sections of the ac- 
counts for these species, respectively. 
There are nine eastern Pacific Symphurus with some- 
what similar ID patterns, comparable fin-ray counts, 
or pigment patterns reminiscent of those observed in 
S. tessellatus. Of these nine, only S. chabanaudi and 
S. elongatus are similar to S. tessellatus in that they 
lack a pupillary operculum. Of all species in the genus, 
S. tessellatus is most similar in form, size, and pigmen- 
tation pattern to S. chabanaudi. However, S. tessellatus 
is distinguished from S. chabanaudi primarily by dif- 
ferences in number of dorsal- (91-102 vs. 98-109 in S. 
chabanaudi) and anal-fin rays (74-86 vs. 82-92); total 
vertebrae (48-54, usually 50-53 vs. 52-57, usually 53- 
56); and longitudinal scales (81-96 vs. 92-102 in S. 
chabanaudi). The two species also differ in relative fre- 
quencies of occurrence of particular ID patterns. In S. 
chabanaudi, 50% (49/95) of the individuals had a 1-5-3 
ID pattern, whereas only 30% (28 specimens) featured 
a 1-4-3 pattern. In contrast, 209 of 278 (75%) S. 
tessellatus possessed a 1-4-3 ID pattern, whereas only 
5% (15 specimens) had a 1-5-3 pattern. 
There is some overlap in fin-ray and vertebral 
counts between S. tessellatus and S. elongatus', how- 
ever, these counts are the only similarities between 
these otherwise distinctive species. Symphurus 
tessellatus has a pattern of crossbands on the body 
and a large, black blotch on the ocular-side opercle, 
whereas in S. elongatus, the body is uniformly pig- 
mented without crossbands and this species lacks 
the prominent black blotch on the ocular-side opercle. 
Further differences include the small ctenoid scales on 
blind-side dorsal- and anal-fin rays in S. tessellatus 
(lacking in S. elongatus) and absence of a fleshy ridge 
on the ocular-side lower jaw in S. tessellatus (a well- 
developed ridge present in S. elongatus). Symphurus 
tessellatus also has a much larger eye (15-21 SL) com- 
pared with that of S. elongatus (9-15 SL). 
Discussion 
Biogeography 
Symphurus , the only cynoglossid genus in the west- 
ern Atlantic Ocean, is the most widespread tongue- 
fish genus with members occurring worldwide in all 
temperate and tropical oceans. No fossils of 
cynoglossid fishes are known (Menon, 1977), and 
relative age of these flatfishes is unknown. The dis- 
tribution of Symphurus throughout the Pacific and 
Atlantic oceans suggests that the genus evolved prior 
to the Miocene Epoch when interconnections existed 
between Indo-Pacific and Atlantic oceans through the 
Mediterranean and between the western Atlantic and 
eastern Pacific oceans through what is now Central 
America (Menon, 1977). If the species groups, as de- 
fined by ID patterns (Munroe, 1992), represent mono- 
phyletic assemblages, then not only was Symphurus 
in existence prior to closure of the seaways, but the 
genus had also undergone a significant level of diversi- 
fication because multiple species groups are shared 
across what are now land barriers. 
In the western Atlantic Ocean, species of Sym- 
phurus have an extensive distribution from Nova 
Scotia (ca. 45°N) to Argentina (ca. 45°S). Most spe- 
cies, however, are found in tropical and warm-tem- 
perate regions. All 24 western Atlantic species of 
Symphurus occur between 34°N and 25°S latitudes, 
with the greatest diversity in tropical and warm-tem- 
perate regions (10 and 12 species, respectively). At 
extremes of their geographic range in the western 
Atlantic, the diversity of tonguefishes is minimal (2 
and 3 species, respectively) compared with that in 
tropical and subtropical regions. Furthermore, no 
species occurring beyond temperate faunal bound- 
aries (Cape Hatteras in the north and Rio de la Plata 
in the south) are endemic to these regions. Adults of 
only two species (S. billykrietei and S. minor ) occur 
in boreal seas of the western North Atlantic, and only 
S. billykrietei is a permanent resident in this area. 
In the South Atlantic, the geographic limit for the 
genus is in the temperate seas off central Argentina 
(ca. 45°S), where only S. trewauasae is found. The 
geographical distribution of Symphurus in the east- 
ern Atlantic Ocean (Munroe, 1990), by comparison, 
is far less extensive to the south (from ca. 45°N to 
12°S) than that in the western Atlantic (ca. 45°N to 
45°S). Symphurus nigrescens, the most northerly oc- 
curring of the eastern Atlantic species, extends into 
the Bay of Biscay (ca. 45°N) but usually is more abun- 
dant farther south, especially near the entrance to, 
and in, the Mediterranean Sea, and off the coast of 
West Africa (to ca. 7°S). This species and S. ligulatus 
are the only symphurine tonguefishes found in the 
Mediterranean Sea. Two other species (S. normani 
and S. vanmelleae) occur on the continental shelf and 
slope off tropical Africa (to ca. 12°S). 
Geographic distributional patterns of marine or- 
ganisms have been well studied in the Atlantic 
Ocean. In the western North Atlantic, Cape Hatteras 
