A new species, Polydactylus siamensis, from Thailand andredescription of P. plebeius (Broussonet, 1782) withdesignation of a neotype (Perciformes: Polynemidae)
Hiroyuki Motomura1,*, Yukio Iwatsuki2, and Tetsuo Yoshino3
1

Miyazaki University, the United Graduate School of Agricultural Sciences, Kagoshima University, 1-1 Gakuen-kibanadai-nishi,
Miyazaki 889-2192, Japan (e-mail: a02113u@cc.miyazaki-u.ac.jp)
2
Division of Fisheries Sciences, Faculty of Agriculture, Miyazaki University, 1-1 Gakuen-kibanadai-nishi, Miyazaki 889-2192,
Japan (e-mail: yuk@cc.miyazaki-u.ac.jp)
3
Department of Marine Sciences, Faculty of Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan(e-mail: b985005@sci.u-ryukyu.ac.jp)
Received: January 12, 2000 / Revised: September 15, 2000 / Accepted: January 12, 2001

IchthyologicalResearch©The Ichthyological Society of Japan 2001

Ichthyol Res (2001) 48: 117–126

Abstract A new species, Polydactylus siamensis, is described on the basis of eight specimens from Thailand. The species is similar to P. plebeius (Broussonet, 1782) in having fivepectoral filaments and several dark stripes along the scale rows above and below the lateralline, but differs from the latter in having lower counts of pectoral fin rays (15 vs. 16–18 in P.
plebeius), pored lateral line scales (54–58 vs. 60–68), scale rows above and below the lateralline (7 and 10 or 11, respectively vs. 8 or 9 and 12 or 13, respectively) and gill rakers (9 or
10 upper series, 13 or 14 lower and 22–24 total vs. 9–14, 13–18 and 24–32, respectively), anda longer upper jaw (mean 17% [range 16–17%] of standard length vs. 15% [13–16%]).
Polydactylus siamensis is currently known only from Bangkok and Songkhla, Gulf ofThailand, and Phuket Island, Andaman Sea, whereas P. plebeius is widely distributed in the
Indo-Pacific.
Key words Polynemidae · New species · Polydactylus siamensis · Redescription ·Polydactylus plebeiusT

he polynemid fish, Polydactylus plebeius, which is
the oldest available name for Indo-Pacific species
in that genus, was originally reported by Broussonet(1782) from Tahiti, Society Islands, Polynesia. The species
is characterized by five pectoral filaments and several
prominent dark stripes along the longitudinal scale rows
above and below the lateral line (e.g. Day, 1876; Menon,
1974; Talwar and Jhingran, 1992).
Recently, eight examples of a second polynemid species, also with five pectoral filaments and longitudinaldark stripes on the lateral body surface, were identified inmuseum collections, the specimens having been collected
only from Thailand: Bangkok and Songkhla (Gulf ofThailand) and Phuket Island (Andaman Sea). The specimens, which were very similar to P. plebeius in overall
body appearance, clearly differed from the latter in several aspects, including lateral line scale counts, scale rows
above and below the lateral line, gill raker counts, pectoral fin ray counts and upper jaw length. Furthermore,
seven other nominal species with five pectoral filaments
and longitudinal dark stripes on the body were examined,
resulting in the Thailand specimens being considered torepresent an undescribed species of Polydactylus.

This article includes a description of the new species
and a redescription of P. plebeius, based on the types anda wide range of non-type material. In addition, a neotype
is designated for P. plebeius.

Methods
Counts and measurements generally follow Hubbs
and Lagler (1958) and Feltes (1991), with somemodifications following Motomura et al. (2000). Standard length is expressed as SL. Terminology of thesupraneural bones follows Mabee (1988), and the formula for configuration of the supraneural bones, anterior
neural spines, and anterior dorsal fin pterygiophores
follows Ahlstrom et al. (1976). The configuration of
supraneural bones and vertebrae counts were checkedby X-ray photos. Institutional codes follow Leviton et al.
(1985), with additional institutional abbreviations as follows: Division of Fisheries Sciences, Miyazaki University,
Japan (MUFS); Phuket Marine Biological Center, Thailand (PMBC); and Shanghai Fisheries University, China(SFU).

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H. Motomura et al.

Fig. 1. A Neotype of Polydactylus plebeius, FMNH 108655, 88 mm SL, Tahiti. B Holotype of P. siamensis sp. nov., URM-P 14050,
252 mm SL, Thailand

Polydactylus plebeius (Broussonet, 1782)(English name: striped threadfin)(Japanese name: tsubame-konoshiro)(Fig. 1A)
Polynemus plebeius Broussonet, 1782: described on 27th
page from a table of contents, 8th plate (7th species) (nopagination) (type locality: Tahiti, Society Islands and Tanna
Island, New Hebrides Islands, Vanuatu); Bleeker, 1849: 58(Indonesia); Cantor, 1849: 1009 (Malay Peninsula); Day,
1876: 179 (India); Munro, 1955: 97 (Ceylon); Kagwade, 1970:
44 (India); Menon, 1974: POLYN Poly 2 (eastern Indian
Ocean and western central Pacific); Jones and Kumaran,
1980: 199 (Laccadive Archipelago, India); Menon and Babu
Rao, 1984: POLYN Poly 2 (western Indian Ocean).
Polynemus emoi Lacepède, 1803: 410, 412 (type locality:
Tahiti, Society Islands, replacement name for P. plebeius
Broussonet).
Polynemus lineatus Lacepède, 1803: 410, pl. 13, fig. 2 (typelocality: Réunion Island, Mascarene Islands).
Polynemus niloticus Shaw, 1804: 151 (type locality: Nile River,
Africa [but probably erroneous; see Remarks], based on
figure and description by J. Bruce).

Polynemus commersonii Shaw, 1804: 156 (type locality: Indianseas, based on figure by P. Commerson; replacement namefor P. lineatus Lacepède).
Polynemus lineatus Günther, 1860 (not of Lacepède): 327 (typelocality: Ambon, Indonesia and Guadalcanal, Solomon
Islands, primary homonym of P. lineatus Lacepède).
Polynemus taeniatus Günther, 1860: 526 (type locality: Ambon,
Indonesia and Guadalcanal, Solomon Islands, replacement
name for P. lineatus Günther).
Trichidion plebejus (sic); Gill, 1861: 276 (east Indian sea, list
only).
Polydactylus agonasi Jordan and McGregor, 1906: 814, unnumbered figure on page 815 (type locality: Tokyo, Japan).
Polynemus plebejus (sic); Weber and de Beaufort, 1922: 202(Indo-Australian Archipelago); Marshall, 1964: 416, pl. 56, fig.
402 (Queensland, Australia).
Polydactylus plebejus (sic); Fowler, 1935: 282, fig. 60 (HongKong, China); Grant, 1982: 534, unnumbered figure on page534 (Queensland and northern New South Wales, Australia).
Polynemus lydiae Curtiss, 1938: 43 (type locality: Tahiti, Society
Islands).
Polydactylus plebeius; Smith, 1949: 327, fig. 898 (South Africa);
Munro, 1967: 191, pl. 21, fig. 326 (New Guinea); Shen, 1984:
98, fig. 361–3a (in part; northeastern and southwestern parts

A new polynemid species and redescriptionof Taiwan); Gloerfelt-Tarp and Kailola, 1984: 231, photo second from bottom on page 230 (southern Indonesia); Smith,
1986: 721, fig. 223.2 (South Africa); Talwar and Jhingran,1992: 909 (India, key only); van der Elst, 1993: 278, unnumbered figure (South Africa); Senou, 1995: 847 (southern
Japan); Fricke, 1999: 305 (Mascarene Islands).
Trichidion plebejum (sic); Bleeker, 1983: 22, pl. 455, fig. 3 (locality not provided, originally Polynemat pl. 3, unpublishedplate by P. Bleeker).
Neotype. FMNH 108655, 88 mm SL, Tahiti, Society Islands,
6 Feb. 1962, collected by A. R. Watkins.
Other material (n 5 114, 43–331 mm SL). AMS I. 10581,
119 mm SL, Manila, Luzon Island, Philippines; AMS IB. 2329,
117 mm SL, Geraldton District, Western Australia, Australia;
BMNH 1855.11.7.35 (1 of 2 syntypes of Polynemus taeniatus
Günther, 1860), 139 mm SL, Guadalcanal, Solomon Islands;
BMNH 1858.4.21.85 (1 of 2 syntypes of P. taeniatus Günther,
1860), 147 mm SL, Ambon, Indonesia; BMNH 1899.1.24.8,
200 mm SL, Pakistan; BMNH 1913.4.7.137, 225 mm SL,
Mombasa, Kenya; BPBM 8433, 80 mm SL, Papara, Tahiti, Society Islands; BPBM 35868, 171 mm SL, Grindstone, Rahah Bay,
Oman (16°579 N, 54°499 E); BSKU 25698, 205 mm SL, Colombo
market, Sri Lanka; BSKU 45336, 148 mm SL, Kochi, Japan;
FMNH 21441, 210 mm SL, Tahiti, Society Islands; FMNH 91473(15 specimens), 53–127 mm SL, Tahiti, Society Islands; FRLM
1624, 6681–6682, 9815, 11357, 13712–13714 (8), 95–245 mm SL,
Goza, Shima, Mie, Japan; FRLM 23422, 57 mm SL, Tantui, Ambon, Indonesia; MNHN A. 5440 (holotype of P. lineatus
Lacepède, 1803), 255 mm SL, Reunion Island, Mascarene Islands; MUFS 1394, 12731 (2), 186–309 mm SL, Miyazaki, Japan;
MUFS 12982–12985 (4), 164–187 mm SL, Totoro, Nobeoka,
Miyazaki, Japan; MUFS 14110, 14125–14126 (3), 143–160 mm
SL, Meitsu, Nango, Miyazaki, Japan; MUFS 14201–14201 (2),271–323 mm SL, Noumea, New Caledonia; MUFS 14315, 14349,
14351 (3), 161–172 mm SL, Meitsu, Nango, Miyazaki, Japan;
MUFS 14480, 180 mm SL, Phuket Island, Thailand; MUFS
15760–15761 (2), 203–209 mm SL, Kushima, Miyazaki, Japan;
MUFS 15762, 15765 (2), 205–238 mm SL, Oshima, Meitsu,
Nango, Miyazaki, Japan; MUFS 15775, 233 mm SL, Kushima,
Miyazaki, Japan; MUFS 16829–16830, 16834 (3), 118–130 mm
SL, Kalairt fish landing port, Chennai (5Madras), India; MUFS
16849, 16851–16852 (3), 103–111 mm SL, Shanmugam fish
market, Chennai (5Madras), India; MUFS 19063, 71 mm SL,
Shankarpur landing center, Midnapore, Calcutta, India; NSMTP 783, 131 mm SL, Tokyo fish market, Tokyo, Japan; NSMT-P
19247, 119 mm SL, off Ito, Shizuoka, Japan; NSMT-P 23943 (2),
195–223 mm SL, Ishigaki Island, Ryukyu Islands, Japan; NSMTP 29332, 56 mm SL, Okinawa Island, Japan; NSMT-P 53857,
51 mm SL, Kuta, southern coast of Lombok Island, Indonesia;
NSMT-P 53918, 53920 (2), 46–56 mm SL, Gerupuk, southerncoast of Lombok Island, Indonesia; NSMT-P 54111, 48 mm SL,
Hamajima, Mie, Japan; PMBC 5922, 234 mm SL, Phuket Island,
Thailand; SAM 12076, 198 mm SL, East London, South Africa;
SAM 18448, 166 mm SL, Natal, South Africa; SAM 19747,
76 mm SL, East London, South Africa; SFU 3832, 171 mm SL,
Hong Kong, China; SFU 10031, 173 mm SL, Hainan Island,
China; UMMZ 171715, 98 mm SL, Indonesia; URM-P 701, 877(2), 148–166 mm SL, Okinawa Island, Japan; URM-P 3048,
331 mm SL, Chinen fish market, Okinawa Island, Japan; URM-P
6227, 149 mm SL, Okinawa Island, Japan; URM-P 24672, 24675,
24677–24678, 24680–24682, 25025–25026 (9), 132–180 mm SL,
Nakagusuku fish market, Okinawa Island, Japan; USNM 30503,

119
252 mm SL, New Guinea; USNM 55608 (holotype of
Polydactylus agonasi Jordan & McGregor, 1906), 155 mm SL,Tokyo, Japan; USNM 56398 (3), 135–138 mm SL, Tokyo, Japan;
USNM 86575, 189 mm SL, Mauritius; USNM 106889, 112 mm
SL, Honolulu, Hawaii; USNM 112734, 175 mm SL, Suva, Fiji
Islands; USNM 115739, 79 mm SL, Pagai, Samoa; USNM
226566, 108 mm SL, Santo, New Hebrides; USNM 278193,
192 mm SL, mouth of Rewa River, Fiji Islands (18°099 S, 178°329
E); USNM 278216 (2), 47–58 mm SL, Peu, Vanikoro Island,
Santa Cruz Islands (11°429 S, 166°509 E); USNM 278220, 43 mm
SL, Madagascar (13°18.429 S, 48°9.159 E); USNM 349503, 60 mm
SL, Mauritius (20°21.219 S, 57°449 E); YCM-P 44, 85 mm SL,
Nobikaigan, Yokosuka, Kanagawa, Japan; YCM-P 133, 144 mm
SL, Manazuru fish market, Kanagawa, Japan; YCM-P 25293 (3),103–150 mm SL, Ogasawara Islands, Japan; YCM-P 25328 (2),
108–148 mm SL, Ogasawara Islands, Japan.

Diagnosis. A species of Polydactylus with the following combination of characters: 5 pectoral filaments; 16–
18 (rarely 15, 1 of 100 specimens) pectoral fin rays; 60–66(rarely 68, 1 of 96 specimens) pored lateral line scales; 8
or 9 scale rows above lateral line, 12 or 13 below; 9 to 14
upper series gill rakers, 13–18 lower, 24–32 total; upper
jaw short (mean 15% [range 13–16%] of SL); 7 or 8
prominent dark stripes along longitudinal scale rows
above lateral line, 7 to 9 faint stripes below (occasionallylost in older preserved specimens).
Description. Counts and proportional measurements as percentages of SL of the neotype and othermaterial of Polydactylus plebeius are given in Table 1.
When different from the neotype, data for other specimens are given in parentheses. Characters given in the
diagnosis are not repeated.
Body oblong, compressed; maxilla covered with scales;
orbit diameter greater than snout length; lower lip welldeveloped; posterior margin of maxilla reaching to (orslightly beyond) level of posterior margin of adipose
eyelid; depth of posterior portion of maxilla shorter thandermal eye opening; teeth villiform in broad bands onvomer, palatines and ectopterygoids; all pectoral fin rays
unbranched; tip of fifth pectoral filament extending beyond posterior tip of pelvic fin; thickness of base of all
first dorsal fin spines similar; second dorsal fin base andanal fin base similar; between pelvic fin and anal fin bases
less than head length; lateral line simple, extending toupper end of lower caudal fin lobe; formula for configuration of supraneural bones, anterior neural spines andanterior dorsal pterygiophores 0/0/012/111/1/1/1/1/;
vertebrae 10 1 14; swimbladder simple, elongated.
Color in life.—Based on color transparencies andobservations of all specimens collected from Miyazaki
Prefecture, southern Japan: head and upper sides oftrunk tinged slightly blackish-silver, becoming lighter silver on lower sides; abdominal region white; snout semitransparent; first and second dorsal fins and caudal fin

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H. Motomura et al.

Table 1. Counts and measurements of Polydactylus plebeius, including the neotype, other nominal types and non-type specimens,
expressed as percentages of standard length

Standard length (mm)Fork length (mm)Counts
Dorsal fin rays
Anal fin rays
Pectoral fin rays
Pectoral filaments
Pelvic fin rays
Pored lateral line scales
Scales above and below lateralline
Gill rakers
Measurements
Head length
Body depth
Second body depth
Body width at pectoral fin base
Snout length
Dermal eye opening
Orbit diameter
Interorbital width
Postorbital length
Upper jaw lengthPre-1st dorsal fin lengthPre-2nd dorsal fin length
Preanal fin length
First dorsal fin origin to anal
fin origin
Pelvic fin origin to anal fin
originSecond dorsal fin base length
Anal fin base length
Longest pectoral fin length
Longest pectoral filament
length (5th)Pectoral fin base length
Longest pelvic fin ray length(1st)Longest 1st dorsal fin spine
length (3rd)Second dorsal fin spine length
Longest 2nd dorsal fin ray
length (2nd)Longest anal fin spine length(3rd)Longest anal fin ray length(2nd)
Caudal peduncle length
Caudal peduncle depth
Upper caudal fin lobe length
Lower caudal fin lobe length

Neotype of
Polydactylus
plebeius
FMNH
108655

Holotype of
Polynemus
lineatus
MNHN A.
5440 (dried
specimen)

Syntypes of
Polynemus taeniatus
BMNH
1855.11.7.35 and1858.4.21.85(n 5 2)

Holotype of Non-type specimens
Polydactylus (n 5 109)
agonasi
USNM 55608

88
100

254
279

139–147
156–164

155
178

43–331
50–365

VIII-I, 13
III, 11
18
5
I, 5
63
8 / 12

BrokenIII, 11
16
5
I, 5
63
—

VIII-I, 13
III, 11
17
5
I, 5
62–66
8–9 / 12

VIII-I, 13
III, 11
17
5
I, 5
65
9 / 13

VIII-I, 12–13
III, 11–12
15–18
5
I, 5
60–68
8–9 / 12–13

11 1 14 5 25—

11 1 14–16 5 25–27

11 1 14 5 25

9–14 1 13–18 5 24–32

32
30
29
15
6
8
9
10
18
16
38
62
62
40

28
28
28
—
BrokenBrokenBroken
—
16
15
35
62
69
42

30–32
27–30
29–33
12
5–6
7–8
8–9
8–9
17–18
14
36–37
61
61–62
42–44

31
29
32
14
5
7
8
9
18
15
36
61
64
43

25–34 (31)
25–32 (28)
25–34 (30)
11–17 (14)
5–9 (6)
5–9 (7)
7–11 (9)7–10 (8)15–20 (18)
13–16 (15)33–38 (36)
57–63 (61)59–67 (63)37–45 (42)

24

26

24–27

25

22–28 (25)

16
16
20
39

16
15
20
Broken

15–18
16–17
20–22
35–42

18
17
23
31

15–19 (17)
14–18 (16)17–28 (20)
22–40 (32)917Broken
15

10–11
15–17

9
16

9–11 (9)15–19 (16)

21

19

22

21

17–24 (21)

9
22

7
20

9
24–28

8
21

6–10 (8)19–28 (22)8

Broken8–9

9

6–10 (8)

14

17

23

Broken17–23 (19)

26
14
39
35

23
13
37
33

25–26
14–15
41–43
40

25
15
37
35

23–27 (25)
12–16 (14)33–44 (39)
30–41 (36)Means in parentheses include data of type specimens

A new polynemid species and redescription

121

Fig. 2. Localities of specimens of Polydactylus plebeius (d) and P. siamensis sp. nov. (★) examined in the present study

pale with blackish posterior margins; pectoral fin membrane blackish; pectoral filaments white; anterior margins and origins of pelvic and anal fins white, other parts
dusky yellowish-white; seven or eight prominent dark
stripes along scale rows above lateral line, seven to ninefaint stripes below.
Color of preserved specimens.—Based on neotype:head and upper sides of trunk tinged slightly blackishbrown, becoming lighter brown on lower sides; sevenfaint dark stripes along scale rows above lateral line;
anterior margins of first and second dorsal fins blackish,posterior margins whitish and blackish, respectively,
elsewhere blackish-brown; pelvic and anal fins blackishbrown, posterior portion whitish; caudal fin blackishbrown, darkening posteriorly; pectoral fin blackish;pectoral filaments pale brown.
Distribution and ecological notes. Polydactylus
plebeius is widely distributed in the Indo-Pacific; including South Africa, Madagascar, Mauritius, Oman, India,
Sri Lanka, Thailand, Indonesia, Philippines, Papua New
Guinea, Australia, Solomon Islands, Vanuatu, New
Caledonia, Fiji, Samoa, Tahiti, China, Japan and Hawaii(based on specimens examined during this study, Fig. 2).
Other distributional locations of the species have beenreported off Bangladesh, Myanmar, Malaysia, Brunei,
Cambodia and Vietnam (Menon, 1974) and off
Mozambique, in the Red Sea and off Pakistan (Menonand Babu Rao, 1984).
Examples of P. plebeius examined here were collectedalong shallow, sandy or muddy coastal beaches, as well as
in estuaries. The species also occurs offshore in Miyazaki,
southern Japan during the rainy (June and July) andtyphoon seasons (September and October) (the first andsecond authors, personal observations). Apparently P.
plebeius usually inhabits estuaries and shallow coastal
waters but departs the former during periods of highrainfall.
Remarks. Polynemus (5Polydactylus) plebeius,
which is widely distributed in the Indo-Pacific, wasoriginally described by Broussonet (1782) from Tahiti,
Society Islands and Tanna Island, New Hebrides Islands,
Vanuatu. According to A.-M. Hine (BMNH), thesyntypes of P. plebeius have apparently been lost.
Although the original description of P. plebeius is very
poor, the figure clearly shows 16 pectoral fin rays, 5 pectoral filaments and several longitudinal dark stripes
along each scale row on the lateral body surface.
The holotype (a dried specimen) of Polynemus
lineatus Lacepède, 1803, both syntypes of P. taeniatus
Günther, 1860 and the holotype of Polydactylus agonasi
Jordan and McGregor, 1906 were all found to beconspecific, being the same species as the specimens considered here as P. plebeius. Their meristic and morphological characters are included in Table 1. Günther (1860)
described Polynemus lineatus as a new species on thebasis of two specimens from Ambon, Indonesia andGuadalcanal, Solomon Islands. Because that name waspreoccupied by P. lineatus of Lacepède (1803), Günther(1860) proposed a replacement name, P. taeniatus, in an
addenda to the original description of the species. In
addition, Günther (1860) described P. plebejus (sic)(5plebeius) as being characterized by five pectoral filaments and a black blotch on the lateral line near its
origin. Because the characters for P. plebejus given by
Günther (1860) agree with those diagnostic of Polydactylus microstomus (Bleeker, 1851) (see Munro, 1967: 191;

122

Menon and Babu Rao, 1984: POLYN Poly 6), it is considered that he had misidentified examples of the latter.
Lacepède (1803) proposed a new name, Polynemus
emoi, for P. plebeius Broussonet, 1782, but did not list
any specimens. The former name has no standing in nomenclature, because the principle of priority was notfollowed, contrary to the requirements of Article 23(ICZN, 1999).
Polynemus niloticus was described by Shaw (1804) as a
new species from the Nile River, on the basis of a description and figure by J. Bruce. In fact, the latter had
observed the species on the border of the Red Sea, buterroneously described it as being from the Nile River(McClelland, 1843). According to Shaw (1804), the species had a unique character, being a reddish snout. If
damaged, however, the cartilaginous tissue of the snoutof polynemid fishes is easily congested, as evidenced by areddish coloration, owing to its semitransparent nature.
Polynemus niloticus is considered conspecific with
Polydactylus plebeius, owing to the number of pectoral
filaments (5) and [corrected] type locality (Red Sea) of
the former (Cantor, 1849; Daget and Njock, 1986; thisstudy). Furthermore, Shaw (1804) proposed P. commersonii as a replacement name for P. lineatus Lacepède,
1803. The former name has no standing in nomenclature
for the same reason as given earlier for P. emoi.
Polynemus lydiae was described by Curtiss (1938) as a
new species from Tahiti, Society Islands. The originaldescription of the species was very poor and gave no
indication of type specimens. Enquiries established thatno types of that species are held in MNHN (P. Pruvost,
personal communication). According to the original description, the species was characterized by five pectoral
filaments and longitudinal black stripes on the lateralbody surface, characteristics being consistent with thoseof Polydactylus plebeius. All the Tahitian specimens(n 5 18, 53–210 mm SL) examined during this study represented a single species, P. plebeius. Therefore, we are of
the opinion that Polynemus lydiae should be regarded asa junior synonym of Polydactylus plebeius.
Fricke (1999) was synonymized Sciaena pentadactyla
Lacepède, 1802 with P. plebeius. Furthermore, he designated a original figure of P. plebeius as neotype for theformer in his faunal work of the Mascarene Islands because no type material of S. pentadactyla could be detected. However, this was done simply as a matter offaunal work (not a revisory work), such an action being
expressly prohibited by Article 75.2 (ICZN, 1999) andwas considered to be an invalid designation. We examined the original description of S. pentadactyla byLacepède (1802) who described the following charactersof the species: 7 first dorsal fin rays, 10 second dorsal fin
rays, 5 rays in every abdominal (probably meaning 5

H. Motomura et al.

pelvic fin rays), 10 anal fin rays, caudal fin rounded, aspine present in anterior (probably meaning upper tip)of opercular, pectoral fin very large, and lateral line insensible. All these characters, except for a spine of theupper tip of the opercular, did not totally agree with thecharacters of P. plebeius, which had the following characters: 8 first dorsal fin spines, 13 or 14 second dorsal fin
rays (including a spine), 6 pelvic fin rays (including aspine), 14 or 15 anal fin rays (including 3 spines), caudal
fin deeply forked, pectoral fin not very large and lateralline not insensible. Accordingly, we strongly believe that
S. pentadactyla is not a junior synonym of P. plebeius,although the taxonomic status of the former is still unknown (the former is herein treated as nomen dubium).
Recently, a figure of Polynemus plebeius in the originaldescription was designated as the lectotype of the species
by Fricke (1999). However, the lectotype was not designated on the basis of a specimen, such a case being expressly treated as an invalid designation by Article 72(ICZN, 1999). The proposal of a neotype for P. plebeius(Broussonet, 1782) is herein justified to avoid taxonomic
confusion because P. plebeius is very similar to the following new species and the syntypes of P. plebeius haveapparently been lost. Accordingly, a specimen (FMNH
108655, 88 mm SL) collected from the same locality,
Tahiti, is herein proposed as a neotype for the species.

Polydactylus siamensis sp. nov.
(New English name: large mouth striped threadfin)(Fig. 1B)
Holotype. URM-P 14050, female, 252 mm SL, Samyan
market, Bangkok, Thailand, 14 Feb. 1984, collected by H.
Senou.
Paratype. MUFS 18280, sex undetermined, 137 mm SL,
Samyan market, Bangkok, Thailand, 26 Nov. 1983, collected by
H. Senou.
Other material (n 5 6, 128–239 mm SL). PMBC 5917–5921(5 specimens), 128–239 mm SL, Phuket Island, Thailand; Princeof Songkhla University uncatalogued, 174 mm SL, Hat Yai fish
market, Songkhla, Thailand.

Diagnosis. A species of Polydactylus with the following combination of characters: 5 pectoral filaments; 15
pectoral fin rays; 54–58 pored lateral line scales; 7 scales
above lateral line, 10 or 11 below; 9 or 10 upper series gillrakers, 13 or 14 lower, 22–24 total; upper jaw large (mean
17% [range 16–17%] of SL); 7 or 8 prominent dark
stripes along scale rows above lateral line, 7 to 9 faintstripes below (occasionally lost in older preserved
specimens).
Description. Counts and proportional measurements as percentages of SL of the holotype, paratypeA new polynemid species and redescription

123

Table 2. Counts and measurements of Polydactylus siamensis sp. nov., including the holotype, paratype and non-type specimens,
expressed as percentages of standard length

Standard length (mm)Fork length (mm)Counts
Dorsal fin rays
Anal fin rays
Pectoral fin rays
Pectoral filaments
Pelvic fin rays
Pored lateral line scales
Scales above and below lateral line
Gill rakers
Measurements
Head length
Body depth
Second body depth
Body width at pectoral fin base
Snout length
Dermal eye opening
Orbit diameter
Interorbital width
Postorbital length
Upper jaw lengthPre-1st dorsal fin lengthPre-2nd dorsal fin length
Preanal fin length
First dorsal fin origin to anal fin origin
Pelvic fin origin to anal fin origin
Second dorsal fin base length
Anal fin base length
Longest pectoral fin length
Longest pectoral filament length (5th)Pectoral fin baseLongest pelvic fin ray length (1st)Longest 1st dorsal fin spine length (3rd)Second dorsal fin spine length
Longest 2nd dorsal fin ray length (2nd)Longest anal fin spine length (3rd)Longest anal fin ray length (2nd)Caudal peduncle length
Caudal peduncle depth
Upper caudal fin lobe length
Lower caudal fin lobe length

Holotype
URM-P 14050

Paratype
MUFS 18280

Non-type specimens(n 5 6)

252
274

137
153

128–239
144–263

VIII-I, 13
III, 11
15
5
I, 5
58
7 / 119 1 13 5 22

VIII-I, 13
III, 11
15
5
I, 5
54
7 / 10
10 1 13 5 23

VIII-I, 12–13
III, 11
15
5
I, 5
54–57
7 / 11
10 1 13–14 5 23–24

31
33
34
16
7
7
8
7
20
16
37
63
68
44
29
17
15
20
34
11
16
19
7
21
7
19
24
15
37
33

32
30
31
16
7
7
8
8
20
16
37
60
65
43
26
18
17
22
35
10
16
21
9
21
8
20
25
15
41
35

31–34 (32)
30–33 (32)
31–33 (32)
15–18 (16)
5–8 (6)
7–8 (7)
8–9 (8)
8–9 (8)
19–21 (20)
16–17 (17)37–40 (38)
62–66 (64)
64–68 (66)
42–45 (44)22–28 (26)
15–17 (17)
14–17 (16)
20–22 (21)31–43 (36)
10–11 (11)
16–17 (16)
19–23 (21)
7–9 (8)22–24 (23)
8–11 (9)20–23 (21)22–25 (24)
14–16 (15)38–41 (40)
34–37 (35)Means in parentheses include data of type specimens

and other material of Polydactylus siamensis sp. nov. aregiven in Table 2. When different from the holotype,
data for paratype and non-type specimens are given inparentheses. Characters given in the diagnosis are notrepeated.
Body oblong, compressed; maxilla covered with scales;
orbit diameter greater than snout length; lower lip welldeveloped; posterior margin of maxilla slightly beyond
level of posterior margin of adipose eyelid; depth of posterior portion of maxilla shorter than dermal eye open-ing; teeth villiform in broad bands on vomer, palatinesand ectopterygoids; all pectoral fin rays unbranched; tipof fifth pectoral filaments not reaching to (reaching to or
extending slightly beyond) posterior tip of pelvic fin;thickness of base of all first dorsal fin spines similar;
second dorsal fin base slightly longer than anal fin base;between pelvic fin and anal fin bases less than headlength; lateral line simple, extending to upper end oflower caudal fin lobe; formula for configuration of
supraneural bones, anterior neural spines and anterior

124

H. Motomura et al.

dorsal pterygiophores 0/0/012/111/1/1/1/1/; vertebrae
10 1 14; swimbladder not observed.
Color of preserved specimens.—Based on holotype:head and upper sides of trunk tinged slightly cream, becoming white on lower sides; seven dark stripes along
scale rows above lateral line, stripes not apparent below;
snout region semitransparent; base and posterior portionof first and second dorsal fins light yellow, tips blackishbrown, otherwise whitish-cream; pelvic fin light yellow
posteriorly, otherwise whitish-cream; anal fin light yellow,
caudal fin posterior margin whitish-cream, otherwise
light yellow; pectoral fin membranes blackish; pectoral
filaments whitish.
Distribution and ecological note. Polydactylus
siamensis sp. nov. is currently known only from Bangkok,
Songkhla and Phuket, Thailand (Fig. 2), but is probably
more widely distributed about the Malay Peninsula. According to local fishermen at Bangkok, Samut Prakan
and Prachuap Khirikhan, Thailand, P. siamensis rarely
occurs in the Gulf of Thailand.
Etymology. The name of “siamensis” is based on
Siam, the old name for Thailand, in reference to theholotype locality.
Comparison. To date, only Polydactylus plebeius(Broussonet, 1782) has been recognized as having fivepectoral filaments and several prominent dark stripes
along the longitudinal scale rows above and below thelateral line. Although P. siamensis sp. nov. is very similar
to P. plebeius in having the above characters, the former
differs in having lower counts of pectoral fin rays (15 vs.
15–18 in the latter), scales above and below the lateralline (7 and 10 or 11, respectively vs. 8 or 9 and 12 or 13,
respectively), pored lateral line scales (54–58 vs. 60–68)
and gill rakers (9 or 10 upper series, 13 or 14 lower and
22–24 total vs. 9–14, 13–18, and 24–32, respectively)(Table 3). Furthermore, P. siamensis tends to have aslightly longer upper jaw than P. plebeius, although theproportional measurements for upper jaw length overlapped between the two species (Fig. 3).
Comparative material examined. Polydactylus macrochir(Günther): BMNH 1866.2.13.17 (holotype of Polynemus
macrochir), 171 mm SL, New South Wales, Australia (but probably Queensland; see Motomura et al., 2000). Polydactylus
microstomus (Bleeker): MUFS 14159, 154 mm SL, Ouenghi
River, New Caledonia. P. multiradiatus (Günther): FRLM
23414–23417 (4 specimens), 130–144 mm SL, Rumahtiga fish
market, Poka, Ambon, Indonesia. P. nigripinnis Munro: FRLM
21472, 139 mm SL, Ambon, Indonesia; FRLM 23413, 163 mm
SL, Rumahtiga fish market, Poka, Ambon, Indonesia. P. sexfilis(Valenciennes in Cuvier and Valenciennes): MNHN 9731 (lectotype of Polynemus sexfilis; see Motomura et al., 2001),

Table 3. Frequency distributions of selected meristic characters of Polydactylus plebeius and P. siamensis sp. nov.
Gill rakers
Upper
9
Polydactylus plebeius (n 5 97)
P. siamensis sp. nov. (n 5 8)

Lower
10

1
1b

11

12
a

4
7c

64
—

13

25
—

14

2
—

13

1
—

14
a

2
6bc

16
2

15

16

17

18

36
—

27
—

12
—

4
—

Gill rakers, total

Polydactylus plebeius (n 5 96)
P. siamensis sp. nov. (n 5 8)

22

23

24

25

26

27

28

29

30

31

32

1b

5c

2
2

16a
—

32
—

20
—

15
—

10
—

1
—

—
—

1
—

Pored lateral line scales

Polydactylus plebeius (n 5 96)
P. siamensis sp. nov. (n 5 8)

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

—
2c

—
1

—
2

—
2

—
1b

—
—

1
—

9
—

16
—

30a
—

21
—

8
—

10
—

—
—

1
—

Scales above and below lateral line

Polydactylus plebeius (n 5 90*)
P. siamensis sp. nov. (n 5 8)
a

7

8

9

—
8bc

65a
—

25
—

Neotype of P. plebeius
Holotype of P. siamensis sp. nov.
cParatype of P. siamensis sp. nov.
* Pectoral fin rays were counted on 100 examples of P. plebeiusb/

Pectoral fin rays

10

11

12

13

15

16

17

18

—
1c

—
7b

66a
—

24
—

1
8bc

9
—

66
—

24a
—

A new polynemid species and redescription

125
Thailand), M.N. Venugopal and A. Chakraborty (Departmentof Fishery Biology, College of Fisheries, India) and A.
Choochern (Bangkok, Thailand) for their assistance in fieldwork at various times. Last, we thank G.S. Hardy (Thames, New
Zealand), who read the initial manuscript and offered helpfulcomments and Y. Motomura (Miyazaki, Japan) for her assistance. This study was supported in part by grants awarded to
the first author by the Fujiwara Natural History Foundation(Tokyo, Japan), the Sasakawa Scientific Research Grant fromthe Japan Science Society (Tokyo, Japan) and the Ito Foundation for the Advancement of Ichthyology (Tokyo, Japan). This
paper is contribution number 38 from PMBC.

Literature Cited

Fig. 3. Relationship between standard length and upper jaw
length in Polydactylus plebeius and P. siamensis sp. nov.

265 mm SL, Mauritius; MNHN A. 3027, 9728 (2 paralectotypesof Polynemus sexfilis; see Motomura et al., 2001), 92–96 mm SL,
Mauritius. Polydactylus sextarius (Bloch and Schneider): ZMB
565 (holotype of Polynemus sextarius), 125 mm SL, Tranquebar,
India.
Acknowledgments We greatly appreciate the following persons and institutions for specimen loans: M. McGrouther and
K. Parkinson (AMS); J. Maclaine (BMNH); A.Y. Suzumoto(BPBM); Y. Machida and K. Sasaki (BSKU); M.A. Rogers and
K. Swagel (FMNH); S. Kimura (FRLM); K. Matsuura (NSMT);
U. Satapoomin (PMBC); L. Hoenson (SAM); H.-L. Wu (SFU);
D.W. Nelson (UMMZ); S.L. Jewett, L. Palmer and J.T. Williams(USNM); M. Hayashi (YCM); V. Lheknim (Faculty of Science,Prince of Songkhla University, Thailand). We are mostgrateful to A.-M. Hine (BMNH) for a loan of the syntypesof Polynemus taeniatus and information on the types of P.
commersonii, P. niloticus and P. plebeius, W.N. Eschmeyer(CAS) for providing the original description of P. lydiae, G.
Duhamel, J.-C. Hureau and P. Pruvost (MNHN) for opportunities to examine the type of P. lineatus, a loan of the syntypes ofP. sexfilis and information on the types of P. emoi and P. lydiae,
S.L. Jewett (USNM) for opportunities to examine the types of
Polydactylus agonasi, H.-J. Paepke (ZMB) for his provisionof type data and photographs of Polynemus sextarius and
H. Senou (Kanagawa Prefectural Museum of Natural History)
and M. Iwataki (Graduate School of Agricultural and Life
Science, University of Tokyo) for providing the originaldescription of P. plebeius. We thank V. Lheknim and P.
Pholpunthin (Faculty of Science, Prince of Songkhla University,

Ahlstrom EH, Butler JL, Sumida BY (1976) Pelagic
stromateoid fishes (Pisces, Perciformes) of the eastern
Pacific: kinds, distributions, and early life histories and observations on five of these from the Northwest Atlantic. Bull
Mar Sci 26:285–402
Bleeker P (1849) Bijdrage tot de kennis der Percoiden van
den Malaijo-Molukschen Archipel met beschrijving van 22
nieuwe soorten. Verh Batav Gen 22:1–64
Bleeker P (1983) Atlas ichthyologique des Indes OrientalesNéêrlandaises. Plates for planned tomes 11–14. Smithsonian
Institution Press, Washington, DC
Broussonet PMA (1782) Ichthyologia sistens piscium descriptiones et icones. Decas, London
Cantor TE (1849) Catalogue of Malayan fishes. J Asiat Soc
Bengal 18:xii 1 981–1443, 14 pls
Curtiss A (1938) A short zoology of Tahiti in the Society
Islands. Privately published. Zool Tahiti
Daget J, Njock JC (1986) Polynemidae. In: Daget J, Gosse J-P,
Thys van den Audenaerde DFE (eds) Check-list of the freshwater fishes of Africa, vol 2. ISNB, MRAC and ORSTOM,
Bruxelles, Tervuren and Paris, pp 352–354
Day F (1876) The fishes of India, being a natural history of thefishes known to inhabit the seas and fresh waters of India,
Burma, and Ceylon. Part 2. Bernard Quaritch, London
Feltes RM (1991) Revision of the polynemid fish genus
Filimanus, with the description of two new species. Copeia
1991:302–322
Fowler WH (1935) A synopsis of the fishes of China. Hong
Kong Naturalists 6:276–284
Fricke R (1999) Fishes of the Mascarene Islands (Réunion,
Mauritius, Rodriguez). An annotated checklist with descriptions of new species. Koeltz, Köenigstein
Gill T (1861) Synopsis of the polynematoids. Proc Acad Nat Sci
Phila 13:271–282
Gloerfelt-Tarp T, Kailola PJ (1984) Trawled fishes of southernIndonesia and northwestern Australia. Australian Development Assistance Bureau, Director General of Fisheries
Indonesia, German Agency Tech Coop, Jakarta
Grant EM (1982) Guide to fishes. Department of Harbours andMarine, Brisbane
Günther A (1860) Catalogue of the acanthopterygian fishes in
the collection of the British Museum (Natural History), vol 2.
Squamipinnes, Cirrhitidae, Triglidae, Trachinidae, Sciaenidae,
Polynemidae, Sphyraenidae, Trichiuridae, Scombridae,
Carangidae, Xiphiidae. British Museum, London
Hubbs CL, Lagler KF (1958) Fishes of the Great Lakes region.
Bull Cranbrook Inst Sci 26:1–213

126
ICZN (The International Commission on Zoological
Nomenclature) (1999) International code of zoological nomenclature, 4th edn, adopted by the General Assembly of
the International Union of Biological Sciences. International
Trust for Zoological Nomenclature, London
Jones S, Kumaran M (1980) Fishes of the Laccadive Archipelago. Mathrubhumi Press, Cochin
Jordan DS, McGregor RC (1906) Description of a new speciesof threadfin (family Polynemidae) from Japan. Proc US Natl
Mus 30:813–815
Kagwade PV (1970) The polynemid fishes of India. Bull CentMar Fish Res Inst 18:1–69
Lacepède BGE (1802) Histoire naturelle des poissons, vol 4.
Plassan, Paris
Lacepède BGE (1803) Histoire naturelle des poissons, vol 5.
Plassan, Paris
Leviton AE, Gibbs RH Jr, Heal E, Dawson CE (1985)
Standards in herpetology and ichthyology: Part I. Standard
symbolic codes for institutional resource collections in herpetology and ichthyology. Copeia 1985:802–832
Mabee PM (1988) Supraneural and predorsal bones in fishes:development and homologies. Copeia 1988:827–838
Marshall TC (1964) Fishes of the Great Barrier Reef andcoastal waters of Queensland. Angus and Robertson,
Sydney
McClelland J (1843) On East Indian Isinglass, its introduction
to, and manufacture for, the European market. J Nat HistCalcutta 3:157–188
Menon AGK (1974) Polynemidae. In: Fischer W, Whitehead
PJP (eds) FAO species identification sheets for fisherypurposes—eastern Indian Ocean and western central
Pacific. Fishing Area 57 and 71, vol 3. FAO, Rome, pp
1–2 1 “POLYN Eleu 1”–“POLYN Poly 5”
Menon AGK, Babu Rao M (1984) Polynemidae. In: Fischer W,
Bianchi G (eds) FAO species identification sheets for fisherypurposes—western Indian Ocean. Fishing Area 51, vol 3.

H. Motomura et al.
FAO, Rome, pp 1–2 1 “POLYN Eleu 1”–“POLYN Poly
7”
Motomura H, Iwatsuki Y, Kimura S, Yoshino T (2000) Redescription of Polydactylus macrochir (Günther, 1867), a seniorsynonym of P. sheridani (Macleay, 1884) (Perciformes:
Polynemidae). Ichthyol Res 47:327–333
Motomura H, Iwatsuki Y, Kimura S (2001) Redescription of
Polydactylus sexfilis (Valenciennes in Cuvier and Valenciennes, 1831), a senior synonym of P. kuru (Bleeker, 1853)
with designation of a lectotype (Perciformes: Polynemidae).
Ichthyol Res 48:83–89
Munro ISR (1955) The marine and freshwater fishes of Ceylon.
Department of External Affairs, Halstead Press, Canberra
and Sydney
Munro ISR (1967) The fishes of New Guinea. Department ofAgriculture, Stock and Fisheries, Port Moresby
Senou H (1995) Polynemidae. In: Nakabo T (ed) Fishes ofJapan with pictorial keys to the species (in Japanese). Tokai
University Press, Tokyo, pp 847, 1338–1339
Shaw G (1804) General zoology or systematic natural history,
vol 5. G. Kearsley, London
Shen S-C (1984) Coastal fishes of Taiwan. Shih-chieh Shen,
TaipeiSmith JLB (1949) The sea fishes of southern Africa. Central
News Agency Ltd, Cape Town
Smith MM (1986) Polynemidae. In: Smith MM, Heemstra
PC (eds) Smiths’ sea fishes. Macmillan South Africa,
Johannesburg, pp 720–721
Talwar PK, Jhingran AG (1992) Inland fishes of India andadjacent countries, vol 2. Balkema, Rotterdam
van der Elst R (1993) A guide to the common sea fishes ofsouthern Africa, 3rd edn. Struik, Cape Town
Weber MWC, de Beaufort LF (1922) The fishes of the IndoAustralian Archipelago, vol 4. Heteromi, Solenichthyes,
Synentognathi, Percesoces, Labyrinthici, Microcyprini. E.J.
Brill, Leiden