A new species of freshwater threadfin, Polynemus aquilonaris,
from Indochina, and redescription of Polynemus dubius Bleeker,
1853 (Perciformes: Polynemidae)
Hiroyuki Motomura
Fish Section, Division of Vertebrate Zoology, Australian Museum, 6 College Street, Sydney, New South Wales 2010, Australia(e-mail: motomurah@austmus.gov.au)
Received: March 29, 2002 / Revised: February 2, 2003 / Accepted: February 10, 2003

IchthyologicalResearch©The Ichthyological Society of Japan 2002

Ichthyol Res (2003) 50: 154–163
DOI 10.1007/s10228-002-0155-1

Abstract The taxonomic status of two nominal species of Polynemus, viz. P. dubius Bleeker, 1853 andP. longipectoralis Weber and de Beaufort, 1922, is revised. Although regarded as separate taxa up to thepresent time, examination of the holotype of P. longipectoralis revealed its close similarity to thetype series of P. dubius, in the synonymy of which the former is now included. Polynemus dubius isredescribed as a valid species and a lectotype of the species is designated. In addition, a new species, P.
aquilonaris, previously identified as P. dubius or P. longipectoralis, is described from Indochina on thebasis of 28 specimens. Polynemus aquilonaris differs from P. dubius in having higher counts of pored
lateral-line scales [80–86 (mode 81) vs. 69–79 (78) in the latter] and scale rows below the lateral line
[14–17 (mode 14, rarely 13 or 17) vs. 13 (rarely 12)], and lower counts of gill rakers [25–29 (mode 27)
vs. 29–33 (30), respectively]. The former is known from Indochina (Chao Phraya and Mekong Riversystems including Lake Tonle Sap), whereas the latter is currently known from the Malay Peninsula,
Sumatra, and Kalimantan.
Key words Polynemidae · Polynemus aquilonaris sp. nov. · Polynemus dubius · Polynemus
longipectoralisT

he freshwater threadfin, Polynemus dubius Bleeker,
1853, originally described from Sumatra andKalimantan, Indonesia, has long been regarded as a valid
species (e.g., Kottelat et al., 1993; Randall and Lim, 2000), a
second threadfin, P. longipectoralis Weber and de Beaufort,
1922, originally described from Kalimantan, Indonesia, also
having been regarded as a valid species by many researchers(e.g., Chevey, 1932; Kottelat, 1989; Talwar and Jhingran,1991; Mishra and Krishnan, 1993; Kottelat, 2001). Furthermore, Weber and de Beaufort (1922), Myers (1936), andRainboth (1996) all regarded both species as valid. Accordingly, their taxonomic status has been equivocal, contributing to the overall taxonomic confusion of Southeast
Asian Polynemus. Recently, Feltes (2002) recognized P.
longipectoralis as a junior synonym of the former, but gaveneither reasons nor an indication of materials examined.
Examination of the types of P. dubius and P.
longipectoralis, together with non-type specimens from Malaysia and Indonesia, has shown the two nominal species tobe conspecific, characterized by having seven pectoral
filaments, eight spines in the first dorsal fin, vomer withvilliform teeth, 69–79 pored lateral-line scales, and 29–33 gillrakers. Accordingly, P. longipectoralis is herein regarded as a
junior synonym of the former.
Polynemus dubius (⫽P. longipectoralis) has been considered to be widely distributed in Southeast Asia (e.g.,
Kottelat et al., 1993; Rainboth, 1996; Feltes, 2002). However,specimens collected from Indochina (Chao Phraya and

Mekong River systems), including Thailand, Cambodia,
Vietnam, and Laos, previously identified as P. dubius or
P. longipectoralis, are here considered to represent an
undescribed species of Polynemus, being distinguished fromP. dubius by numbers of pored lateral-line scales, scale rows
above the lateral line, and gill rakers.
This article includes a redescription of P. dubius (as asenior synonym of P. longipectoralis), with designation of a
lectotype, and a description of new species, P. aquilonaris,
with discussion of morphological variations. Detailed comparisons are made with other congeners.

Materials and Methods
Counts and measurements followed Motomura et al.
(2002a). Pectoral-fin ray counts included only those interconnected by a membrane, the lower free rays being considered separately; counts of pectoral filaments begin withthe anterior element. Standard length and total length are
expressed as SL and TL, respectively. Terminology of supraneural bones follows Mabee (1988), and the formula for
configuration of supraneural bones, anterior neural spines,
and anterior dorsal-fin pterygiophores follows Ahlstrom etal. (1976). Osteological characters were confirmed from Xray photos taken of all specimens. A lateral dissection (rightside) of the abdomen of all six non-type specimens of
Polynemus dubius and 12 specimens [ANSP 177982, 177984

New species and redescription of Polynemus(2 specimens); BSKU 14846–14848 (3); UMMZ 181266 (2),195407, 232331 (2); URM-P 13930] of P. aquilonaris confirmed the condition of a swimbladder. Institutional codes
follow Leviton et al. (1985), with an additional institutional
abbreviation as follows: Raffles Museum of Biodiversity
Research, Department of Biological Sciences, National University of Singapore (ZRC, formerly NMS).

Polynemus aquilonaris sp. nov.
(New English name: northern paradise fish)(Figs. 1–3; Tables 1, 3)
Holotype. URM-P 13930, 136 mm SL, Chao Phraya River(purchased at Samyan market by H. Senou), Thailand, 10 Feb. 1984.

155
Paratypes. 12 specimens, 64–145 mm SL. ANSP 177982, 108 mm SL,
Chao Phraya River in vicinity of Phayuha Khiri, Thailand; ANSP
177984 (2 specimens), 88–96 mm SL, eastern channel of Chao Phraya
River at Bang Pa-In, Ayutthaya, Thailand; CAS 92821, 114 mm SL,
Prachinburi, Thailand; NRM 24267, 104 mm SL, Mekong River below
Khone waterfalls, Laos; UMMZ 181145 (3), 132–139 mm SL, MekongRiver drainage at Toch, Banam (ca. 2 km above main stream of MekongRiver), Cambodia; UMMZ 195407, 105 mm SL, Koke Tong Canal,
tributary of Chao Phraya River, at 17.5 km north of Ayutthaya, Thailand; UMMZ 224815, 64 mm SL, Bassac River at An Phu, Vietnam;
UMMZ 232331 (2), 138–145 mm SL, Mekong River at Stung Treng,
Cambodia.
Other material. 15 specimens, 63–158 mm SL. BSKU 14846–14848(3 specimens), 96–108 mm SL, Lake Tonle Sap, Cambodia; NSMT-P
21772, 138 mm SL, Chao Phraya River at Nakhon Swan, Thailand;

Fig. 1. Photographs of Polynemus aquilonaris sp. nov. A URM-P 13930 (holotype), 136 mm SL, Thailand. B Underwater photograph (taken by Y.
Tohyama) in aquarium (specimen from Thailand, not retained)

156

Fig. 2. Geographic distribution of Polynemus aquilonaris sp. nov.
(circles) and P. dubius (triangles), based on specimens examined inthis study

NSMT-P 21775 (2), 83–105 mm SL, Lake Tonle Sap, Cambodia; NSMTP 21776, 133 mm SL, Chao Phraya River at Nakhon Swan, Thailand;
NSMT-P 47598 (2), 137–158 mm SL, Lake Tonle Sap, Cambodia;
UMMZ 181266 (2), 110–118 mm SL, Lake Tonle Sap at Kompong
Lvong, Cambodia; UMMZ 213356 (1 of 30 specimens), 63 mm SL,
Bassac River adjacent to Dong Phu, Phong Dinh, Vietnam; UMMZ
232689 (3), 118–133 mm SL, Tonle Sap River at second channel east of
Kompong Chhnang, Cambodia.

Diagnosis. A species of Polynemus with the following
combination of characters: 8 first dorsal-fin spines; 7 pectoral filaments, upper 2 filaments longer than TL; 3 anal-fin
spines; 80–86 (mode 81) pored lateral-line scales; 6–8 (7)scale rows above lateral line, 13–17 (14) below; 9–11 (10) gillrakers in upper series, 16–18 (17) in lower, 25–29 (27) total;
vomer with villiform teeth; orbit diameter 4% of SL; posterior portion of maxilla less than orbit diameter.
Description. Counts and proportional measurements aspercentages of SL of the holotype, paratypes, and non-typematerial of Polynemus aquilonaris are given in Table 1.
Characters given in the species’ diagnosis are not repeated
here. Data for the holotype are presented first, followed byother material data (if different) in parentheses.
Body oblong, compressed; occipital profile nearly straight
throughout life; upper jaw lip poorly developed (welldeveloped in larger specimens from Lake Tonle Sap,

H. Motomura

Cambodia); lower jaw lip well-developed, dentary teeth restricted to dorsal surface; maxilla covered with small scales;
posterior margin of preopercle serrated; posterior margin of
maxilla extending well beyond level of posterior marginof adipose eyelid; adipose eyelid poorly developed; teeth
villiform in broad bands on palatines and ectopterygoids;
ectopterygoids very small, length less than half that ofpalatines; vomerine teeth present (varying in number from
one to numerous, infrequently covered with thin skin); allfirst dorsal-fin spine bases of similar thickness; first spine offirst dorsal fin very small, third spine longest; first spine ofanal fin very small, third spine longest; all pectoral-fin rays
unbranched, inserted near midline of body; posterior tip of
pectoral fin just reaching to (same, just short of, or extending
slightly beyond) level of anal-fin origin; first pectoral filament shortest, not reaching to level of posterior tip of pelvic
fin; second pectoral filament just reaching to (same, notreaching to, or extending slightly beyond) level of posterior
tip of pelvic fin; third pectoral filament extending beyond(rarely just short of) level of posterior tip of pelvic fin;
fourth pectoral filament reaching to level of posterior baseof anal fin (same, extending beyond level of anal-fin origin,or reaching to level of middle of anal-fin base); fifth pectoral
filament extending beyond level of posterior tips of caudalfin lobes (same or level of mid-distal margin of caudal-fin
membrane); sixth (usually longest) and seventh pectoral
filaments longer than other filaments, extending well beyond posterior tips of caudal-fin lobes; lateral line simple,
extending from upper end of gill opening to mid-distal
margin of caudal-fin membrane; formula for configurationof supraneural bones, anterior neural spines, and anterior
dorsal pterygiophores /0/0 ⫹ 2/1/1 ⫹ 1/1/1/1/ (same or /0/0
⫹ 2/1 ⫹ 1/1/1/1/1/); 5 (same or 6, rarely 4) epineurals;
10 ⫹ 15 vertebrae; swimbladder not apparent (same orpresent, varying in size less than ca. 23% of SL).
Life color.—Based on color transparencies of a live specimen that was not retained (Fig. 1B) and ANSP 177984(88 mm SL, Thailand): head and body grayish-silver dorsally,
silver ventrally; anterior margin of first dorsal fin and posterior margin of second dorsal fin blackish, remaining partstranslucent; pectoral fin translucent; base of pectoral filaments white, becoming blackish on posterior tips; base andposterior margin of pelvic fin white, remaining parts translucent; posterior margin of anal fin translucent, remaining
parts white; posterior margin of caudal fin translucent, remaining parts white.
Color of preserved specimens.—Head and body gray dorsally, pale silver ventrally; posterior tip of first dorsal fin
blackish, remaining parts yellowish-silver; posterior margins
of second dorsal, anal, and caudal fins translucent, remaining parts pale yellow; pectoral fin and filaments translucent,rarely with a small number of scattered melanophores;
pelvic fin pale yellow.
Geographical distribution and habitat. Polynemus
aquilonaris occurs on sandy or muddy bottoms in freshwater rivers and estuaries, being currently known from the
Chao Phraya River system (Thailand), Mekong River system below the Khone waterfalls of Laos (Cambodia, southernmost of Laos, and southern Vietnam), and Lake

New species and redescription of Polynemus

157

Table 1. Counts and measurements of Polynemus aquilonaris sp. nov., including the holotype, paratypes, and non-type specimens, expressed aspercentages of standard length

Standard length (mm)Counts
Dorsal-fin rays
Anal-fin rays
Pectoral-fin rays
Pectoral filaments
Pelvic-fin rays
Pored lateral-line scales
Scales above/below lateral line
Gill rakers
Measurements (means)
Head length
Body depth at 1st dorsal-fin origin
Body depth at 2nd dorsal-fin origin
Body width at pectoral-fin base
Snout length
Dermal eye opening
Orbit diameter
Interorbital width
Postorbital length
Upper jaw length
Depth at posterior margin of premaxilla
Pre-1st dorsal-fin lengthPre-2nd dorsal-fin length
Preanal-fin length
Pelvic-fin origin to anal-fin origin
Second dorsal-fin base length
Anal-fin base length
Longest pectoral-fin length
Longest pectoral-filament length
Pectoral-fin base including filament baseLongest pelvic-fin ray length
Longest 1st dorsal-fin spine length
Second dorsal-fin spine length
Longest 2nd dorsal-fin ray length
Longest anal-fin spine length
Longest anal-fin ray length
Caudal-peduncle length
Caudal-peduncle depth
Upper caudal-fin lobe length
Lower caudal-fin lobe length

Holotype of
Polynemus aquilonaris
URM-P 13930

Paratypes of
Polynemus aquilonaris(n ⫽ 12)

Non-type specimens of
Polynemus aquilonaris(n ⫽ 15)136

64–14563–158

VIII-I, 17
III, 12
17
7
I, 5
84
7/14
11 ⫹ 18 ⫽ 29

VIII-I, 15–19
III, 12–13
15–17
7
I, 5
80–86
6–8/13–16
9–11 ⫹ 16–18 ⫽ 25–29

VIII-I, 16–18
III, 11–12
16–17
7
I, 5
80–85
6–8/14–17
10–11 ⫹ 16–18 ⫽ 26–28

26
24
26
14
6
3
4
7
18
11
3
32
59
60
29
21
16
35
309
13
16
21
7
21
8
20
27
12
44
38

25–29
22–26
24–28
13–16
5–7
3–4
4
7–9
16–19
10–12
2–3
32–36
57–60
56–61
26–30
19–23
15–17
34–40
260–371
13–15
18–20
20–21
6–8
20–23
8–11
18–22
25–28
10–12
39–44
33–41

24–26 (26)
23–26 (25)
24–28 (26)
13–16 (14)
5–6 (5)
3–4 (3)4 (4)
6–8 (8)
16–18 (17)
10–11 (11)
2–3 (3)
32–34 (34)
58–61 (59)
57–62 (60)
26–33 (29)
18–23 (21)
14–17 (16)
34–41 (37)266–314 (308)
13–15 (14)18–20 (18)
20–21 (21)
6–8 (7)
20–23 (22)
8–11 (9)18–22 (21)25–28 (27)
10–12 (11)39–44 (43)
33–41 (38)Means in parentheses include data of type specimens

Tonle Sap and related rivers (Cambodia) (see Fig. 2). Two
specimens (NSMT-P 21772–21776, 133–138 mm SL),
collected from the Chao Phraya River at Nakhon Sawan,
Thailand, represent the northernmost reliable record of thespecies.
Etymology. The specific name “aquilonaris” is derived
from the Latin meaning “northern,” in reference to thenorthern distribution (Indochina) of the species, comparedwith that of a related species, Polynemus dubius (distributedin Malaysia and Indonesia).

Remarks. Polynemus aquilonaris, previously identified
as P. dubius (e.g., Suvatti, 1981; Rainboth, 1996) or P.
longipectoralis (e.g., Rainboth, 1996; Kottelat, 2001), is
herein regarded as representing a new species on the basisof its unique combination of morphological characteristics(see Comparisons).
Polynemus aquilonaris is currently known from
Indochina (Chao Phraya and Mekong River systems),
whereas P. dubius is distributed in rivers on the Malay Peninsula, Sumatra, and Kalimantan (Fig. 2). The distributions

158

H. Motomura
Sampit, Kalimantan, and Palembang, Sumatra, Indonesia, based on
P. longifilis of Bleeker (1851, 1852)].
Polynemus longipectoralis Weber and de Beaufort, 1922: 213 (typelocality: Banjarmasin, Kalimantan, Indonesia).

Fig. 3. Head of Polynemus aquilonaris sp. nov. A NSMT-P 47598,
158 mm SL, Lake Tonle Sap, Cambodia. B UMMZ 232331, 138 mm SL,
Mekong River, Cambodia

of both species are most likely to be relictual, being presently consistent with the location of Sundaland (see Morleyand Flenley, 1987: fig. 5.5) during the last Pleistocene glacial
period. According to Bornbusch and Lundberg (1989),
Sundaland was drained by several major river systems,
at least two of which may have participated in faunal
mixing. These systems included the South Indo-China
River and North Sunda River, which are now restricted
to drainages on Indochina, and Malay Peninsula, Sumatra,
and Kalimantan, respectively, following submergence of
Sundaland owing to increased sea levels (ca. 150 m). The
present distributional ranges of P. aquilonaris and P. dubius
indicate that they evidently originated in the South IndoChina and North Sunda Rivers, respectively.
Morphological variations. Larger specimens (NSMT-P
47598, 2 specimens, 137–158 mm SL; UMMZ 181266, 2, 110–118 mm SL) of Polynemus aquilonaris collected from Lake
Tonle Sap had a fleshy lip on the upper jaw (Fig. 3A),
smaller specimens (BSKU 14846–14848, 3 specimens, 96–
108 mm SL; NSMT-P 21775, 2, 83–105 mm SL) from the lake
and all those from other localities having a relatively thin lip(Fig. 3B).
Apart from the lip condition in larger specimens of P.
aquilonaris, the two geographical forms were difficult todistinguish between because their meristic characters andproportional measurements fully overlapped. Although thedifference between the two forms is small, I excluded specimens collected from Lake Tonle Sap and adjacent watersfrom the type series of P. aquilonaris under Article 72.4.1(ICZN, 1999) (listed as other material). More studies of thetwo forms of P. aquilonaris are needed to assess whether
the two represent separate subspecies like P. melanochirmelanochir and P. m. dulcis (see Motomura and Sabaj, 2002).

Polynemus dubius Bleeker, 1853
(English name: eastern paradise fish)(Figs. 2, 4; Tables 2, 3)
Polynemus longifilis (not of Cuvier): Bleeker, 1851: 268 (Banjarmasin,
Kalimantan, Indonesia); Bleeker, 1852: 418 (Banjarmasin andSampit, Kalimantan, and Palembang, Sumatra, Indonesia).
Polynemus dubius Bleeker, 1853: 92 [type locality: Banjarmasin andLectotype. RMNH 6014, 126 mm SL, Banjarmasin, Sampit or
Palembang, Indonesia.
Paralectotypes. RMNH 34452 (7 specimens; formerly RMNH
6014), 77–132 mm SL, same data as lectotype.
Other material. 7 specimens, 81–184 mm SL. BMNH 1880.4.21.145,
129 mm SL, locality unknown; FMNH 81557, 110 mm SL, mouth ofMuar River, Muar, Malaysia; FMNH 81602, 81 mm SL, mouth of Muar
River, Muar, Malaysia; RMNH 34453 (formerly RMNH 6014), 150 mm
SL, data unknown; WAM-P 30529-003, 140 mm SL, Kuala Kangsar,
Malaysia; ZMA 112.570 (holotype of Polynemus longipectoralis Weberand de Beaufort), 133 mm SL, Banjarmasin, Kalimantan, Indonesia;
ZRC 39004, 184 mm SL, Jambi (⫽Telanai Pura), Sumatra, Indonesia.

Diagnosis. A species of Polynemus with the following
combination of characters: 8 first dorsal-fin spines; 7 pectoral filaments, upper 2 filaments longer than TL; 3 anal-fin
spines; 69–79 (mode 78) pored lateral-line scales; 6–8 (7)scale rows above lateral line, 12 or 13 (13) below; 11–13 (12)gill rakers in upper series, 18–21 (18) in lower, 29–33 (30)
total; vomer with villiform teeth; orbit diameter 3–4%
(mean 4%) of SL; posterior portion of maxilla less thanorbit diameter.
Description. Counts and proportional measurements aspercentages of SL of the lectotype, paralectotypes, andother material of Polynemus dubius, including the holotypeof P. longipectoralis, are given in Table 2. Characters given in
the species’ diagnosis are not repeated here. Data for the
lectotype are presented first, followed by other material
data (if different) in parentheses.
Body oblong, compressed; occipital profile nearly straight
throughout life; upper jaw lip poorly developed; lower jaw
lip well-developed, dentary teeth restricted to dorsal surface; maxilla covered with small scales; posterior margin of
preopercle serrated; posterior margin of maxilla extending
well beyond level of posterior margin of adipose eyelid;
adipose eyelid poorly developed; teeth villiform in broad
bands on palatines and ectopterygoids; ectopterygoids verysmall, length less than half that of palatines; all first dorsalfin spine bases of similar thickness; first spine of first dorsal
fin very small, third spine longest; first spine of anal fin verysmall, third spine longest; all pectoral-fin rays unbranched,inserted near midline of body; posterior tip of pectoral finjust reaching to (same, just short of, or extending slightly
beyond) level of anal-fin origin; first pectoral filament shortest, not reaching to level of posterior tip of pelvic fin; second
pectoral filament extending slightly beyond (same or notreaching to) level of posterior tip of pelvic fin; third pectoral
filament extending beyond (rarely just short of) level ofposterior tip of pelvic fin; fourth pectoral filament reaching
to level of middle of anal-fin base (same, extending beyond
level of anal-fin origin or level of posterior base of anal fin);(fifth pectoral filament extending beyond level of posterior
tips of caudal-fin lobes); (sixth, usually longest, and seventh
pectoral filaments longer than other filaments, extending
well beyond posterior tips of caudal-fin lobes); lateral lineNew species and redescription of Polynemus

159

Fig. 4. Photographs of Polynemus dubius. A RMNH 6014 (lectotype of P. dubius), 126 mm SL, Kalimantan or Sumatra, Indonesia. B ZMA 112.570(holotype of P. longipectoralis), 133 mm SL, Kalimantan, Indonesia. C ZRC 39004 (non-type specimen of P. dubius), 184 mm SL, Sumatra,Indonesia

simple, extending from upper end of gill opening to
mid-distal margin of caudal-fin membrane; formula for
configuration of supraneural bones, anterior neural spines,
and anterior dorsal pterygiophores /0/0 ⫹ 2/1/1 ⫹ 1/1/1/1/(same or /0/0 ⫹ 2/1 ⫹ 1/1/1/1/1/); 6 (same or 5) epineurals;
10 ⫹ 15 vertebrae; swimbladder not apparent.
Color of preserved specimens.—Head and body gray dorsally, pale silver ventrally; anterior margin and posterior tip
of first dorsal fin blackish, remaining parts yellowish-silver;
posterior margins of second dorsal, anal, and caudal finstranslucent, remaining parts pale yellow; pectoral fin andfilaments translucent or white without melanophores; pelvic
fin pale yellow.
Geographical distribution and habitat. Polynemus
dubius occurs on sandy or muddy bottoms in freshwater

rivers and estuaries, being currently known from theKangsar and Muar Rivers (western Malaysia in Malay Peninsula), Musi and Batanghari Rivers (southeastern Sumatra,Indonesia), and Sampit and Barito Rivers (southern
Kalimantan, Indonesia) (see Fig. 2).
Designation of a lectotype. Polynemus dubius Bleeker,
1853 was based on Bleeker’s (1851, 1852) descriptions of a
species originally believed by him to represent P. longifilis(true P. longifilis Cuvier in Cuvier and Valenciennes, 1829
has recently been regarded as a junior synonym of P.
paradiseus; see Motomura et al., 2002b), eight specimens,
90–190 mm TL, having been used by Bleeker for those initialdescriptions. Subsequently, Hubrecht (1879) referred to a
total of 11 Bleeker specimens as Trichidion dubium (groupA, 8 specimens; group B, 1 specimen; group C, 1 specimen;

160

H. Motomura

Table 2. Counts and measurements of Polynemus dubius, including the lectotype, other types, and non-type specimens, expressed as percentagesof standard length

Standard length (mm)Counts
Dorsal-fin rays
Anal-fin rays
Pectoral-fin rays
Pectoral filaments
Pelvic-fin rays
Pored lateral-line scales
Scales above/below lateral line
Gill rakers
Measurements (means)
Head length
Body depth at 1st dorsal-fin origin
Body depth at 2nd dorsal-fin origin
Body width at pectoral-fin base
Snout length
Dermal eye opening
Orbit diameter
Interorbital width
Postorbital length
Upper jaw length
Depth at posterior margin of premaxilla
Pre-1st dorsal-fin lengthPre-2nd dorsal-fin length
Preanal-fin length
Pelvic-fin origin to anal-fin origin
Second dorsal-fin base length
Anal-fin base length
Longest pectoral-fin length
Longest pectoral-filament length
Pectoral-fin base including filament baseLongest pelvic-fin ray length
Longest 1st dorsal-fin spine length
Second dorsal-fin spine length
Longest 2nd dorsal-fin ray length
Longest anal-fin spine length
Longest anal-fin ray length
Caudal-peduncle length
Caudal-peduncle depth
Upper caudal-fin lobe length
Lower caudal-fin lobe length

Lectotype of
Polynemus dubius
RMNH 6014

Paralectotypes of
Polynemus dubius
RMNH 34452 (n ⫽ 7)

Holotype of
Non-type specimens of
Polynemus longipectoralis Polynemus dubius
ZMA 112.570(n ⫽ 6)126

77–132133

81–184

VIII-I, 16
III, 12
17
7
I, 5
78
7/14
12 ⫹ 18 ⫽ 30

VIII-I, 15–16
III, 12
16–18
7
I, 5
75–81
6–8/13–14
11–13 ⫹ 18–21 ⫽ 29–33

VIII-I, 15
III, 12
17
7
I, 5
79
6/13
11 ⫹ 18 ⫽ 29

VIII-I, 14–16
III, 12
16–18
7
I, 5
69–79
6–8/12–14
11–13 ⫹ 19–21 ⫽ 30–33

26
24
25
12
6
3
3
7
17
12
3
34
58
59
26
20
15
40
Broken
14
16
22
8
20
9
20
27
11
46
36

24–27
20–24
24–26
11–13
5–6
3
3–4
7–8
16–18
10–12
2–4
33–34
57–59
56–60
27–31
19–21
14–16
30–39
Broken
13–14
14–18
18–21
5–9
20–21
7–10
17–21
26–29
10–11
37–47
33–41

24
23
25
13
5
3
4
7
16
10
3
34
58
61
30
19
14
35
Broken
14
17
18
6
20
9
18
27
11
39
35

25–27 (26)
23–28 (24)
24–28 (25)
11–15 (13)
5–6 (6)
2–3 (3)
3–4 (4)
7–8 (8)
17–18 (17)
11–13 (11)
3–4 (3)33–36 (34)
58–61 (58)
58–60 (59)25–30 (28)
19–22 (20)
15–16 (15)34–39 (37)264–312 (293)
14–15 (14)
16–20 (17)18–20 (19)
6–8 (7)
20–23 (21)
8–11 (9)19–22 (19)28 (28)
11–13 (11)35–50 (42)34–47 (39)

Means in parentheses include data of type specimens

group D, 1 specimen). Although the eight specimens ofgroup A are most likely to be the true syntypes of P. dubius,
all 11 specimens have been mixed at some time in the pastand registered together, as RMNH 6014: [61mm SL (caudal
fin broken), 77 mm SL (110 mm TL), 79 mm SL (108 mm TL),
83 mm SL (113 mm TL), 106 mm SL (ca. 148–159 mm TL,
caudal fin broken), 107 mm SL (152 mm TL), 110 mm SL (ca.
154–165 mm TL, caudal fin broken), 114 mm SL (165 mm
TL), 126 mm SL (181mm TL), 132mm SL (188 mm TL), and
150 mm SL (202 mm TL)]. Although the caudal fin was dam-

aged in three specimens (61, 106, and 110 mm SL), the original total lengths of these individuals (except for the first,
which represented a different species from P. dubius; seebelow) were estimated from the measurements of 13 undamaged P. dubius (77–184 mm SL) examined during thisstudy (total length 1.4–1.5 times SL).
With the exception of two specimens (61 and 107 mm SL),
all those in RMNH 6014 had the vomer with villiform
teeth, being one of the diagnostic characters of P. dubius.
The remaining two specimens, lacking vomerine teeth,

New species and redescription of Polynemus

161

Table 3. Frequency distribution of selected meristic characters of Polynemus aquilonaris sp. nov. and P. dubius
Second dorsal-fin soft rays

P. aquilonaris
P. dubiusn ⫽ 28n ⫽ 15Anal-fin soft rays

Pectoral-fin rays

14

15

16

17

18

19

11

12

13

15

16

17

18

—
1

1
3

15
11b

9a
—

2
—

1
—

3
—

24a
15b

1
—

1
—

17
7

10a
6b

—
2

Pored lateral-line scales

P. aquilonaris
P. dubiusn ⫽ 24n ⫽ 12

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

—
1

—
—

—
—

—
1

—
1

—
1

—
2

—
1

—
1b

—
3

—
1

5
—

8
—

3
—

3
—

2a
—

2
—

1
—

Scales above/below lateral line

P. aquilonaris
P. dubiusn ⫽ 22n ⫽ 12

6

7

8

8
5

12a
6b

2
1

Upper gill rakers

P. aquilonaris
P. dubiusabn ⫽ 28n ⫽ 15

/

12

13

14

15

16

17

—
2

1
10b

12a
—

6
—

2
—

1
—

Lower gill rakers

Total gill rakers

9

10

11

12

13

16

17

18

19

20

21

25

26

27

28

29

30

31

32

33

2
—

15
—

11a
4

—
9b

—
2

7
—

13
—

8a
7b

—
6

—
—

—
2

2
—

4
—

10
—

6
—

6a
3

—
5b

—
3

—
2

—
2

Holotype of P. aquilonaris
Lectotype of P. dubius

are herein considered to represent a different species fromP. dubius. In fact, they were also characterized by sevenpectoral filaments and eight spines in the first dorsal fin,characters consistent with the diagnosis of P. melanochirmelanochir given by Motomura and Sabaj (2002). Because
Bleeker (1853) had recognized the differences between
P. dubius and Bleeker’s P. macronema (not of Pel’s P.
macronema; later replaced with P. borneensis Bleeker),which has been regarded as a junior synonym of P. m.
melanochir (see Motomura and Sabaj, 2002), the two specimens are most likely to be included in RMNH 6014 after theoriginal description of P. dubius. Accordingly, the two specimens identified as P. m. melanochir (not P. dubius) are excluded from the syntypical series of P. dubius (reregisteredas RMNH 34454).
Of the remaining nine specimens in RMNH 6014, thelargest (150mm SL) was not included in the syntypical series because its total length (202mm) was outside the length
range (90–190 mm TL) given by Bleeker (1851, 1852). That
specimen has therefore been reregistered as RMNH 34453(as a non-type Bleeker specimen). Accordingly, the remaining eight specimens (77, 79, 83, 106, 110, 114, 126, and
132 mm SL) are herein regarded as the original syntypes ofP. dubius.
The proposal of a lectotype for P. dubius is justified,owing to the similarity of that species to other congeners.
Although Bleeker’s (1983) figures were usually reproduced
as life size (Motomura et al., 2001), that (1983: Polynemat.
pl. 5, pl. 457, fig. 1) of P. dubius (as Trichidion dubium)

measured ca. 210 mm TL, outside the length range of the
syntypes. Therefore, the figure may have been enlarged
or was based on a non-type specimen. Although ICZN
(1999: Article 74.7, Recommendation 74B) has recommended that an illustrated specimen should be designatedas lectotype in the first instance, the identity of the specimen
used here is unknown. Accordingly, I selected the specimen
in the best condition (126 mm SL; Fig. 4A) from the eight
syntypes and herein designate it as the lectotype of P.
dubius, the remaining syntypes becoming paralectotypes[reregistered as RMNH 34452 (77, 79, 83, 106, 110, 114, and
132 mm SL)].
Synonymy. Although Polynemus dubius has been regarded as a valid species (e.g., Kottelat et al., 1993; Randalland Lim, 2000), P. longipectoralis has also been regarded asa valid species by many researchers (e.g., Chevey, 1932;
Kottelat, 1989, 2001; Talwar and Jhingran, 1991; Mishra andKrishnan, 1993), but without comparisons of each nominal
species. Weber and de Beaufort (1922), Myers (1936), andRainboth (1996) regarded both species as valid, the firstmentioned believing P. dubius and their new species, P.
longipectoralis, to be distinguished by the number of lateralline scales [stated as 67 in P. dubius (based on a single
specimen) vs. 84 in P. longipectoralis (based on the holotype), but in fact 79, according to examination of that specimen during this study; see Table 2].
The diagnostic characters (seven pectoral filaments, eightspines in the first dorsal fin, 79 pored lateral-line scales, 13
scale rows below lateral line, vomer with villiform teeth, and162

posterior portion of the maxilla less than orbit diameter)
found in the holotype of P. longipectoralis are consistent
with those of specimens (including the newly designatedlectotype) of P. dubius. Accordingly, P. longipectoralis isherein regarded as a junior synonym of the latter.
Incidentally, Rainboth (1996) also distinguished between
the two nominal species by the number of lateral-line scales(65–67 in P. dubius vs. 80–85 in P. longipectoralis). However,
his P. longipectoralis is in fact P. aquilonaris. Myers (1936)
distinguished the two nominal species by the numberof first dorsal-fin spines (7 in P. dubius vs. 8 in P.
longipectoralis). However, P. dubius, including the holotypeof P. longipectoralis, in fact has eight spines in the first dorsal
fin. Polynemus hornadayi Myers, 1936 and P. paradiseus
are the only polynemid species with seven spines in thefirst dorsal fin (Motomura et al., 2002b). The first spine of
the first dorsal fin of Myers’ (1936) P. dubius was apparently
overlooked by him because of its very small size, and his
P. dubius has probably included P. aquilonaris and P.
dubius.
Comparisons. The genus Polynemus consists of seventaxa (Motomura and Sabaj, 2002; Motomura et al., 2002b;
this study): P. aquilonaris, P. dubius, P. hornadayi, P.
melanochir dulcis, P. m. melanochir, P. multifilis Schlegel in
Temminck and Schlegel, 1843, and P. paradiseus.
Polynemus aquilonaris and P. dubius are easily distinguished from P. multifilis by having seven pectoral filaments(14–16 in the latter; Feltes, 2002). Furthermore, the former
two species differ from P. hornadayi and P. paradiseus inhaving a greater number of first dorsal-fin spines (8; seeMotomura et al., 2002b: fig. 3C; Tables 1, 2 vs. 7 in the lattertwo species; see Motomura et al., 2002b: fig. 3AB, tables 1, 2)
and anal-fin spines (3; Tables 1, 2 vs. 2 in P. paradiseus;
Motomura et al., 2002b: tables 2, 3), a lower number of
pored lateral-line scales (80–86 in P. aquilonaris and 69–79
in P. dubius; Tables 1–3, vs. 90–103 in P. hornadayi;
Motomura et al., 2002b: tables 1, 4), and the sixth or seventh
pectoral filaments longest (fifth longest in P. hornadayi;
Motomura et al., 2002b).
Polynemus melanochir dulcis and P. m. melanochir lackvilliform teeth on the vomer and have black pigmentationon (usually) more than half of the posterior margin of
the pectoral fins (Motomura and Sabaj, 2002), whereas P.
aquilonaris and P. dubius have villiform vomerine teeth andlack black pigmentation on the pectoral fins. Furthermore,
P. aquilonaris and P. dubius differ from both the aforementioned subspecies in having longer pectoral-fin rays [34–41% (mean 37%) of SL in P. aquilonaris and 34–40% (37%)
in P. dubius; Tables 1, 2, vs. 31–35% (33%) in P. m. dulcis and
30–35% (32%) in P. m. melanochir; see Motomura andSabaj, 2002: tables 1, 2] and pectoral filaments [longest filament 260–371% (308%) in P. aquilonaris and 264–312%(293%) in P. dubius; Tables 1, 2, vs. 128–153% (141%) and
141–193% (159%), respectively; Motomura and Sabaj, 2002:
tables 1, 2].
Although P. aquilonaris is very similar to P. dubius, theformer can be clearly distinguished from the latter by having higher counts of pored lateral-line scales [80–86 (mode81) vs. 69–79 (78) in the latter] and scale rows below the

H. Motomura

lateral line [14–17 (mode 14, rarely 13 or 17) vs. 13 (rarely12)], and lower counts of gill rakers [9–11 (mode 11) inupper series, 16–18 (17) in lower, and 25–29 (27) total vs. 11–
13 (12), 18–21 (18), and 29–33 (30), respectively] (see Table3). Furthermore, P. aquilonaris differs from P. dubius inhaving a slightly higher second dorsal-fin soft ray count (15–
19 vs. 14–16 in the latter) and lower pectoral-fin ray counts(15–17 vs. 16–18) (see Table 3).
Comparative
material
examined. Polynemus
melanochirmelanochir: RMNH 34454 (2 specimens; formerly RMNH 6014), 61–
107 mm SL, data unknown.
Acknowledgments I greatly appreciate receiving specimen loans fromthe following: M.H. Sabaj (ANSP); J. Maclaine (BMNH); K. Sasaki
and Y. Machida (BSKU); M.A. Rogers and K. Swagel (FMNH); S.O.
Kullander (NRM); K. Matsuura and G. Shinohara (NSMT); M.J.P. van
Oijen and J. van Egmond (RMNH); D.W. Nelson (UMMZ); T. Yoshino(URM); S. Morrison (WAM); I.J.H. Isbrücker (ZMA); P.K.L. Ng
and K.K.P. Lim (ZRC). I am especially grateful to M.J.P. van Oijen(RMNH) for his translation of Bleeker’s paper into English, and M.H.
Sabaj (ANSP) and Y. Tohyama (Yokohama, Japan) for kindly providing their color photographs of Polynemus aquilonaris. I thank Y.
Motomura (Sydney, Australia) for her assistance and G.S. Hardy(Ngunguru, New Zealand), who read the initial manuscript and offeredhelpful comments. This study was supported in part by a grant awarded
to the author by Research Fellowships of the Japan Society for the
Promotion of Science for Young Scientists (Tokyo, Japan).

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