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Rev. Biol. Trop. 49 Supl. 1. 177-185, 2001
A New Species of Trinectes (Pleuronectiformes: Achiridae), with
Comments on the other Eastern Pacific Species of the Genus
H. J. Walker, Jr. and John Bollinger*
Scripps Institution of Oceanography, University of California, San Diego 0208, La Jolla, CA92093-0208 USA. Ffax: (858)
534-5306. E-mail: hjwalker@ucsd.edu
*present address, JB: 1335 Ponderosa Drive, Moscow, Idaho 83843 USA
Abstract: A new eastern Pacific achirid, Trinectes xanthurus, has a distinctive yellow or light caudal fin, without pattern,
to contrast with its relatively dark body. This species also has black, posterior margins of the dorsal and anal fins and 21-
22 caudal vertebrae, versus 19-20 for its Pacific coast congeners. It usually is found in shallow, continental shelf waters on
sand or mud bottoms and ranges from Colombia to El Salvador. The genus Trinectes is represented in the eastern Pacific
by four species. A fifth species usually occurs in Pacific slope drainages (freshwater) in Panama. Of these species, only
Trinectesfonsecensis is found throughout the tropical eastern Pacific, while the other three coastal species are confined to
tropical waters south of the Golfo de Tehauntepec.
Key words: New species, Trinectes, Achiridae, Pleuronectiformes, Pisces, identification key
There are four species of the New World
genus Trinectes in the coastal waters of the
eastern Pacific: T. fimbriatus (Gunther), T.
fonsecensis (Gunther), T.opercularis (Nichols
& Murphy), and a new species, described
herein, T. xanthurus. An additional species, T.
fluviatilis (Meek & Hildebrand), appears to be
confined almost exclusively to freshwater, in
Pacific slope drainages in Panama and is
included in this analysis. The three congener-
ic species in the western Atlantic are T.
inscriptus (Gosse), T. maculatus (Bloch &
Schneider), and T. p a u l i s t a n u s ( R i b e i r o )
(Dawson 1978). In addition, T. maculatus, T.
xanthurus, T. paulistanus, and T. fonsecensis
occasionally occur in freshwater. This paper
describes the new species and provides char-
acters useful in distinguishing the eastern
Pacific species. Meristic tables, photographs,
and a key are provided as aids to identification
and to show variation.
MATERIALS AND METHODS
Counts and measurements generally fol-
low those of Hubbs & Lagler (1958). Verte-
bral and some caudal-fin ray counts were
made from radiographs. All pigmentation
notes were made from alcohol-preserved
specimens. Institutional abbreviations follow
Leviton et al. (1985). Standard length (SL) is
used thoughout unless otherwise stated.
Trinectes xanthurus, new species
(Fig. 1)
Trinectes sp. Krupp 1995: 847, 850.
Holotype: SIO 63-292, 75.4 mm, Panama, Bahia
Received: 10-VIII-2000 Corrected: 23-XI-2000 Accepted: 8-XII-2000
R E V I S TA DE BIOLOGIA T R O P I C A L178
SL, decreasing with increasing SL; upper eye
length 4.5-6.8% of SL, decreasing with
increasing SL. Scales ctenoid; enlarged scales
on anterior head region of ocular side,
enlarged scales and tufts of cirri over much of
head and area above pelvic fins on blind side;
scales along most of the lengths of the dorsal,
anal-, and caudal-fin rays. Anterior dorsal
(ca. 20-24) and anal- (ca. 8) fin rays of blind
side with cirri for most of their lengths. Pelvic
fins more or less symmetrical, that of ocular
side connected to anal fin by a thin mem-
brane; cirri on all pelvic-fin rays of blind side,
smaller cirri on anterior rays of ocular side.
Caudal fin rounded posteriorly. Lateral line
nearly straight on both sides, with a slight rise
over area of opercular opening. No cirri on
nostrils; cirri on lip of lower jaw, ocular side
only. Upper eye slightly in advance of lower.
Mouth small, reaching to a vertical through
anterior portion of lower eye; teeth tiny, villi-
form, in multiple rows in upper and lower
jaws of blind side; few, if any, teeth on ocular
side.
Overall background color of ocular side
light to medium brown, occasionally with 5-
11 thin, approximately vertical, interrupted
bars and numerous dark spots; dorsal and anal
fins without light or dark spots or blotches;
anterior dorsal and anal fins usually matching
body color; blind side usually almost devoid
of pigment, but occasionally with the posteri-
or one-third to one-half of body lightly to
moderately pigmented; posterior dorsal and
anal fins of both sides matching body color
San Miguel, ca 8
o
15’N, 78
o
25’W, 1959 (no other data
available).
Paratypes: 230 specimens (18.5-95 mm). Colom-
bia: UCLAW53-20 (1). Panama: SIO 63-292 (30); SIO
63-293 (23); SIO 63-295 (1); SIO 64-965 (3); SIO 69-
386 (5); UCLA W53-275 (28); UCLA W53-317 (4);
UCLAW58-55 (3); UCLAW58-304 (41); UCLAW58-
305 (40); LACM W53-331 (1); GCRL V72-9100 (1);
GCRL V72-9101 (2); GCRL V72-9106 (1); USNM
361978 (3), formerly SIO 63-292. Costa Rica: UCR
970.005 (12); UCR 136.083 (3); UCR 296.007 (7); UCR
1216.002 (1); LACM 9754-14 (1); LACM 30714-14 (3);
LACM 30715-4 (1); LACM 30716-6 (1); LACM 30745-4
(3); LACM 32542-6 (2); LACM 33805-27 (6). Nicaragua:
UCR 360.005 (1). El Salvador: SIO 73-276 (2).
Diagnosis: A relatively small species of
Tr i n e c t e s (maximum length examined, 95
mm) characterized by the following: caudal
fin yellow or light brown, without pattern;
posterior dorsal and anal fins black to dark
brown; dorsal-fin rays usually 57-60; anal-fin
rays usually 43-46; pelvic-fin rays usually 5-
5; caudal vertebrae usually 21-22; dorsal and
anal fins without light or dark spots or blotch-
es; pectoral fins usually absent; opercular flap
of blind side mostly scaled; no ring of cirri on
margin of anterior naris on ocular side.
Description: Dorsal-fin rays 54-61 (Table
1); anal-fin rays 41-48 (Table 2); vertebrae 8-
10 + 20-22 = 29-31, holotype with 9+21; total
caudal-fin rays 16, branched rays usually 12;
pelvic-fin rays 5-5 (186 of 198 specimens,
holotype with 5-5). Pectoral fins almost
always absent, occasionally one ray on ocular
side (6 of 198 specimens; holotype 0-0).
Body depth 53.1-63.2% of SL; head length
27.6-33.1% of SL, slightly increasing with
increasing SL; interobital width 2.5-4.1% of
TABLE 1
Frequency distributions of dorsal-fin rays in Pacific species of Trinectes.
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64
T. fimbriatus 5 6 12 31 34 17 12 4 2
T. fluviatilis 1 2 5 8 7 4 3
T. fonsecensis 1 6 19 42 54 69 50 30 20 10 1
T. opercularis 1 2 1
T. xanthurus 4 8 16 41 49* 47 21 12
* count of holotype.
I N T E R N AT I O N A L J O U R N A L OF T R O P I C A L B I O L O G Y AND CONSERVAT I O N 179
Fig. 1. Trinectes xanthurus, SIO 63-292, upper: 75.4 mm, Holotype; lower: 73 mm, Paratype.
R E V I S TA DE BIOLOGIA T R O P I C A L180
Distribution: From the mouth of the
Orapu River, Colombia, ca. 4°34’N,
77°20’W, to the Golfo de Fonseca, El Sal-
vador, ca.13°06’N, 87°59’W. Found on sand
or mud bottoms in rivers (occasionally) and
shallow coastal waters of 2-40 m, but usually
less than 18 m.
Comparisons: Trinectes xanthurus can
be distinguished from all other congeners,
except T. fluviatilis, in having 21-22 (vs. 19-
20) caudal vertebrae. It has a plain or unpat-
terned caudal fin in contrast to the banded
proximally, but much darker distally; caudal
fin pale yellow, yellow in life (Krupp 1995),
to light brown with no markings; pigmenta-
tion on ocular-side pelvic fin matching that on
anal fin, blind-side pelvic fin without pig-
ment; peritoneum and opercular cavity lightly
to moderatly punctate on ocular side and usu-
ally lacking pigment on blind side; mouth
devoid of pigment.
Etymology: From the Greek, x a n t h o s,
yellow, plus oura, tail, for the pale yellow or
light brown caudal fin.
Fig. 2. Trinectes fimbriatus, Uncatalogued, 71 mm total length, Chiapas, Mexico, 6 Sep 1966, showing a ring of cirri on
the margin of the anterior naris.
TABLE 2.
Frequency distributions of anal-fin rays in Pacific species of Trinectes.
33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
T. fimbriatus 1 3 16 33 41 21 6 2
T. fluviatilis 6 7 8 8
T. fonsecensis 1 7 27 56 85 66 37 20 5 1
T. opercularis 1 1 3
T. xanthurus 7 8 35 59* 62 19 4 3
* count of holotype.
181
Fig. 3. Trinectes fimbriatus, UCR 136.038, 6(60-68.5 mm), illustrating variation in this species.
I N T E R N AT I O N A L J O U R N A L OF T R O P I C A L B I O L O G Y AND CONSERVAT I O N
R E V I S TA DE BIOLOGIA T R O P I C A L182
Fig. 4. Trinectes opercularis, UCLAW51-283, 52.5 mm.
Key to the eastern Pacific species of Trinectes
1A. Ring of cirri on margin of anterior naris of ocular side (Fig. 2); anal-fin rays usually 35-38; opercular flap of blind
side mostly naked . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
1B. No cirri on anterior naris of ocular side; anal-fin rays usually 41-46; opercular flap of blind side mostly scaled .3
2A. Body and vertical fins with white or pale spots on ocular side . . .T. fimbriatus (Peru to Chiapas, Mexico; Fig. 3)
2B. Body and fins without spots, head occasionally with spots on posterior operculum . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .T. opercularis (Equador to Colombia; Fig. 4)
3A. Posterior dorsal and anal fins black to dark brown; caudal fin without distinct pigment pattern; pectoral fins usual-
ly absent (192 of 198 specimens) . . . . . . . . . . . . . . . . . . . . . . . . .T. xanthurus (Colombia to El Salvador; Fig. 1)
3B. Dorsal and anal fins spotted or light brown; caudal fin usually spotted or barred; pectoral fin, when present, with
one to three rays on ocular side . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
4A. Pectoral fin usually present (272 of 304 specimens); ocular side with fairly distinct, dark bars; caudal vertebrae 19-
20 (202 of 215 specimens) . . . . . . . . . . . . . . . . . . . . . . . .T. fonsecensis (Panama to Agiabampo, Mexico; Fig. 5)
4B. Pectoral fins usually absent (19 of 30 specimens); ocular side with indistinct, dark bars and small spots or large
blotches; caudal vertebrae 21 (16 of 17 specimens)
. . . . . . . . . . . . . . . . . . . . . . . . .T. fluviatilis (Panama to Costa Rica, almost always found in freshwater; Fig. 6)
183
Fig. 5. Trinectes fonsecensis, SIO 62-39, upper: 85 mm; lower: 84 mm.
I N T E R N AT I O N A L J O U R N A L OF T R O P I C A L B I O L O G Y AND CONSERVAT I O N
R E V I S TA DE BIOLOGIA T R O P I C A L184
Fig. 6. Trinectes fluviatilis, USNM 81668, 6(30-39 mm).
caudal-fin pattern of T. fluviatilis and also has
a greater body depth and smaller eyes.
Trinectes fimbriatus and T. opercularis have
fewer anal-fin rays than T. xanthurus and also
possess a ring of cirri on the margin of the
ocular-side anterior naris. Trinectes fimbria -
tus also has conspicuous white or pale spots
on its ocular side. In contrast to T. xanthurus,
T. fonsecensis usually has at least one or two
ocular-side pectoral-fin rays and pigment pat-
terns on the vertical fins. Trinectes inscriptus
(western Atlantic) is unique in having one or
more pectoral-fin rays on the blind side and at
least two, usually three or more, on the ocular
side. It also has a distinctive network of dark
lines on a brown to gray background.
Trinectes maculatus (wA) usually has 4-4 (vs.
5-5) pelvic-fin rays, distinguishing it from all
other species in the genus, and has a variable
pattern of caudal-fin pigment to distinguish it
further from T. xanthurus. Trinectes paulis -
tanus (wA) can appear quite similar to T. xan -
thurus, but has much smaller eyes, and usual-
ly a shorter head, shallower body depth, and
narrower interorbit.
ACKNOWLEDGMENTS
We are grateful to Carl L. Hubbs
(deceased) for instigating this study.We thank
the following individuals for the loan of spec-
imens and/or for correspondence related to
this study: W. Bussing (UCR), D. Buth
(UCLA), R. Feeney and J. Seigel (LACM), S.
Poss and C. Aadland (GCRL), N. Wilimovsky
(UBC), D. Catania (CAS), S. Jewett and J.
Williams (USNM). We appreciate the timely
185
data supplied by W. Bussing and D. Buth and
the photo in Figure 3 provided by W. Bussing.
This paper is dedicated to S. Walker, J. Walk-
er, T. Walker, B. Walker, and D. Walker for
inspiration and support. We thank P. Hastings,
R. Rosenblatt, and C. Klepadlo for assistance
at SIO. This paper is also dedicated to T.
Collins, Deputy Director of SIO, for his
unwavering support of the SIO Marine Verte-
brates Collection.
RESUMEN
Se describe una nueva especie, Trinectes xanthuru s,
de aguas someras del Pacífico desde Colombia hasta El
S a l v a d o r. El género Tr i n e c t e s tiene cuatro especies en
el Pacífico Oriental más una de agua dulce en Panamá.
Solo Trinectes fonsecensis existe en todo el Pacífico
O r i e n t a l .
REFERENCES
Dawson, C.E. 1978. Soleidae. In W. Fischer (ed.). FAO
species identification sheets for fishery purposes.
Western Central Atlantic (Fishing area 31). vol. V.
FAO, Rome.
Hubbs, C.L. & K.F. Lagler. 1958. Fishes of the Great
Lakes region. Cranbrook Inst. Sci. Bull. No. 26,
Bloomfield Hills, Michigan.
Krupp, F. 1995. Achiridae. p. 845-850. In W. Fischer, F.
Krupp, W. Schneider, C. Sommer, K. E. Carpenter &
V. H. Niem (eds.). Guía FAO para la identificación
de especies para los fines de la pesca. Pacífico Cen-
tro-Oriental. FAO, Roma.
Leviton, A.E., R.H. Gibbs, Jr., E. Heal & C.E. Dawson.
1985. Standards in herpetology and ichthyology. Part
I. Standard symbolic codes for institutional resources
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