Zootaxa 2616: 31–47 (2010)
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ISSN 1175-5326 (print edition)
Article
Copyright © 2010 · Magnolia Press
ZOOTAXA
ISSN 1175-5334 (online edition)
Three new species of Psilorhynchus from the Ayeyarwaddy River drainage,
Myanmar (Teleostei: Psilorhynchidae)
KEVIN W. CONWAY1* & RALF BRITZ2
1
Department of Wildlife and Fisheries Sciences and Texas Cooperative Wildlife Collection, Texas A&M University, College Station, TX
77843, USA. E-mail: [email protected]
2
Department of Zoology, Natural History Museum, Cromwell Road, London, SW7 5BD, UK. E-mail: [email protected]
Abstract
Psilorhynchus brachyrhynchus, new species, from the upper Ayeyarwaddy River drainage, northern Myanmar, is
distinguished based on a combination of characters, including a short snout (43–48% HL), scale-less ventral surface
between paired fins, and features of dorsal and caudal-fin pigmentation. Psilorhynchus piperatus, new species, from the
eastern slopes of the Rakhine Yoma mountain range, lower Ayeyarwaddy River drainage, Myanmar, is distinguished
based on its unique caudal-fin pigmentation. Psilorhynchus gokkyi, new species, also from the eastern slopes of the
Rakhine Yoma mountain range, lower Ayeyarwaddy River drainage, Myanmar, is distinguished based on unique shape
of its snout, which exhibits a deep notch at the level of the ethmoid region.
Key words: Taxonomy, Ostariophysi, Cypriniformes, Indo-Burma
Introduction
Species of the genus Psilorhynchus McClelland are small cypriniform fishes with arched backs and flattened,
frequently scale-less ventral surfaces. They inhabit fast flowing rivers and streams in the foothills of the
Himalayan, Indo-Burman, and Western Ghats mountain ranges (Rainboth 1983; Arunachalam &
Muralidharan 2008). In recent years several new species of Psilorhynchus have been described (Conway &
Kottelat 2007; Arunachalam et al. 2007; Nebeshwar et al. 2007; Arunachalam & Muralidharan 2008; Conway
& Mayden 2008a, b; Conway & Kottelat 2010), more than doubling the total number of species recognized
before 2007 to 15 (Eschmeyer et al. 1998).
Though several studies have investigated the phylogenetic position of Psilorhynchus (Chen 1981;
Šlechtová et al. 2007; Conway & Mayden 2007; He et al. 2008) the interrelationships amongst its species are
presently unknown (Conway & Kottelat 2007). Several of the species of Psilorhynchus described in recent
years, viz. P. amplicephalus Arunachalam, Muralidharan & Sivakumar, P. breviminor Conway & Mayden, P.
nepalensis Conway & Mayden, P. pavimentatus Conway & Kottelat, and P. rahmani Conway & Mayden are
similar to P. balitora (Hamilton) in scale and fin ray counts (29–34 lateral-line scales, 8 unbranched dorsal-fin
rays, 5–7 unbranched pectoral-fin rays, 8–10+7–9 principal caudal-fin rays) and general appearance (e.g. see
Conway & Mayden 2008b). The purpose of the present paper is to provide formal descriptions for three
additional new species of Psilorhynchus from the Ayeyarwaddy River drainage of Myanmar that are also
similar to P. balitora in meristic and morphometric characters and general appearance.
Materials and methods
Measurements and counts generally follow Conway & Kottelat (2007). Lateral-line scales are counted from
the anteriormost scale (the first scale to bear a canal) to the posteriormost scale of the caudal peduncle.
Accepted by R. Pethiyagoda: 3 Sep. 2010; published: 17 Sep. 2010
31
Lateral-line scale counts do not include those canal-bearing scales at the base of the caudal fin, which are
counted separately. The number of scale rows between the pectoral and pelvic fins includes those between the
posteriormost tip of the pectoral fin and the pelvic-fin origin when the pectoral fin is depressed against the
body. The number in parentheses following a meristic value denotes the frequency of that value. The last two
branched rays of the dorsal and anal fins that articulate with the same pterygiophore are counted separately.
Values for the recently described P. amplicephalus are taken from Arunachalam et al. (2007), as this species is
still known only from the type series, which was unavailable for study. Selected specimens were cleared and
doubled stained (c&s) for bone and cartilage study (Taylor & Van Dyke 1985). All fin-ray counts, excluding
those provided for P. amplicephalus, P. piperatus and P. gokkyi, were confirmed through the examination of
cleared and stained specimens. Vertebral counts are based on c&s specimens or radiographs and include the
four Weberian centra and the terminal compound centrum (Fink & Fink 1981). Collection abbreviations:
BMNH, Natural History Museum, London; NRM, Swedish Museum of Natural History, Stockholm.
Psilorhynchus brachyrhynchus new species
(Figure 1)
Psilorhynchus balitora (Mukerji 1933: plate I, 2–4).
Holotype. NRM 40935, male, 44.9 mm SL; Myanmar: Kachin State, Putao, Ayeyarwaddy River drainage, Ma
Kyaww Wa Chaung and its tributary Nan Hto Chaung, ca 1 mile from 46th regiment, close to rice mill, 27° 19'
44" N, 97° 22' 36" E, 28 March 1998, S. O. Kullander & R. Britz.
Paratypes. NRM 60761, 1, 42.6 mm SL; same data as holotype. NRM 40922, 15 (2c&s), 28.2–51.1 mm
SL; same locality as holotype, 27 March 1998, S. O. Kullander & R. Britz. NRM 59658, 1 (c&s), 40.9 mm
SL; same locality as holotype, 27 March 1998, S. O. Kullander & R. Britz. NRM 57222, 32.9 mm SL; same
locality as holotype, 27 March 1998, S. O. Kullander & R. Britz.
Other material examined. NRM 40630, 3, 40.0–45.7 mm SL; Myanmar: Kachin State, Putao, 27° 20'
60" N, 97° 23' 60" E, April 1934, Fan Li San.
Diagnosis. A species of Psilorhynchus most similar to P. amplicephalus, P. balitora, P. breviminor, P.
gokkyi, P. nepalensis, P. pavimentatus, P. piperatus and P. rahmani in general appearance. Psilorhynchus
brachyrhynchus is distinguished from P. amplicephalus, P. balitora, P. breviminor, P. gokkyi, P. nepalensis, P.
pavimentatus and P. piperatus by its shorter snout (snout length 43–48% HL vs. 48–56); from amplicephalus,
P. balitora, P. nepalensis, P. pavimentatus and P. piperatus by having more principal rays in the upper caudalfin lobe (10 vs. 8–9); from P. amplicephalus, P. balitora and P. nepalensis by the absence (vs. presence) of a
dark irregular vertical bar across the distal edge of the caudal fin; from P. balitora and P. nepalensis by the
absence (vs. presence) of a broad swath of melanophores across the anterior half of the dorsal fin; from P.
breviminor, P. gokkyi, P. pavimentatus, P. piperatus and P. rahmani by the presence (vs. absence) of a large
dark blotch at the base of each caudal fin lobe; and from P. breviminor, P. piperata and P. rahmani by the
presence (vs. absence) of an irregular vertical bar across the center of the caudal fin. Psilorhynchus
brachyrhynchus is further distinguished from the aforementioned species and all remaining congeners by the
following combination of characters: 2 branchiostegal rays; ventral surface between paired fins with
traingular scale-less patch; presence of a large postepiphysial fontanelle; branched dorsal-fin rays 9;
unbranched pectoral-fin rays 5; caudal-fin rays 10+9; lateral-line scales 32–34; lateral sides of body marked
with 5–7 indistinct round to squarish dark blotches, arranged in a longitudinal row; caudal fin with a dark,
irregular vertical bar across its center.
Description. General body shape as in Figure 1. Morphometric and meristic data are listed in Table 1.
Body deep, greatest depth at dorsal-fin origin. Dorsal profile arched, ventral profile straight from lower jaw to
anal-fin origin, with slight dorsad inclination from anal-fin origin to caudal-fin base.
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CONWAY & BRITZ
FIGURE 1. Psilorhynchus brachyrhynchus, NRM 40935, male, 44.9 mm SL; Myanmar: Kachin State, Putao.
Head small, eye large. Mouth inferior, snout short, rounded, its ventral surface bordered by a deep
longitudinal groove on each side. Rostral cap and upper lip fused, separated by a shallow groove. Lower jaw
covered by a thick squarish ‘cushion’ that can be folded backwards, the ‘cushion’ composed of two adnate
tissue layers: deeper layer (lower lip), smooth, not continuous with upper lip around corner of mouth;
superficial layer densely papilliated, thick, continuous with skin of isthmus, connected with rostral cap by
narrow strip of skin around corner of mouth, extended posteriorly, broadened as a ridged, heavily papillated
skin fold at posterolateral-most corner of mouth. Upper lip with numerous, horizontally arranged rows of
unculi. Pre-epiphysial fontanelle large, rectangular, extending from ethmoid region to epiphysial bar. Postepiphysial fontanelle large, irregularly shaped, extending from epiphysial bar to occipital region. Cranial
fontanelle separated by a narrow strut of frontal bone directly dorsal to the epiphysial bar. Five infraorbital
bones (IO1-5); IO1-3 platelike; IO4-5 reduced in width, composed of sensory-canal ossification only. Gill
membranes joined to isthmus. Fifth ceratobranchial with four needle-like pharyngeal teeth, arranged in a
single row. Branchiostegal rays 2; anteriormost branchiostegal articulating with medial face of anterior
THREE NEW PSILORHYNCHUS FROM MYANMAR
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ceratohyal absent. Anterior swimbladder chamber surrounded by a thick peritoneal tunic, partially enclosed in
a bony capsule formed anteriorly by lateral process of 2nd vertebral centrum, laterally by outer arm of os
suspensorium. Posterior swimbladder chamber greatly reduced in size.
TABLE 1. Selected morphometric and meristic data for Psilorhynchus brachyrhynchus holotype and 11 paratypes.
Standard length (mm)
Holotype
Range
Mean
St. Dev.
44.9
28.2–51.1
19.4
18.6–21.9
20.0
1.1
% of standard length
Body depth
Head length
20.9
19.6–23.2
21.0
1.0
Pre-dorsal length
48.5
47.7–53.6
50.0
1.5
Pre-pectoral length
19.6
17.0–20.9
19.1
1.2
Pre-pelvic length
48.7
48.2–52.4
49.8
1.3
Pre-anal length
79.9
78.2–82.4
79.6
1.8
Snout to anus length
57.2
57.2–60.0
58.7
1.1
Anus to anal fin length
21.6
18.5–22.3
20.3
1.1
Caudal-peduncle length
15.1
12.2–15.2
14.4
1.2
Caudal-peduncle depth
9.1
8.0–9.5
8.7
0.5
Caudal-peduncle width
5.3
4.2–5.4
4.8
0.4
Pectoral-fin length
27.2
24.5–27.3
25.9
0.9
20
17.8–20.8
19.9
0.8
Pelvic-fin length
Length of last unbranched anal-fin ray
15.7
15.0–18.2
16.3
1.0
Length of last unbranched dorsal-fin ray
23.4
18.9–23.8
22.6
1.4
Head width
70.2
64.3–70.2
67.3
2.6
Head depth
56.4
54.0–61.5
57.3
2.5
Eye diameter
25.5
22.5–28.7
26.4
1.8
Snout Length
44.7
43.1–48.4
45.9
1.6
Interorbital width
44.7
37.7–45.0
40.9
2.7
Mouth width
30.8
28.4–35.2
31.7
2.0
Dorsal-fin rays
iii.9
-
% of head length
Anal-fin rays
ii.6
-
Principal caudal fin-rays
10+9
-
Pectoral-fin rays
v.10
v.9–10
Pelvic-fin rays
ii.7
ii.6–7
Lateral-line scales
33
32–34
3.5/1/2
3.5/1/2–2.5
Circumpeduncular-scale rows
10
-
Preanal-scale rows
9
9–10
Predorsal-scale rows
11
10–12
Abdominal vertebrae
-
17–18
Caudal vertebrae
-
17–18
Total vertebrae
-
35
Scales between dorsal and pelvic fins
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Dorsal-fin rays iii.9, anal-fin rays ii.6. Principal caudal-fin rays 10+9, dorsal procurrent rays 7(2), ventral
procurrent rays 5(1) or 6(1). Pelvic-fin rays ii.6(4) or ii.7(13), pectoral-fin rays v.9(1), v.10 (11) or v.11(6).
Paired fins large, horizontally placed. Pectoral fin reaching vertical through dorsal-fin origin, reaching to one
or three scale rows anterior to pelvic-fin origin when adpressed. Pelvic-fin origin posterior to dorsal-fin
origin, insertion opposite 2nd branched dorsal-fin ray. Skin on ventral surface of unbranched pectoral- and
pelvic-fin rays thickened and covered in a layer of unculi, forming adhesive pads. Dorsal fin high, tip weakly
rounded, posterior margin straight to weakly concave. Anal fin short, tip pointed, posterior margin concave,
reaching to vertical through caudal-fin base when adpressed.
Anus positioned 2 scale rows posterior to insertion of pelvic fins. Scales large, 32(2), 33(10) or 34(5)
along lateral line, plus 1(2), 2(14) or 3(1) on base of caudal fin. 3.5/1/2(8) or 3.5/1/2.5(9) transverse scale
rows from dorsal-fin origin to pelvic-fin origin, 10 around caudal peduncle, 10(1), 11(13) or 12(2) predorsal
scales, 9(4) or 10(12) scales between anus and anal-fin origin. Ventral surface with a narrow, triangular scaleless patch between paired fins. Total number of vertebrae 35, comprising 17+18(3) or 18+17(1) abdominal
and caudal vertebrae.
Small conical tubercles with keratinised tips distributed over entire surface of snout, lateral surface of
head, rostral cap and papilliferous skin folds lateral to mouth. Head tuberculation more strongly developed in
males. Tubercles on dorsal surface of head arranged as a series of small, irregular longitudinal ridges. Scales
on anterior half of body with similar elongate tubercles, forming a series of small parallel ridges across scale
surface in both sexes, more strongly developed in males. Posterior edges of scales on dorsal and lateral body
surface of males each rimmed with four or five small conical tubercles with keratinized tip. Keratinized tips
most greatly developed on tubercles on anterior half of body. Strip of minute conical tubercles, multiple rows
thick, present along dorsal surface of unbranched and anteriormost branched pectoral-fin rays in males. Single
row of minute conical tubercles present along dorsal surface of unbranched and anteriormost branched
pectoral-fin rays in females. Single row of minute conical tubercles present along dorsal surface of
unbranched and anteriormost branched pelvic-fin rays and lateral surface of anteriormost dorsal-fin rays of
males only.
Coloration. In alcohol body background light cream (Fig. 1). Occiput dark brown. Dorsal surface
between occiput and dorsal fin with two faint brown saddles, first saddle situated closer to occiput than to
dorsal-fin origin, extending between predorsal scales 4–6, second saddle situated 1–3 scales anterior to dorsal
fin origin, extending to base of 1st branched dorsal-fin ray. Dorsal saddles between occiput and dorsal fin
most obvious in smaller specimens (below 40 mm SL), becoming increasingly less visible with size due to
occlusion by dark markings along posterior margins of predorsal scales. A small, prominent dark brown spot
situated at anteriormost point of dorsal fin. Four brown saddles along dorsal surface between mid-dorsal fin
and caudal-fin base. First saddle situated between insertions of branched dorsal-fins rays 3–9, second saddle
directly between dorsal-fin and anal-fin origin, third saddle directly above anterior half of anal fin, fourth
saddle situated anterior to caudal-fin base. Dorsal saddles between mid-dorsal fin and caudal-fin base
decreasing in size caudad, extending ventrad 2–3 scale rows on body side, connecting with round to squarish
dark-brown blotches arranged in a longitudinal row on flank.
Flank with 5–7 indistinct round to squarish dark-brown blotches, arranged in a longitudinal row. In
specimens with 5, first situated posterodorsal to opercle opening, extending beneath lateral-line scales 1–7 or
8, second extending beneath lateral-line scales 10–15, third extending beneath lateral-line scales 17–21, fourth
extending beneath lateral-line scales 24–28, fifth situated at base of caudal fin, extending beneath lateral-line
scales 30/31 to 32/33/34. Second and or third blotch described above often divided into two small separate
dark-brown blotches in specimens with blotch counts of 6 or 7. Scale row situated below lateral-line scale row
densely speckled with dark brown melanophores, forming an indistinct, irregular line between pectoral-fin
base and pelvic-fin origin, continued posteriorly as an indistinct, frequently interrupted streak, ventrad to
dark-brown round to squarish blotches. Scales at pelvic-fin origin darkly pigmented in a number of
specimens, forming an indistinct dark brown pre-pelvic spot. Large melanophores, deeply situated in
epidermis, forming short stripe between tip of snout and anterior edge of eye; a dark brown blotch-like
marking on cheek below ventral margin of eye; another at center of opercle.
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Ventral surface largely devoid of pigment except for melanophores on anterior edge of rostral cap; a small
patch of melanophores situated beneath scales at anal-fin origin; a short line of melanophores posterior to
anus, running along ventral midline beneath 3rd to 5th scale post anus in row between anus and anal-fin origin.
Broad swath of small melanophores at base of pectoral fin. Anteriormost pectoral- and pelvic-fin rays lightly
speckled with small dark melanophores. Pelvic fin with an indistinct stripe across its center, formed by small
aggregations of melanophores around first branching point of branched rays. Dorsal fin intensely marked with
a black proximal stripe running along base of rays; a more distal black stripe crossing center of fin, formed by
small aggregations of melanophores around first branching point of branched rays. Caudal fin with two large
black blotches, one at the base of each lobe; a single irregular black vertical bar across center of fin, formed by
small aggregations of melanophores around first branching point of branched rays. Anal fin immaculate.
Distribution. Known to date only from the upper Ayeyarwaddy River drainage, in the vicinity of Putao in
northern Myanmar (Fig. 2). The type locality, at the confluence of the Ma Kyaww Wa Chaung and its
tributary the Nan Hto Chaung (Fig. 3), is described in detail by Kullander & Britz (2002) and Kullander &
Fang (2005).
FIGURE 2. Distribution of Psilorhynchus brachyrhynchus (square), P. piperatus (star) and P. gokkyi (circle).
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FIGURE 3. Ma Kyaww Wa Chaung and its tributary Nan Hto Chaung, Putao, Kachin State, Myanmar. Type locality of
Psilorhynchus brachyrhynchus. Photograph by S. O. Kullander.
Etymology. Latinized from the Greek words brachys (βραχυς), short, and rhynchos (ρυγχος), snout, in
reference to the short snout of this species. An adjective.
Remarks. Psilorhynchus brachyrhynchus most closely resembles P. breviminor in general appearance
and in several meristics characters, including number of principal caudal fin rays (10+9), and unbranched
pectoral-fin rays (5). Psilorhynchus brachyrhynchus is easily distinguished from P. breviminor by features of
its caudal-fin pigment pattern (Fig. 4B), which consists of two large black blotches, one at the base of each
lobe, and a single irregular vertical black bar across the center of the fin, traversing both upper and lower
lobes. In P. breviminor the caudal fin lacks such distinctive blotches or vertical barring and instead exhibits
irregular black markings, which are most prominent along the outer edge of the upper and lower lobes (Fig.
4C). Several other species of Psilorhynchus, similar in general appearance to P. brachyrhynchus, also exhibit
black vertical barring on the caudal fin, including P. amplicephalus (see Arunachalum et al. 2007), P. balitora
and P. nepalensis (see Conway & Mayden 2008b). In each of these species, the proximalmost caudal bar is
dumbbell-shaped, being pinched at its center (Fig. 4A), and it is likely that the blotches at the base of the
caudal fin in P. brachyrhynchus are homologous with the proximalmost bar in P. amplicephalus, P. balitora
and P. nepalensis. Similarly, the vertical bar across the center of the caudal fin of P. brachyrhynchus is
considered to be homologous with the central caudal-fin bar of P. amplicephalus, P. balitora (Fig. 4A) and P.
nepalensis. Psilorhynchus brachyrhynchus lacks the distalmost caudal-fin bar present in P. amplicephalus, P.
balitora (Fig. 4A) and P. nepalensis. Other species of the genus lack vertical barring in the caudal fins (e.g. P.
arunachalensis (Nebeshwar, Bagra & Das), P. gokkyi [Fig. 4D], P. gracilis Rainboth, P. homaloptera Hora &
Mukerji, P. melissa [Fig. 4G], P. microphthalmus Vishwanath & Manojkumar, P. pavimentatus [Fig. 4E], P.
piperatus [Fig. 4F], P. pseudecheneis Menon & Datta, P. robustus Conway & Kottelat [Fig. 4H], P. sucatio
(Hamilton) and P. tenura Arunachalam & Muralidharan) or lack caudal-fin pigmentation entirely (P. rahmani;
Conway & Mayden 2008b). Psilorhynchus brachyrhynchus is further distinguished from similar-looking
species, including P. amplicephalus, P. balitora, P. breviminor, P. gokkyi, P. nepalensis, P. pavimentatus and P.
piperatus by its extremely short snout, which is only 43–48% HL (vs. 48–58% in P. amplicephalus, 50–53%
in P. balitora, 51–56% in P. breviminor, 51–57% in P. gokkyi, 48–55% in P. nepalensis, 50–55% in P.
pavimentatus, and 53–55% in P. piperatus).
Psilorhynchus brachyrhynchus is the only member of the genus (and the only member of the order
Cypriniformes; Conway et al. 2010) known to possess two branchiostegal rays (vs. three in all other species in
which this character has been examined). The two branchiostegal rays of P. brachyrhynchus each articulate
with the lateral face of the hyoid bar (the first at the suture between anterior and posterior ceratohyals and the
second with the posterior ceratohyal) and are considered homologous to the two posteriormost branchiostegal
THREE NEW PSILORHYNCHUS FROM MYANMAR
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rays of other cypriniform fishes. In a number of Psilorhynchus (viz., P. balitora, P. breviminor, P.
pavimentatus, P. rahmani and P. sucatio) the anteriomost branchiostegal ray, which articulates with the medial
face of the anterior ceratohyal, is composed of the articular head only and is much shorter than the two
posterior rays. In P. breviminor the anteriormost branchiostegal ray exhibits asymmetry, being present on the
left side only in two out of the three c&s specimens examined. Reduction of the anteriomost branchiostegal
ray is clearly a derived character and may be of utility in defining a monophyletic group within Psilorhynchus
(Conway & Kottelat 2010). The complete absence of this element in P. brachyrhynchus should also be
considered within this context.
FIGURE 4. Schematic illustration of caudal-fin pigmentation patterns in Myanmar species of Psilorhynchus and in P.
balitora. A. Psilorhynchus balitora, KU 29191, 45.5 mm SL. B. Psilorhynchus brachyrhynchus, NRM 40922, paratype,
45.5 mm SL. C. Psilorhynchus breviminor, ZRC 51222, holotype, 35.9 mm SL. D. Psilorhynchus gokkyi, BMNH
2010.4.14.1, holotype, 50.7 mm SL. E. Psilorhynchus pavimentatus, UMMZ 248831, holotype, 48.7 mm SL. F.
Psilorhynchus piperatus, BMNH 2010.4.14.8, holotype, 47.7 mm SL. G. Psilorhynchus melissa, UMMZ 248829,
holotype, 47.6 mm SL. H. Psilorhynchus robustus, ZRC 51111, holotype, 60.3 mm SL. Tips of caudal-fin membranes
frayed or torn in majority of specimens.
Mukerji (1933: plate I) illustrated a specimen of Psilorhynchus collected from a tributary stream of the
Mali Hka River, northern Myanmar (Myitkyina District) (Fig. 5). He referred this specimen to P. balitora, a
species restricted to the Ganges-Brahmaputra drainage of northern India (West Bengal and Assam), eastern
Nepal, and northern Bangladesh (Conway & Mayden 2008b). Based on features of the specimen figured by
Mukerji (1933), particularly the absence of scales from the midventral region and the presence of a distinctive
stripe across the center of the dorsal fin, Conway & Mayden (2008a) argued that this specimen did not belong
to P. balitora or P. breviminor, later suggesting (Conway & Mayden 2008b) that it likely represented an
undescribed species. We tentatively consider the specimen illustrated by Mukerji (1933) to belong to P.
brachyrhynchus, until more material becomes available.
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FIGURE 5. Psilorhynchus brachyrhynchus as illustrated in Mukerji (1933: plate I).
Psilorhynchus piperatus, new species
(Figure 6)
Holotype. BMNH 2010.4.14.8, 47.7 mm SL; Myanmar: Magwe Division, Man Chaung (Ayeyarwaddy River
drainage), 0.5 miles from Zinpyone village, 19° 55' 3" N, 94° 30' 11" E, 21 November 2009, R. Britz et al.
Paratype. BMNH 2010.4.14.9, 1, 42.6 mm SL; same data as holotype.
Diagnosis. A species of Psilorhynchus distinguished from all other species of the genus by its unique
caudal-fin pigmentation pattern, consisting of an approximately symmetrical pattern of small black blotches
on both upper and lower caudal-fin lobes (vs. caudal fin without pigmentation, with two to three irregular
vertical bars across center, or with an irregular pigmentation pattern, most prominent along outer edges of
upper and lower lobes). Psilorhynchus piperatus is further distinguished by the combination of the following
characters: snout length 53–55% HL; ventral surface between paired fins with a broad rectangular scale-less
patch; branched dorsal-fin rays 9; unbranched pectoral-fin rays 5; caudal-fin rays 9+9; lateral-line scales 32–
33; lateral sides of body marked with 6 indistinct round to squarish dark-brown blotches, arranged in a
longitudinal row; dorsal saddles deep, extending 3–4 scale rows downwards from the dorsal surface, in
contact with the round to squarish dark brown blotches, arranged in a longitudinal row on flank.
Description. General body shape as in Figure 6. Morphometric and meristic data are listed in Table 2. As
described for P. brachyrhynchus with the following differences. Snout long, contributing to 50% of head
length. Principal caudal-fin rays 9+9. Pelvic-fin rays ii.7, pectoral-fin rays v.11(1). Pectoral fin reaching to
one scale row anterior to pelvic-fin origin when adpressed. Scales large, 32(1) or 33(1) along lateral line, plus
2 on base of caudal fin. 13 predorsal scales, 9(1) or 10(1) scales between anus and anal-fin origin. Ventral
surface with a broad, rectangular scale-less patch between paired fins. Total number of vertebrae 35,
comprising 19+16 abdominal and caudal vertebrae.
Coloration. As described for P. brachyrhynchus, but with the following differences. Lateral body scales
irregularly pigmented, occluding round to squarish dark brown blotches, arranged in a longitudinal row on
flank. Dorsal fin weakly marked with a proximal stripe running along base of rays, a more distal stripe
crossing center of fin, formed by small aggregations of melanophores around first branching point of
branched rays. Caudal fin densely speckled with small dark clusters of melanophores, equally distributed
across both upper and lower lobes, forming an approximately symmetrical pattern (Fig. 4F).
Distribution and habitat. Psilorhynchus piperatus is known at present only from the type locality (Fig.
2). At the type locality, the Man Chaung is a swift-flowing river (Fig. 7), with dense riparian vegetation and a
substrate of sand, gravel and small boulders.
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Etymology. From the Latin piperatus, meaning peppered, in allusion to the speckling on the caudal fin.
An adjective.
Remarks. Psilorhynchus piperatus is easily distinguished from all other members of the genus by its
unique caudal-fin pigmentation pattern (Fig. 4F), which consists of a dense speckling of small black spots,
formed by clusters of melanophores, distributed evenly over both upper and lower caudal-fin lobes.
FIGURE 6. Psilorhynchus piperatus, BMNH 2010.4.14.8, holotype, 47.7 mm SL; Myanmar: Magwe Division, Man
Chaung.
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TABLE 2. Selected morphometric and meristic date for Psilorhynchus piperatus.
Holotype
Paratype
47.7
42.6
Body depth
21.2
21.8
Head length
22.4
25.4
Pre-dorsal length
51.9
52.3
Pre-pectoral length
19.9
21.8
Pre-pelvic length
50.7
50.4
Pre-anal length
79.9
78.1
Standard length (mm)
% of standard length
Snout to anus length
61.2
60.1
Anus to anal fin length
17.6
19.2
Caudal-peduncle length
11.3
13.4
Caudal-peduncle depth
9.4
9.1
Caudal-peduncle width
2.9
3.5
Pectoral-fin length
24.9
27.3
Pelvic-fin length
22.4
23.0
Length of last unbranched anal-fin ray
17.0
17.4
Length of last unbranched dorsal-fin ray
21.6
22.0
65.4
62.9
% of head length
Head width
Head depth
54.2
51.8
Eye diameter
28.0
25.9
Snout Length
55.1
52.7
Interorbital width
41.2
37.0
Mouth width
37.4
33.3
Dorsal-fin rays
iii.9
iii.9
Anal-fin rays
ii.6
ii.6
Principal caudal fin-rays
9+9
9+9
Pectoral-fin rays
v.11
v.11
Pelvic-fin rays
ii.7
ii.7
Lateral-line scales
33
32
Scales between dorsal and pelvic fins
1
1
Circumpeduncular-scale rows
10
10
Preanal-scale rows
9
10
Predorsal-scale rows
13
13
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FIGURE 7. Man Chaung, 0.5 miles from Zinpyone village, Magwe Division, Myanmar. Type locality of Psilorhynchus
piperatus.
Psilorhynchus gokkyi, new species
(Figures 8 & 9)
Holotype. BMNH 2010.4.14.1, male, 50.7 mm SL; Myanmar: Magwe Division, Pani Chaung (Ayeyarwaddy
River drainage), near Gokkyi village, 19° 49' 20" N, 94° 26' 8" E, 22 November 2009, R. Britz et al.
Paratypes. BMNH 2010.4.14.2-7, 6, 39.5–54.7 mm SL; same data as holotype. BMNH 2010.7.20.1-6, 6,
43.0–55.8 mm SL; same data as holotype.
Diagnosis. A species of Psilorhynchus distinguished from all other members of the genus by the presence
(vs. absence) of a deep notch situated at the level of the ethmoid region, visible as a square step-like division
between the snout and the head in lateral view and a deep groove in dorsal view. Psilorhynchus gokkyi is
further distinguished from members of this group by the following combination of characters: snout length
51–57% HL; ventral surface between paired fins with a broad triangular scale-less patch; branched dorsal-fin
rays 9–10; unbranched pectoral-fin rays 5–6; caudal-fin rays 10+9; lateral-line scales 32–34; lateral sides of
body marked with 6 indistinct round to squarish dark brown blotches, arranged in a longitudinal row; dorsal
saddles deep, extending 3–4 scale rows downwards from dorsal surface, in contact with the round to squarish
dark brown blotches, arranged in a longitudinal row on flank; caudal fin with an irregular pigmentation
pattern, most prominent along lower lobe.
Description. General body shape as in Figures 8–9. Morphometric and meristic data are listed in Table 3.
As described for P. brachyrhynchus, but with the following differences. Snout long, contributing to 51–57%
of head length. Ethmoid region with a deep notch, visible in dorsal view as a deep groove anterior to nostrils
and as a square step-like division between snout and head in lateral view. Dorsal-fin rays iii.9 (6) or iii.10 (1).
Pectoral-fin rays vi.10(4), v.11(2) or vi.11(2). Pectoral fin reaching two or three scale rows anterior to pelvicfin origin when depressed. Scales large, 32(4), 33(2) or 34(1) along lateral line, plus 2(4) or 3(3) on base of
caudal fin. 11(4), 12(2) or 13(1) predorsal scales, 8(1), 9(5) or 10(1) scales between anus and anal-fin origin.
Ventral surface with a broad triangular scale-less patch between paired fins. Total number of vertebrae 34,
consisting of 19+15(5) or 18+16(2) abdominal and caudal vertebrae.
Coloration. As described for P. brachyrhynchus with the following differences. Dorsal fin weakly
marked with a proximal stripe running along bases of rays, a more distal stripe crossing center of fin, formed
by small aggregations of melanophores around first branching point of branched rays. Caudal fin with a weak
irregular vertical black bar across center (Fig. 4D). Lower lobe of caudal fin additionally speckled with small
dense clusters of melanophores that gradually decrease in size posteriorly (Fig. 4D).
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FIGURE 8. Psilorhynchus gokkyi, BMNH 2010.4.14.1, holotype, male, 50.7 mm SL; Myanmar: Magwe Division, Pani
Chaung.
FIGURE 9. Psilorhynchus gokkyi, BMNH 2010.4.14.2-7, paratype. Myanmar: Magwe Division, Pani Chaung.
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In life (Fig. 9) background colour light creamy brown. Dorsal saddles, round-squarish blotches, arranged
in a longitudinal row on flank, head and snout markings, and markings on lower lobe of caudal fin dark
brown. Scales on lateral body sides with a silvery iridescent sheen. Paired and median fin markings, excluding
those on lower lobe of caudal fin, indistinct.
TABLE 3. Selected morphometric and meristic date for Psilorhynchus gokkyi holotype and six paratypes.
Holotype
Range
50.7
39.5–54.7
Mean
St. Dev.
Body depth
20.7
18.9–20.7
19.8
0.7
Head length
22.9
20.4–22.9
21.7
0.8
Pre-dorsal length
50.3
50.1–51.6
50.5
0.5
Pre-pectoral length
20.7
19.1–20.7
20.4
0.7
Pre-pelvic length
48.3
48.0–50.4
49.3
1.0
Pre-anal length
79.3
77.9–81.0
79.1
1.0
Standard length (mm)
% of standard length
Snout to anus length
57.6
57.6–60.1
59.0
1.1
Anus to anal fin length
23.1
19.7–23.1
21.0
1.0
Caudal-peduncle length
12.6
12.4–13.3
12.7
0.3
Caudal-peduncle depth
9.7
8.6–9.8
9.2
0.4
Caudal-peduncle width
3.4
2.8–4.0
3.2
0.4
Pectoral-fin length
24.5
23.4–27.3
25.0
1.2
Pelvic-fin length
20.3
20.1–22.8
21.3
1.0
Length of last unbranched anal-fin ray
18.5
15.9–18.5
17.2
0.9
Length of last unbranched dorsal-fin ray
22.9
21.8–23.6
22.7
0.6
64.7
64.0–71.6
66.6
2.6
% of head length
Head width
Head depth
52.6
50.9–56.1
53.8
1.7
Eye diameter
27.6
27.0–32.2
29.2
1.8
Snout Length
53.4
51.7–57.0
55.1
1.9
Interorbital width
38.8
37.5–45.2
40.4
3.4
Mouth width
28.4
28.4–34.5
30.9
2.0
Dorsal-fin rays
iii.9
iii.9–10
Anal-fin rays
ii.6
ii.5–6
Principal caudal fin-rays
10+9
-
Pectoral-fin rays
v.11
v–vi.10–11
Pelvic-fin rays
ii.7
-
Lateral-line scales
34
32–34
Scales between dorsal and pelvic fins
2
2–3
Circumpeduncular-scale rows
10
-
Preanal-scale rows
9
8–9
Predorsal-scale rows
11
11–13
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Distribution and habitat. Known to date only from the type locality (Fig. 2). At the type locality, Pani
Chaung is a swift-flowing stream with dense bank and overhanging vegetation, and a substrate of sand, gravel
and small boulders (Fig. 10).
FIGURE 10. Pani Chaung, near Gokkyi village, Magwe Division, Myanmar. Type locality of Psilorhynchus gokkyi.
Etymology. Named after Gokkyi, a small village above the type locality, to honour the hospitality and
help extended to the second author during his collection trip in November 2009. A noun in apposition.
Remarks. Psilorhynchus gokkyi is easily distinguished from all other members of the genus by the
presence (vs. absence) of its deep notch in the ethmoid region, visible in dorsal view as a deep groove just
anterior to the nostrils and as a square step-like division between the snout and the head in lateral view.
Amongst other members of Psilorhynchus, P. gokkyi is most similar in terms of general appearance to P.
amplicephalus, P. balitora, P. brachyrhynchus, P. breviminor, P. nepalensis, P. pavimentatus, P. piperatus and
P. rahmani. Psilorhynchus gokkyi is distinguished from P. amplicephalus, P. balitora, P. nepalensis, P.
pavimentatus and P. piperatus by having more caudal-fin rays (10+9 vs. 8–9+7–8 in P. balitora, 9+8 in P.
amplicephalus and P. nepalensis, and 9+9 in P. pavimentatus and P. piperatus). It is distinguished from P.
brachyrhynchus and P. rahmani by its longer snout (snout length 51–57% vs. 43–48% in P. brachyrhynchus
and 46–50 in P. rahmani), and from P. breviminor by it slightly longer caudal peduncle (caudal peduncle
length 12–13% vs. 10–12). It is further distinguished from P. balitora by possessing a broad, rectangular
scaleless patch on its ventral surface between the paired fins (vs. ventral surface between paired fins
completely scaled).
The type locality of P. gokkyi, Pani Chaung, is close to the type locality of Channa ornatipinnis, Waloun
Chaung. The latter is a tributary of Pani Chaung. Waloun Chaung was erroneously reported by Britz (2007) to
be in Rakhine State, but it is actually located in Magwe Division.
Discussion
Prior to 2007, only a single nominal species of Psilorhynchus (P. homaloptera rowleyi Hora & Misra) appears
to have been accurately reported from Myanmar (the report of P. balitora from Myanmar by Mukerji (1933) is
erroneous; see Conway & Mayden (2008a,b) and remarks section under the description of P. brachyrhynchus
above). In the last three years, however, a number of new species of Psilorhynchus have been described from
Myanmar, including P. robustus, Ataran River basin (Conway & Kottelat 2007), P. breviminor, Ayeyarwaddy
River drainage, central Myanmar (Conway & Mayden 2008a), and P. pavimentatus and P. melissa, Ann
Chaung drainage, Western slope of the Rakhine Yoma (Conway & Kottelat 2010). The descriptions of P.
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brachyrhynchus, P. gokkyi and P. piperatus thus brings the total number of species known to inhabit Myanmar
to eight, only four of which (P. brachyrhynchus, P. breviminor, P. gokkyi and P. piperatus) are inhabitants of
the Ayeyarwaddy, Myanmar’s largest river drainage.
The ichthyofauna of the western slope of the Rahkine Yoma contains a large number of endemic species,
including two species of Psilorhynchus (P. melissa and P. pavimentatus), and is frequently labeled as an area
of high endemism for freshwater fishes (Kullander & Fang 2004; Britz 2007 2010; Ng 2008; Kullander &
Fang 2009; Conway & Kottelat 2010). In contrast, species found on the eastern slopes of the Rakhine Yoma
may have a wider distribution within Myanmar, but important baseline distribution data are still lacking. For
example Badis ferrarisi, originally described from the Chin Hills (Kullander & Britz 2002) is also present
further south, on the eastern slope of the Rakhine Yoma (R. Britz, pers. obs.). It is thus unclear at present
whether P. gokkyi and P. piperatus are restricted to headwater streams along the eastern slope of the Rakhine
Yoma or exhibit a more widespread distribution throughout western Myanmar. Further collections from this
area, including the eastern slope of the Rakhine Yoma and Chin Hills, are clearly needed to provide a more
complete picture of the distribution of its freshwater ichthyofauna.
Comparative material. For a complete list of comparative material examined see Conway & Mayden
(2008a,b) with the addition of the following material: Psilorhynchus sucatio: NRM 52730, 2, 33.4–33.5 mm
SL; India: Assam, Kaloni, Rani Garden (Ranigodam; ornamental fish farm and tea garden), Kalmoni subdrainage, 26° 3' 42.01" N, 91° 37' 54.01 E, O. Åhlander et al., 26 October 2006. Psilorhynchus gracilis: NRM
46908, 3, 26.1–45.6 mm SL; India: Assam, Sessa River close to Patiola Village, about 30km SW of
Dibrugarh, 27° 18' 47.02" N, 94° 49' 45.98" E, 21 Jan 1998, F. Fang & A. Roos.
Acknowledgments
We are particularly grateful to Sven Kullander (NRM) for providing specimens, images and information about
the type locality of P. brachyrhynchus, to Te Yu Liao (NRM) for providing meristic counts on cleared and
stained specimens of P. brachyrhynchus, and to two anonymous reviewers for comments on an earlier version
of the manuscript. The second author thanks Oliver Crimmen, NHM, for his company and help in the field
and is deeply indebted to Salai Thein Maung of Gokkyi village, Myanmar, for his warm welcome and
outstanding help and support, which resulted in the discovery of one of the new species. We also thank U Khin
Ko Lay, Director General, Department of Fisheries, Yangon, Myanmar, for his support and for issuing the
necessary permits and U Tin Win, Hein Aquarium for various help. This research was funded by a National
Science Foundation’s Doctoral Dissertation Improvement grant (DEB-0808446 to KWC) and a collection
enhancement grant of the Zoology Department, Natural History Museum, London, to RB.
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