Redescription of the Dwarf Neotropical Eleotrid Genus Leptophilypnus(Teleostei: Gobioidei), Including a New Species and Commentson Microphilypnus

Abstract

Among the eight genera of Eleotridae known from the Neotropics, two, Microphilypnus and Leptophilypnus, are greatly reduced in size and, along with the Australian genus Philypnodon, form a separate phylogenetic radiation from the other six genera. Microeleotris was described with Leptophilypnus, but Hildebrand later placed the two in synonymy. The original descriptions for these taxa were brief and did not include illustrations. As a result, confusion exists, particularly with regard to the identity of the three described species of Microphilypnus: M. ternetzi, M. amazonicus, and M. macrostoma. Three valid species of Leptophilypnus are known: L. fluviatilis, L. panamensis, and a new species from the Gulf of Mexico drainages of Guatemala that is described herein. Microphilypnus is diagnosed and new information is offered on types of the three nominal species and the habitat characteristics of the genus.

Full text

Redescription of the Dwarf Neotropical Eleotrid Genus Leptophilypnus
(Teleostei: Gobioidei), Including a New Species and Comments
on Microphilypnus
CHRISTINE E. THACKER,FRANK PEZOLD,AND ROYAL D. SUTTKUS
Among the eight genera of Eleotridae known from the Neotropics, two,
Microphilypnus and Leptophilypnus, are greatly reduced in size and, along with the
Australian genus Philypnodon, form a separate phylogenetic radiation from the other six
genera. Microeleotris was described with Leptophilypnus, but Hildebrand later placed the
two in synonymy. The original descriptions for these taxa were brief and did not
include illustrations. As a result, confusion exists, particularly with regard to the
identity of the three described species of Microphilypnus:M. ternetzi,M. amazonicus, and
M. macrostoma. Three valid species of Leptophilypnus are known: L. fluviatilis,L.
panamensis, and a new species from the Gulf of Mexico drainages of Guatemala that is
described herein. Microphilypnus is diagnosed and new information is offered on types
of the three nominal species and the habitat characteristics of the genus.
ELEOTRIDAE (gudgeons or sleepers) is
a family of 30 genera and approximately
135 species, distributed primarily throughout the
fresh and brackish waters of the old world tropics
(Birdsong et al., 1988; Hoese and Gill, 1993).
Eight eleotrid genera inhabit the Neotropics,
and of those, two genera are distinctive in that
they are reduced in size and are placed in a clade
(together with the Australian genus Philypnodon)
separate from the remaining genera (Thacker
and Hardman, 2005). These dwarf genera,
Leptophilypnus and Microphilypnus, do not overlap
in distribution; Leptophilypnus is known from
drainages on both coasts of Central America,
Microphilypnus from Atlantic and Caribbean
drainages of South America only. Few collections
are available for either genus, and their system-
atics have not been examined since the various
works of the original authors. In this study, we
clarify the descriptions of both genera and
include figures, examine and evaluate species
identity based on museum collections, describe
a new species of Leptophilypnus, and provide
additional information on the ecology of both
genera.
MATERIALS AND METHODS
Museum specimens as listed below were
examined with a dissecting microscope and
photographed with Nikon Coolpix 8700 and
Sony DSC-F717 digital cameras. Radiographs
were taken with a Faxitron 43855c cabinet x-ray
machine using Kodak industrex M film. Images
used for neuromast illustrations were captured
using a Leica MZ 12.5 imaging station with an
Evolution LC digital camera and Image Pro
Express and drawn with CorelDRAW 11. Counts
of meristic characters were taken from radio-
graphs and cleared-and-stained specimens; fre-
quently in these small fishes the fin rays were so
tiny that determination of fin element number
was best accomplished by counting pterygio-
phores. First dorsal-fin pterygiophore insertion
patterns are denoted per the formula given by
Birdsong et al. (1988): the first digit indicates the
interneural space where the first pterygiophore is
located, the digits following the dash indicate
how many pterygiophores are found in each
succesive interneural space, up to the start of the
second dorsal fin. Thus, a formula of 3-12210
indicates that one pterygiophore is present in the
third interneural space, two in the fourth, two in
the fifth, one in the sixth and none in the
seventh; the eight interneural space is where the
second dorsal fin begins. Vertebrae are pre-
sented as precaudal+caudal5total, where pre-
caudal vertebrae are those without a closed
haemal arch (following Birdsong et al., 1988).
The caudal vertebral count includes the terminal
vertebral element, which in these species is fused
to the hypurals. Cephalic lateralis canal pores are
identified using the lettering system of Akihito et
al. (1984) and Pezold (1993). Cephalic free
neuromast patterns are described using termi-
nology developed by Sanzo (1911) with modifica-
tions employed by Miller and Wongrat (1991).
Transverse suborbital rows are designated with
Arabic numbers and major horizontal rows on
the cheek are indicated with the letters b and d.
Transverse opercular rows are labeled ot and ot9,
upper and lower longitudinal rows on the
operculum are labeled os and oi, respectively.
Institutional abbreviations are as listed in Leviton
Copeia, 2006(3), pp. 489–499
#2006 by the American Society of Ichthyologists and Herpetologists

et al. (1985). Other abbreviations: radiograph
(x); cleared and stained (CS); standard length
(SL).
Mensural data were obtained with digital
calipers and a dissecting microscope. Measure-
ments taken were standard length (tip of the
snout not including the jaw to the base of the
caudal fin), head length (tip of the snout not
including the jaw to the upper posterior corner
of the bony opercle), head width (greatest width
at preopercle), jaw length (from tip of lower jaw
to angle of the jaws), eye length (longitudinal
diameter of eye), interorbital width (least dis-
tance between left and right orbits), caudal-
peduncle length (distance from insertion of last
anal-fin ray to midpoint of caudal-fin base),
second dorsal-fin length (origin of second dorsal
fin to appressed tip of last ray), anal-fin length
(anal-fin origin to appressed tip of last ray),
pectoral-fin length (from base to tip of longest
ray), pelvic-fin length (from base to tip of longest
ray), and caudal-fin length (base to tip of longest
ray). Meristic data included lateral scale rows
(number of rows from posterodorsal tip of
opercle to base of caudal fin, not counting scales
on caudal fin), transverse scale rows (number of
scale rows along diagonal from anal-fin origin to
base of second dorsal fin), caudal-peduncle rows
(number of scale rows along diagonal from
insertion of last anal-fin ray to middorsal line of
caudal peduncle), predorsal scales (number of
scale rows along nape midline anterior to first
dorsal-fin origin), pectoral-fin ray number, sec-
ond dorsal-fin elements (last ray counted as one
if split), anal-fin rays (last ray usually split and
counted as one), and caudal-fin rays (the
number of segmented but unbranched, and
segmented and branched rays).
Leptophilypnus Meek and Hildebrand, 1916
Leptophilypnus Meek and Hildebrand, 1916:361
(type species: Leptophilypnus fluviatilis Meek
and Hildebrand, 1916, by original designation
and monotypy.)
Microeleotris Meek and Hildebrand, 1916:362
(type species: Microeleotris panamensis Meek
and Hildebrand, 1916, by original designation
and monotypy).
Diagnosis.—Species of the genus may be distin-
guished from all other Eleotridae by the follow-
ing combination of characters. Mouth large and
oblique with prominent lower jaw; no preoper-
cular spine; no spines on first or second
branchiostegal rays; no serrations on bony
supraorbital ridge; eyes dorsolateral; interorbital
not wider than eye diameter; gill opening
extending forward nearly to vertical from poste-
rior margin of eye; infraorbital free neuromasts
present in transverse rows; transverse rows of free
neuromasts above pectoral-fin base and midlat-
erally on trunk, at least one very long row
beneath pectoral-fin base that extends onto
upper abdomen; three roughly parallel rows of
free neuromasts on caudal fin extending from
base to posterior margin; six spines in first dorsal
fin; head, predorsal, and prepelvic regions
without scales; scales on trunk ctenoid with 30–
36 scales in a longitudinal series.
Description.—Head large, about 27–34%SL;
lower jaw prominent; anterior nares short tubes
overhanging edge of snout, posterior nares
small open pits; fleshy interorbital narrow,
smaller than eye diameter; eyes dorsolateral;
tongue truncate, slightly bilobed; teeth small
highly recurved canines in several rows forming
bands in both jaws; no teeth on vomer; gill
membranes approach closely but do not meet
across isthmus, opening reaches forward to
vertical through posterior margin of eye; dorsal
fins widely spaced; first dorsal fin with six spines,
the last spaced more distantly than the remain-
der; second dorsal fin with one spine and seven
to nine soft rays; anal fin with one spine and
seven to nine soft rays; second dorsal-fin,
pectoral-fin, and anal-fin rays branched distally;
pelvic fins separate, each with one spine and five
soft rays; pectoral-fin rays reaching to vertical
through second dorsal- and anal-fin origins;
appressedseconddorsalandanalfinsnot
reaching caudal-fin base; caudal fin with 2–4
segmented and 11–13 branched rays; vertebrae
10 +16–17 526–27; genital papilla present in
both sexes; small size, less than 55 mm standard
length.
Remarks.—In Meek and Hildebrand’s (1916)
original description, they distinguished the gen-
era Leptophilypnus and Microeleotris by the extent
to which the dentary bones were expanded
medioventrally on the underside of the jaw. They
state in the diagnosis of Leptophilypnus: ‘‘dentary
bones meeting under posterior angle of mouth,
leaving an oval-shaped naked area at chin . . .
readily distinguished from all other Eleotridinae
by the broad and expanded dentary bones’’. In
a later analysis, Hildebrand (1938) examined
additional specimens of both genera and con-
cluded that the degree of dentary expansion
varied continuously from one to the other, and
so placed the two genera in synonymy, placing M.
mindii in synonymy with L. fluviatilis,and
reassigning M. panamensis to Leptophilypnus.
490 COPEIA, 2006, NO. 3

Leptophilypnus fluviatilis Meek and Hildebrand,
1916
Figure 1
Leptophilypnus fluviatilis Meek and Hildebrand,
1916:361–362 (type locality very muddy brack-
ish creek, Mindi, Canal Zone, Panama; holo-
type FMNH 8952).
Microeleotris mindii Meek and Hildebrand,
1916:364 (type locality muddy brackish creek,
Mindi, Canal Zone, Panama; holotype FMNH
8954.)
Diagnosis.—ALeptophilypnus with dorsal pterygio-
phores 3–12210; second dorsal-fin elements I, 9;
anal-fin elements I, 9; pectoral-fin rays 18–19;
segmented rays in caudal fin 2 segmented +11
(rarely 12) branched +2 (rarely 1); vertebrae 10
+16 526; ot9free neuromast row present on
opercle (Fig. 2); cephalic lateralis canals present
with pores ‘BDF’‘KL’‘MNO’ (pore N lost on one
side in at least one specimen examined); jaws
reaching vertical through anterior third or mid-
dle of eye; prominent basicaudal spot present.
Description.—Six or seven short gill rakers on the
lower portion of the first gill arch, not over-
lapping when appressed; generally no predorsal
scales, occasionally one or two present at base of
first dorsal-fin origin; scales in longitudinal series
28 to 32; 7–9 transverse scale rows; 6–7 transverse
caudal-peduncle scale rows. Jaws reaching poster-
iorly only as far as a vertical through the anterior
third or middle of the eye; head dorsoventrally
compressed, width at preopercle moderate,
averaging less than 1/3 head length; second
dorsal-fin and anal-fin origins equal; first dorsal-
fin spines not elongate, not reaching second
dorsal-fin origin; pectoral fins reaching vertical
between second dorsal- and anal-fin origins;
pelvic fins not reaching anal-fin origin; urogen-
ital papillae longer and thinner in males than
females, truncate in both. Body proportions
given in Table 1.
Coloration in alcohol.—Description based primarily
upon GCRL 7850 and GCRL 12147. Ground
color (of preserved specimens) pale tan, with five
prominent midlateral dark blotches, originating
under pectoral fin and terminating at caudal
peduncle, basicaudal blotch darkest. Four dark
saddles across dorsal midline, offset from lateral
blotches. Nape and head mottled; head pigment
includes two diagonal slashes, one extending
strap-like from eye forward across jaws just
behind tip of lower jaw, continuous with band
crossing chin, another behind eye, extending
from rear margin of mouth to top of preopercle,
and a vertical bar running from the lower margin
of the eye to the end of the lower jaw. First dorsal
fin with prominent diagonal band just above
base, second dorsal fin with several bands more
or less parallel to fin base, anal fin dusky in
males, unpigmented in females. Pair of spots
present on upper and lower pectoral-fin base
with a few melanophores extending onto fin
membrane, thin edging of pigment along fin
rays, otherwise clear. Pelvic fin unpigmented in
females and small males, becoming dusky in
maturing males. Caudal fin with four or five
vertical bars in some specimens.
Remarks.—Distinguished from L. panamensis by
possession of one more soft dorsal-fin and anal-
fin ray, caudal-fin rays usually 2 +11 +2, and
a forked row of sensory neuromasts on the
opercle (ot9present). Distinguished from the
Fig. 1. Leptophilypnus fluviatilis, UMMZ 199560, 31.8–36.6 mm SL. Scale bar 55 mm.
THACKER ET AL.—SYSTEMATICS OF LEPTOPHILYPNUS 491

new species in having a prominent rectangular or
triangular basicaudal blotch rather than a narrow
bar at caudal-fin base, row ot9present on the
opercle, 18 or 19 pectoral-fin rays, second dorsal-
and anal-fin origins equal, larger jaws, and
cephalic lateralis canals present.
Distribution.—Estuaries of Atlantic drainages of
Central America, Honduras to Panama. Most
specimens have been taken from Panama.
Although not included by Bussing (1998) as
a component of the freshwater ichthyofauna of
Costa Rica, six specimens of L. fluviatilis have
been recorded from the Tortuguero estuary
(Gilbert and Kelso, 1971).
Leptophilypnus panamensis
(Meek and Hildebrand, 1916)
Figure 3
Eleotris macrolepis Meek, 1914:130–131 (not of
Bleeker, 1875) (type locality Jesus Maria, Costa
Rica; holotype FMNH 7775)
Microeleotris panamensis Meek and Hildebrand,
1916:363 (type locality Rio Juan Diaz, Panama;
holotype FMNH 8953)
Diagnosis.—ALeptophilypnus with first dorsal-fin
pterygiophore formula 3-12210; second dorsal-
fin elements I, 8; anal-fin elements I, 8; pectoral-
fin rays 17–20 (usually 18 or 19); caudal fin with
2 segmented (occasionally 1) +12 (occasionally
13) branched +1 segmented rays; vertebrae
9–10 +16–17 525 (one specimen with 9 +17),
no ot9free neuromast row on opercle (Fig. 2);
cephalic lateralis canals present with pores
‘BDF’‘KL’‘MNO’; jaws reaching vertical through
mideye in females, posterior margin of eye in
males; basicaudal spot present.
Description.—Four or five short gill rakers on the
lower portion of the first gill arch, not over-
lapping when appressed; generally no predorsal
scales, occasionally one to three present at base
of first dorsal-fin origin; scales in longitudinal
series 31–33; 8–10 (usually 8) transverse scale
rows; 6–8 (usually 7) transverse caudal-peduncle
scale rows. Jaws reaching posterior to a vertical
through mideye in females, to rear margin of eye
in males; head broad and dorsoventrally com-
pressed, width at preopercle usually greater than
half head length; second dorsal-fin and anal-fin
origins equal; first dorsal-fin spines not elongate,
not reaching second dorsal-fin origin; pectoral
fins reaching vertical between second dorsal- and
anal-fin origins in males, just shy of vertical in
females; pelvic fins usually not reaching anus,
longer in males than females; urogenital papillae
long, thin and truncate in males, broad and
triangulate in females. Body proportions given in
Table 1.
Coloration in alcohol.—Based primarily upon TU
25132 and AMNH uncat. Body brown dorsally
becoming light tan ventrally and on abdomen.
Three to six dark vertical streaks beneath
pectoral fins. Four indistinct saddles across
dorsal midline, one beneath first dorsal fin, two
beneath posterior two-thirds of second dorsal fin,
one on caudal peduncle at base of caudal fin.
Small scattered melanophores peppering trunk,
nape, and head. Brown spots on trunk, co-
alescing in some to form four or five indistinct
midlateral blotches, last forming a basicaudal
Fig. 2. Stylized infraorbital and opercular free
neuromast rows of (A) Leptophilypnus fluviatilis,
(B) L. guatemalensis,(C)L. panamensis,and
(D) Microphilypnus ternetzi. Neuromast rows and
visible cephalic lateralis canal pores labelled.
492 COPEIA, 2006, NO. 3

spot. Midanterior opercle dark. Pectoral fins with
about nine vertical bars. Pelvic fins with some
speckling in females suggesting bars, dusky in
males. First dorsal fin with dark base in females,
about three diagonal bars. First dorsal fin in
males with dark margin, medial dark wishbone-
shaped diagonal band. Second dorsal fin with
about five diagonal bands formed from spots
largely restricted to elements in females but also
on interradial membranes in males. Anal fins in
females with elements edged in melanophores,
clear interradial membranes; dusky in males with
a dark submargin and light margin. Caudal fin
with about seven vertical bars formed from spots
with two or three dark spots on dorsal margin
near base, duskier in males than females.
Distribution.—Tidal freshwater of Pacific slope of
Panama and Costa Rica.
Remarks.—Distinguished from congener L. flu-
viatilis by the possession of one fewer dorsal- and
anal-fin rays, greater head width, lack of the ot9
sensory neuromast row on opercle, and number
of segmented and branched caudal-fin rays.
Distinguished from the new species by a di-
amond-shaped basicaudal spot rounded at the
posterior margin, rather than a narrow bar,
presence of cephalic lateralis canals, greater
head width, larger jaws, and 18–19 pectoral-fin
rays.
Grey (1947:142) noted that Isaac Ginsburg
examined the type of Eleotris macrolepis Meek,
TABLE 1. STANDARD LENGTHS AND PROPORTIONAL MEASUREMENTS FOR SPECIES OF Leptophilypnus (MEAN AND STANDARD
DEVIATION). First four proportions of head length, others proportions of SL. SL reported as measured value.
L. fluviatilis L. panamensis L. guatemalensis
mean SD nmean SD nmean SD n
Head width 0.31 0.04 20 0.57 0.06 15 0.30 0.03 20
Jaw length 0.26 0.03 22 0.42 0.10 17 0.18 0.03 20
Eye length 0.15 0.02 22 0.19 0.03 17 0.12 0.01 20
Interorbital 0.07 0.02 22 0.12 0.03 17 0.06 0.01 20
Head length 0.32 0.01 22 0.30 0.01 17 0.29 0.01 20
CPD length 0.28 0.02 13 0.26 0.01 15 0.29 0.01 20
Pectoral length 0.25 0.02 21 0.24 0.01 15 0.28 0.02 20
Pelvic length 0.20 0.01 21 0.18 0.01 17 0.21 0.01 20
Caudal length 0.27 0.02 20 0.25 0.02 15 0.28 0.01 20
2
nd
dorsal length 0.30 0.04 20 0.32 0.03 15 0.30 0.03 20
Anal-fin length 0.30 0.03 20 0.31 0.02 15 0.28 0.02 20
SL 34.44 3.73 22 46.33 6.75 17 29.10 2.22 20
Fig. 3. Top: Leptophilypnus panamensis, TU 25132, 44.6 mm SL. Scale bar 55 mm. Bottom: Leptophilypnus
guatemalensis, UMMZ 245081, holotype, 36.6 mm SL. Scale bar 55 mm.
THACKER ET AL.—SYSTEMATICS OF LEPTOPHILYPNUS 493

1914 and ‘‘found it identical with L. panamensis.’’
Another species (Culius macrolepis Bleeker, 1875,
revised to Eleotris by Weber, 1908) preoccupies E.
macrolepis, but E. macrolepis Meek, 1914 is simply
reassigned to the available name L. panamensis.
We follow this conclusion.
Leptophilypnus guatemalensis, new species,
Thacker and Pezold
Figure 3
Holotype.—UMMZ 245081 (ex UMMZ 197087),
male, 36.6 mm SL, Guatemala, Huehuetenango,
Rio San Ramon, ca. 300 m below outfall from
underground, elev. 240 m, Rio Ixcan drainage, 3
April 1974, D. E. Rosen and R. M. Bailey.
Paratypes.—UMMZ 197087 (32); LACM 56288-1
(2), female, 38.3 mm SL and male, 32.0 mm SL;
FMNH 116467 (2), 33.8–35.4 mm SL; NLU
78593 (2), 29.5–30.7 mm SL. All with same
locality information as holotype.
Diagnosis.—ALeptophilypnus with first dorsal-fin
pterygiophore formula 3-12210 or 3-12201 (rare-
ly 3-22110 or 3-22101); second dorsal-fin ele-
ments I, 7–9, usually I, 8; anal-fin elements I, 7–8,
usually I, 7; pectoral-fin rays 14 or 15; caudal fin
generally with 1 segmented +13 branched +1
segmented ray; vertebrae 10 +16–17 526–27;
opercular free neuromast row ot9absent (Fig. 2);
cephalic lateralis canals absent; jaws reaching
vertical through anterior margin of eye; thin
basicaudal bar, sometimes separated into two
thin vertical dashes. Distinguished from L.
fluviatilis and L. panamensis by: pigment forming
a narrow bar at base of caudal fin, rather than
a diamond or rectangular spot; fewer than 17
pectoral-fin rays (usually 14 or 15); no cephalic
lateralis canals; small jaws not reaching posterior
to the anterior margin of the eye; first dorsal-fin
spines not elongate, not reaching second dorsal-
fin origin in females, may reach just beyond
second dorsal-fin origin in males; and second
dorsal-fin origin anterior to anal-fin origin.
Description.—Four or five short gill rakers on the
lower portion of the first gill arch, not over-
lapping when appressed; no predorsal scales; 26
to 31 scales in longitudinal series; 8 transverse
scale rows; 7 transverse caudal-peduncle scale
rows. Jaws reaching posteriorly to a vertical
through anterior margin of eye; head dorsoven-
trally compressed, width moderate, 26–35%head
length at preopercle; anal-fin origin slightly
posterior to second dorsal-fin origin, about equal
to placement of first segmented ray of second
dorsal fin; first dorsal-fin spines not elongate,
reaching near second dorsal-fin origin in most,
reaching just beyond second dorsal-fin origin in
some males; pectoral fins reaching vertical
between second dorsal-fin and anal-fin origins;
pelvic fins not reaching anus; urogenital papillae
long and truncate, thin in males, broad and
truncate in females (width 2/3–3/4 length).
Body proportions given in Table 1.
Coloration in alcohol.—Based upon UMMZ 144145
and UMMZ 197094. Ground color pale tan, with
fairly uniform distribution of tiny dark spots on
head, dorsal and lateral surfaces, scales laterally
with brownish posterior margins, merging in
some to form indistinct reticulate pattern with
a variable number of midlateral paired X-shaped
concentrations. Spot present on side of nape at
upper corner of opercle. A thin vertical bar or
two thin disconnected but aligned vertical dashes
on caudal peduncle at base of caudal fin. Thin
dark line or lines variably developed midventrally
on caudal peduncle. In females usually a pair of
spots, one above the other, on pectoral-fin
support and a spot as large as pupil on upper
pectoral fin near dorsobasal margin usually with
no other pigment on pectoral fin; in males tiny
melanophores are more generally distributed on
pectoral fins and do not form prominent spots as
described for females. Pelvic fins unpigmented in
females, dusky in males. Anal fin sometimes
lightly pigmented in females, dusky in males.
First dorsal fin with broad dark margin separated
from wide dark diagonal band by broad unpig-
mented band, dark diagonal band beginning just
above unpigmented base of first spine. Second
dorsal fin with four or five diagonal rows of spots.
Caudal fin with spots forming about six vertical
bands.
Distribution.—Known from inland rivers of Gua-
temala in the Usumacinta watershed that drains
into the Gulf of Mexico west of the Yucatan
peninsula.
Remarks.—At this time we are unable to polarize
unique character states associated with the dwarf
Neotropical eleotrid species, but can associate
the new species with Leptophilypnus based on
overall similarity of different aspects of body
form, meristic features, pigmentation, and free
neuromast patterns.
Etymology.—This species is named for the col-
lection localities, all in the states of Hue-
huetenango, Quiche, or Alta Verapaz, Guate-
mala.
494 COPEIA, 2006, NO. 3

Microphilypnus Myers, 1927
Figure 4
Microphilypnus Myers, 1927:133–135 (type species:
Microphilypnus ternetzi Myers, 1927 by original
designation).
Diagnosis.—Prominent diagnostic characters of
the genus provided by Myers (1927) include: gill
openings extending forward to below posterior
border or center of pupil; isthmus moderately
narrow; vomerine teeth apparently absent; skull
without ridges posteriorly, slightly ridged or
irregular anterior to orbits; interorbital very
narrow; head and snout more or less elongate;
lower jaw projecting; scales large; opercles and
occiput scaled; cheeks and breast naked; size
minute. Additional diagnostic characters in-
clude: first dorsal fin with six spines, the last
spaced more distantly than the remainder;
dorsal-fin formula 3-22110, 3-21210 (Birdsong
et al., 1988) and possibly 3-221100; second dorsal
fin with one spine and seven or eight soft rays;
anal fin with one spine and seven or eight soft
rays, the last split to its base but counted as
a single element; vertebrae 11–13 +15–17 527–
28; genital papilla present in both sexes; gill
membranes approach closely but do not meet
across isthmus; pelvic fins separate, each with one
spine and five soft rays; four or five very short
transverse infraorbital rows of free neuromasts;
a single diagonal row of free neuromasts on
posterior field of opercle (Fig. 2).
Pale ground color, with scattered melano-
phores over entire body, concentrated in a diffuse
series midlaterally; dorsal, caudal, and anal fins
also stippled with melanophores; pectoral and
pelvic fins dusky but otherwise unmarked;
distinct line of melanophores at ventral midline;
minute size, less than 40 mm standard length.
Remarks.—When Myers (1927) described Micro-
philypnus, he included three species: M. amazoni-
cus,M. macrostoma, and M. ternetzi. At the time, he
expressed doubts about the placement of both
M. amazonicus and M. macrostoma, indicating in
his description of M. amazonicus (p. 135) that
‘‘this species and the next are probably not
congeneric with M. ternetzi or with each other,
but I hesitate to erect new genera on the poor
material available.’’ Our examination of types
and additional specimens of Microphilypnus does
not support Myers’ (1927) concern.
The holotypes of both Microphilypnus amazoni-
cus (CAS 76819 [formerly IU 17703], Igarape do
Mai Joana, Manaus, Brazil) and M. macrostoma
(CAS 76820 [formerly IU 17704], Igarape do Mai
Joana, Manaus, Brazil) are tiny, discolored, and
shrunken. Although pigmentation is poorly pre-
served, both types have a pigmented ventral
midline on the caudal peduncle as seen in M.
ternetzi. Also as observed in the syntypes of M.
ternetzi (CAS 76818 [2; formerly IU 17702] Cano
de Quiribana near Caicara, Venezuela), both
specimens have 13 pectoral-fin rays, 5–7 large
predorsal scales, fewer than 30 large scales in
a longitudinal row, and a jaw extending to below
mideye. Contrary to the Myers’ report (1927),
the holotype and other specimens of M. amazo-
nicus collected by Ternetz (CAS 76108 [1],
17.5 mm SL, Rio Negro, Cucuhy (Sto. Antonio)
Brazil; CAS 76109 [1], 16.1 mm SL, Rio Negro,
Cucuhy, Columbian border, Brazil) and the
holotype of M. macrostoma do not have a spine
on the ventral side of the preopercle, below the
eye, a feature synapomorphic for the Eleotris and
Erotelis clade (Pezold and Cage, 2002). Also in
contradiction to Myers’ (1927) description, there
is no evidence of a lateral line in the type and
only known specimen of M. macrostoma. Types of
Fig. 4. Top: Microphilypnus ternetzi, FMNH 110190, 34.7 mm SL. Scale bar 55mm. Bottom:
Microphilypnus ternetzi, showing live coloration. Size not recorded.
THACKER ET AL.—SYSTEMATICS OF LEPTOPHILYPNUS 495

all three nominal species possess a urogenital
papilla, a feature characteristic of Gobioidei but
rare among other percomorphs ( Johnson and
Brothers, 1993).
Myers (1927) reported the M. macrostoma
holotype to have a first dorsal fin with five spines,
and a second dorsal fin and anal fin each with
ten elements. Our observations indicate that
there are six spines in the first dorsal fin and
that the anal fin has nine elements. The body in
the vicinity of the second dorsal fin has been
damaged making a count difficult, but it may
contain ten elements as observed by Myers. The
shape of M. macrostoma is atypical: the lower jaw
protrudes more noticeably beyond the upper jaw
than as seen in other Microphilypnus, and the
body is greatly compressed laterally. Close in-
spection of the jaws suggests that the upper jaw
may be malformed. Radiographs also reveal
a significant curvature of the spine for the
specimen which may have contributed to the
increased body depth posteriorly, but the spec-
imen is torn and appears to have been smashed–
perhaps during capture. Whether this unique
representative of M. macrostoma represents a valid
taxon or an accidental anomaly, it is nonetheless
a specimen of Microphilypnus.
DISCUSSION
The two dwarf eleotrid genera, Leptophilypnus
and Microphilypnus, are widespread in the Neo-
tropics. Leptophilypnus is recorded from Central
America, including Guatemala, Panama, Hon-
duras, and Costa Rica. Information on the
ecology of Leptophilypnus panamensis comes pri-
marily from collection notes. This species was
collected by Meek and Hildebrand (1916:363),
‘‘in fresh water, not far above the head of tide, in
the Rio Chorrera near Chorrera and in the Rio
Juan Diaz at Juan Diaz on the Pacific slope.’’ It
was similarly taken in 1961 by one of the authors
(RDS) in fresh water not far from the outlet of
Rio Baru and in the lower Rio Grande de Terraba
in Costa Rica in 1962. Both streams were white
water. Substrates were boulder and rubble in Rio
Baru and sand and mud in Rio Grande de
Terraba. Vegetation was absent in Rio Baru and
limited to very little along the shore of the Rio
Grande de Terraba. Collections along steep
sandy and rocky shore of a tidal pass at the
mouth of the Rio Baru and 4 km north of
Dominical did not find the species. The apparent
absence at two sites on the lower Rio Baru could
reflect a very restricted habitat association or
differences in collection methods. Rotenone was
used 1 km N of Dominical, while 3-m seines were
used at the other two sites.
While Leptophilypnus panamensis seems to in-
habit tidal freshwater, L. fluviatilis appears to be
a more estuarine species. They are reported from
a muddy brackish creek on the Atlantic versant of
Panama in the Canal Zone (Meek and Hildeb-
rand, 1916, as L. fluviatilis and Microeleotris
mindii). Gilbert and Kelso (1971) collected six
specimens from the Tortuguero Lagoon estuary.
One collection site was characterized by open
shallow bays 0.6 m or less in depth with a bottom
varying from open to having filamentous algae
and some submerged vegetation. The other site
had a narrow shoreline with a steep slope and few
shallows. This shore had much emergent, sub-
merged, and floating vegetation. The new spe-
cies, L. guatemalensis, is strictly a freshwater
species, being known only from the upper
Usumacinta River basin in Guatemala.
Microphilypnus also may be restricted to fresh-
water and has been recorded from throughout
the Amazon and Orinoco drainages in Brazil,
Venezuela, Colombia, Bolivia, and Guyana. Re-
cent collections have yielded information on the
habitat of this taxon (Mark Sabaj, pers. comm.).
The M. ternetzi photographed in Figure 4 was
collected in Guyana, 10 km northeast of Lethem,
in the Manari River (clear to weakly blackwater).
The collection was made by seining during the
low water season, in calm shallows near the bank
of the river (approximately 3–6 m in depth), over
a substrate of sand and mud/silt among vegeta-
tion. Microphilypnus have also been captured
from the Rio Negro (blackwater) in Amazonas,
7.2 km northwest of San Carlos do Rio Negro, by
similar methods. At this locality numerous speci-
mens were found after sunset at the tail end of
a small, narrow but deep (over 2 m), backwater
with steep banks and a sand/silt substrate
without vegetation. The backwater opened di-
rectly into the Rio Negro and was separated from
this large channel by a long, narrow spit of sand.
Specimens were not found on the channel side
of the spit where the substrate was entirely sand
and current was moderate. Another recent
collection of Microphilypnus is from the Rio Yutaje
upstream from the mouth of the Rio Manapiare
(Ventuari- Orinoco drainage), Amazonas, Vene-
zuela. At this site the river expanded into a large
shallow lake (clear to weakly blackwater) with
abundant marsh habitat. Microphilypnus were
common among submerged vegetation in shal-
low still water (less than 0.6 m) over a substrate
of sand and mud/silt.
MATERIAL EXAMINED
Leptophilypnus fluviatilis.—CAS 6822 (4), Panama,
Canal Zone, Gatun Locks, upper chamber. CAS
496 COPEIA, 2006, NO. 3

124774 (2), Panama, Chagres River. Paratypes of
L. fluviatilis: FMNH 8569 (1), FMNH 8570 (1),
FMNH 8571 (1), FMNH 8572 (1), FMNH 8573
(1), FMNH 8574 (1), FMNH 8575 (1, c), FMNH
8576 (1), FMNH 8577 (1), FMNH 8578 (1, CS),
FMNH 8579 (1), FMNH 8581 (1), FMNH 8582
(1), FMNH 8583 (1, CS), FMNH 8584 (1),
FMNH 8585 (1), FMNH 8586 (1), FMNH 8587
(1), FMNH 8588 (1), all with the same collection
data as the holotype. FMNH 55284 (1), Panama,
Canal Zone, Mindi Cut. Paratypes of M. mindii:
FMNH 27218 (1), FMNH 27219 (1, CS), FMNH
27220 (1, CS), FMNH 27221 (1), FMNH 27222
(1, CS), FMNH 27223 (1, x), FMNH 27224 (1, x),
FMNH 27225 (1, x), FMNH 27226 (1, x), FMNH
27227 (1, x), FMNH 27228 (1, x), FMNH 27229
(1, x), FMNH 27230 (1, x), FMNH 27231 (1, x),
FMNH 27232 (1, x), FMNH 27233 (1, x), FMNH
27234 (1, x), FMNH 27235 (1, x), FMNH 27236
(1, x), FMNH 27237 (1, x), all same collection
data as holotype of M. mindii. FMNH 32171 (1,
x), FMNH 32172 (1, x), FMNH 32173 (1, x),
FMNH 32174 (1, x), FMNH 32175 (1, x),
Panama, Mindi Cut, Canal Zone. FMNH 37009
(1, x), FMNH 37010 (1), FMNH 37011 (1),
FMNH 37012 (1), FMNH 37013 (1), FMNH
37014 (1), FMNH 37015 (1), FMNH 37016 (1),
Panama, Pedro Miguel Locks. FMNH 37017 (1,
x), FMNH 37018 (1), FMNH 37019 (1), FMNH
37020 (1), Panama, Gatun Lake, Barro Colorado
Canal Zone. FMNH 84980 (1, x), Honduras,
small stream feeding into a tributary of the Rio
Patuca. GCRL 7850 (10), Panama, Colon, 1 km E
of Maria Chiquita at small bridge on Portobello
Road. GCRL 12147 (11), Panama, Colon, Devil’s
Beach, Fort Sherman, 09u229000N, 79u589030W
(from creek). GCRL 12674 (1), Panama, Canal
Zone, Gatun Locks, East Lane, upper chamber.
GCRL 12695 (13), Panama, Canal Zone, Gatun
Locks, East Lane, lower chamber. GCRL 12726
(41), Panama, Canal Zone, Gatun Locks, East
Lane, middle chambers. GCRL 12740 (1),
Panama, Colon, Devil’s Beach, Fort Sherman,
09u229000N, 79u589030W, 200 m upstream on E
side. UMMZ 180649 (1, x), Costa Rica, Limon,
Tortuguero Lagoon. UMMZ 180758 (5, x),
Panama, Barro Colorado Island, Gatun Lake.
UMMZ 197253 (1), Guatamala, Izabal, Rio
Paujila above El Golfete. UMMZ 199560 (2, x),
Honduras, Rio Patuca. UMMZ 199575 (4),
Honduras, Rio Patuca. UMMZ 199594 (1),
Honduras, Rio Patuca, Rapa Laguna. UMMZ
199611 (20, x), Honduras, Rio Sicre, Laguna
Sikalanka.
Leptophilypnus panamensis.—Paratypes of M. pana-
mensis: CAS 78978 (1), Panama, Rio Juan Diaz.
FMNH 27089 (1, CS), FMNH 27090 (1), FMNH
27091 (1, CS), FMNH 27092 (1, CS), FMNH
27093 (1, x), FMNH 27094 (1), FMNH 27095 (1),
FMNH 27096 (1), FMNH 27097 (1), FMNH
27098 (1), Panama, Rio Juan Diaz. FMNH 27099
(1, x), FMNH 27100 (1, x), FMNH 27101 (1, x),
FMNH 27102 (1, x), FMNH 27103 (1, x), FMNH
27104 (1, x), FMNH 27105 (1, x), FMNH 27106
(1, x), Panama, Rio Chorrera. FMNH 55285 (1),
Panama, Rio Juan Diaz. AMNH uncat. (20), Costa
Rica, Puntarenas, Rio Baru 1 km N of Dominical.
TU 25132 (109), Costa Rica, Puntarenas, Rio Baru
1 km N of Dominical. TU 84526 (6), Costa Rica,
Rio Grande de Terraba at Puerto Cortes.
Leptophilypnus guatemalensis.—UMMZ 144145
(40), Guatemala, upper Rio de la Pasion. UMMZ
144147 (102), Guatemala, upper Rio de la
Pasion. UMMZ 187938 (34), Guatemala, Alta
Verapaz, Arroyo Salaguna. UMMZ 187953 (52),
Guatemala, Alta Verapaz, Rio Semococh. UMMZ
188006 (5), Guatemala, Quiche, Arroyo Negro,
tributary of Rio Xacbal. UMMZ 187938 (34),
Guatemala, Alta Verapaz, Arroyo Salaguna.
UMMZ 190494 (22, x), Guatemala, Alta Verapaz,
Rio Candelaria de Yalicar. UMMZ 190770,
Guatemala, Alta Verapaz, tributary of Rio Canilla.
UMMZ 193916 (7), Guatemala, Alta Verapaz,
tributary to Rio Icbolay. UMMZ 194060 (10),
Guatemala, Alta Verapaz, Rio Chiyu. UMMZ
197087 (39, x), Guatemala, Huehuetenango,
Rio San Ramon. UMMZ 197094 (51), Guatemala,
Alta Verapaz, Rio Candelaria de Yalicar.
Microphilypnus amazonicus.—Holotype CAS 76819
(1), Brazil, Manaus, Igarape do Mai Joana. CAS
76108 (1), Brazil, Cucuhy (Sto. Antonio), Rio
Negro. CAS 76109 (1), Brazil, Colombian bord,
Cucuhy, Rio Negro. USNM 316898 (48, x),
Brazil, Amazonas, Janauaca, Lago do Castanho,
Sao Jose. USNM 316903 (18), Brazil, Amazonas,
near Manaus, Lago Janauari. USNM 316906 (30,
x), Brazil, Amazonas, Janauaca, Lago do Cas-
tanho, Sao Jose. USNM 316945 (33), Brazil,
Amazonas, Janauaca, Plantagao de Juta, Lago
Murumuru. USNM 316948 (30), Brazil, Amazo-
nas, Ilha de Marchantaria, Camaleao. USNM
316961 (30, x), Brazil, Amazonas, Janauaca,
Curral de Gado, Lago Murumuru.
Microphilypnus macrostoma.—Holotype CAS 76820
(1), Brazil, Manaus, Igarape do Mai Joana.
Microphilypnus ternetzi.—Syntypes CAS 76818 (2;
formerly IU 17702), Venezuela, Cano de Quir-
ibana near Caicara. CAS 118080 (2; formerly SU
18080), Venezuela, Rio Orinoco, Cano de Quir-
ibana. FMNH 110189 (1), FMNH 110190 (37, x),
Venezuela, Bolivar, Cano Mato.
THACKER ET AL.—SYSTEMATICS OF LEPTOPHILYPNUS 497

Microphilypnus sp.—ANSP 162696 (8), Venezuela,
Amazonas, Cano Caripo (1st R. Caiquiare cano
ca. 5 min. from confluence of Casiquiare and
Orinoco, left side). ANSP 162697 (1), Venezuela,
Amazonas, Cano of Rio Casiquiare ca. 22 km
downstream from mouth of Rio Pamoni (east
side). CAS 41734 (3), Colombia, ca. 20 mi. NW
of Leticia, Quebrada Tucuchira. FMNH 70136
(1), Brazil, Lago Timbo. FMNH 70137 (2, x),
Brazil, Lago Jurucui. FMNH 70138 (1), Brazil,
Igarape Agua Preta. FMNH 70139 (1), Brazil,
Lago do Caxias. FMNH 70140 (1), Brazil, Lago
Curi. FMNH 85517 (1), Venezuela, Amazonas,
San Fernando de Atabapo, Titi Lagoon. FMNH
85589 (3, x), Venezuela, Amazonas, Rio Pacia
Grande. UMMZ 204318 (6), UMMZ 204333 (4),
UMMZ 204355 (4), UMMZ 204531 (5), UMMZ
204392 (8, x), UMMZ 209803 (15, x), all Bolivia,
Beni, Rio Itenez. USNM 270004 (34), Venezuela,
Amazonas, Departamento Ature, Cano south of
El Burro. USNM 270006 (40+, x), Venezuela,
Amazonas, Departamento Rio Negro, Cano
Urami. USNM 326286 (23), Brazil, Amazonas,
Rio Urubu.
ACKNOWLEDGMENTS
Grateful acknowledgment is made to the staff
and institutions who provided specimens for
examination or on loan: M. Sabaj, D. Catania,
D. Nelson, M. Rogers, K. Swagel, S. LeCroy, H.
Bart, N. Rios, and J. Williams. We also thank D.
Rosen for collecting the specimens of Leptophi-
lypnus guatemalensis. Special thanks go to P.
Willink for providing specimens and photo-
graphing types. J. Seigel and R. Feeney expertly
radiographed many tiny specimens. M. Sabaj
provided the photo of Microphilypnus ternetzi and
information about its capture and ecology in
Venezuela, where he was assisted in the field by J.
Armbruster, M. Hardman, N. Lujan, L. de Souza,
and J. Arjoon. D. Geiger provided critique of the
manuscript and advice on matters of the ICZN, as
well as expert production of the photographic
figures. This study was supported by a grant from
the National Science Foundation (NSF DEB
0108416) and by grants from the W. M. Keck
and R. M. Parsons Foundations (to CET). We are
also grateful to M. Sabaj and three anonymous
reviewers for their helpful corrections and
suggestions.
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(CET) VERTEBRATES–ICHTHYOLOGY,NATURAL HIS-
TORY MUSEUM OF LOS ANGELES COUNTY,900
498 COPEIA, 2006, NO. 3

EXPOSITION BOULEVARD,LOS ANGELES,CALIFOR-
NIA 90007; (FP) COLLEGE OF SCIENCE AND
TECHNOLOGY,TEXAS A&M UNIVERSITY,CORPUS
CHRISTI,TEXAS 78412; AND (RS) TULANE UNIVER-
SITY MUSEUM OF NATURAL HISTORY,BELLE
CHASSE,LOUISIANA 70037. E-mail: (CET)
thacker@nhm.org; and (FP) frank.pezold@
tamucc.edu. Send reprint requests to CET.
Submitted: 13 Aug. 2005. Accepted: 2 May
2006. Section editor: D. Buth.
THACKER ET AL.—SYSTEMATICS OF LEPTOPHILYPNUS 499