Bull. Natl. Mus. Nat. Sci., Ser. A, Suppl. 2, pp. 107–113, March 21, 2008

A New Sinistral Flounder, Engyprosopon kushimotoensis, from
Kushimoto, Kii Peninsula (Pleuronectiformes: Bothidae)
Kunio Amaoka1, Tatsuya Kaga1 and Hiroshi Misaki2
1

Hokkaido University, 3–1–1 Minato-cho, Hakodate, Hokkaido 041–8611, Japan
E-mail: amaoka@fish.hokudai.ac.jp
2
Kushimoto Marine Park Center, 1157 Arita, Kushimoto-cho, Nishimuro-gun, Wakayama 649–3514, Japan

Abstract A specimen of the genus Engyprosopon, washed ashore recently on a beach by atyphoon, is compared with its congeners and described as new to science. The new species compares well with other members of the genus, all of which share serrated gill rakers, uniserial teethon the upper jaw, and a small number of gill rakers. It differs from all previously described species
in having an extremely narrow interorbital width, a long pectoral fin on the right side and combinations of its proportional measurements and counts. A key to 7 species known from waters of Japanis provided.
Key words : Engyprosopon kushimotoensis sp. nov., key, Bothidae, Japan.

While undertaking a taxonomic review of thegenus Engyprosopon, we came across an unusual
specimen of the genus, found by the third author
on Sabiura beach in front of Kushimoto Aquarium, Kii Peninsula, following a typhoon. The
specimen, characterized by having an extremely
narrow interorbital space and a long pectoral finon the blind side, could not be identified with anyof the 27 recognized species of Engyprosopon(Fowler, 1934; Norman, 1934; Amaoka and Imamura, 1990; Hensley and Suzumoto, 1990;
Quero and Golani, 1990; Amaoka et al., 1993;
Amaoka and Mihara, 1995; Amaoka and Séret,2005a, 2005b). The species is herein described as
new to science. A key to Japanese species is also
provided.
The holotype and only known specimen isdeposited at the National Museum of Nature andScience (NSMT). Methods for making counts
and measurements follow those of Hubbs andLagler (1958) and Amaoka et al. (1993). Scaledefinitions follow those of Roberts (1993). Measurements were made with dial calipers anddividers to the nearest 0.1 mm. Vertebral counts
were made and the caudal skeleton examinedfrom radiographs. Type material of the following

species were examined: E. latifrons, E.
longipterum, E. natalensis, E. rostratum, E.
sechellensis, and E. septempes (for catalogue
numbers and locality data, see Amaoka et al.,1993). Institutional abbreviations follow Leviton
et al. (1985) except for the Kushimoto Marine
Park Center (KMPC).
Engyprosopon kushimotoensis sp. nov.
(New Japanese name: Kushimoto-darumagarei)(Figs. 1–4)
Holotype. NSMT-P 76957 (formerly KMPC-03081010), male, 58.9 mm SL, Kushimoto, Nishimuro-gun,
Wakayama Prefecture, washed ashore by typhoon, 3 August 2003.
Diagnosis. A species of the genus Engyprosopon distinguished from congeners in having uniserial teeth on theupper jaw, a small number of serrated gill rakers (07),
an extremely narrow interorbital width (7.76 in headlength), and a long pectoral fin on the blind side (1.81 inhead length).

Description. Counts and proportional measurements are given in Table 1. The following
morphometrics are expressed in percent of SL:
head length 27.7; body depth 51.4; snout length

108

K. Amaoka, T. Kaga and H. Misaki

Fig. 1. Engyprosopon kushimotoensis sp. nov., holotype, NSMT-P 76957, male, 58.9 mm SL, from Kushimoto,
Wakayama Prefecture, Japan. Scale indicates 10 mm.

5.9; upper eye diameter 9.0; lower eye diameter
9.2; interorbital width 3.6; upper jaw length on
ocular side 11.9, on blind side 12.1; lower jaw
length on ocular side 14.9, on blind side 15.1;
caudal peduncle depth 12.2; pectoral fin lengthon ocular side 18.7, on blind side 15.3; pelvic fin
length on ocular side 12.1, on blind side 11.9;
base of pelvic fin on ocular side 10.2, on blindside 3.4; length of longest dorsal fin ray 15.3;
length of longest anal fin ray 16.1; length of midcaudal fin ray 23.6.
Body oval, depth somewhat more than half
length of body, greatest depth slightly anterior to
mid-body; dorsal and ventral contours gently
arched. Caudal peduncle deep, depth less than
25% body depth.
Head large, length more than 25% SL; dorsal
profile gently arched, with a slight concavity anterior to the interorbital area. Snout long, slightly
protruding, length about 70% of eye diameter. A
prominent rostral spine present near tip of snout
just dorsal to tip of upper jaw. Eyes large, diameter more than 80% of upper jaw length; lower eye
placed slightly in advance of upper eye. Orbital
spine absent. Interorbital bone highly elevated,narrow, and deeply concave, width less than 50%

of eye diameter. Nostrils on ocular side situatedslightly ventral to midline, between and somewhat anterior to eyes; anterior nostril tubular,
with a flap directed posteriorly; nostrils on blindside small, placed below origin of dorsal fin, similar in shape to those on ocular side.
Mouth large, opening oblique; maxilla extending posteriorly to vertical through mid-point oflower eye; anterior tip of upper jaw projecting
beyond tip of lower jaw, when mouth closed.
Teeth on upper jaw sharp, uniserial, some at anterior tip of jaw enlarged; lower jaw teeth uniserial,
nearly equal in size and spacing to lateral teeth ofupper jaw. Scales deciduous, large; ocular-side
scales ctenoid, with short, peripheral ctenii oncentral posterior margin; scales cycloid on blindside (Fig. 3A). Gill rakers on lower limb of firstarch short, serrated, with few spines; gill rakers
absent on upper limb (Fig. 3B).
Pectoral fin of ocular side short, slightly lessthan 70% of head length; pectoral fin of blindside long, length about 82% of that of ocularside. Anteriormost ray of pelvic fin of ocular side
inserted at tip of isthmus, fourth pelvic-fin ray ofocular side opposite to first ray of blind-side
pelvic fin. Tip of isthmus at vertical through mid-

New Sinistral Flounder from Japan

109

Fig. 2. Engyprosopon kushimotoensis sp. nov., holotype, NSMT-P 76957, male, 58.9 mm SL, from Kushimoto,
Wakayama Prefecture, Japan. A: ocular-side body; B: blind-side trunk (B).

point of lower eye. Three upper- and lowermost
rays of caudal fin simple, remaining caudal rays
branched.
Coloration in alcohol: Ground color on ocular side grayish brown; posterior half of upper
jaw and area around eyes somewhat darker thanremaining surface; ground color on blind sidewith dark traces on body, head pale yellow. All
fins on ocular side grayish with traces of darker

spots.
Sexual dimorphism: The presence of a rostral spine and dark pigmentation on the blindside body (Figs. 1–2) are sexually dimorphic features that characterize males of other members of
the genus Engyprosopon. The holotype and only
known specimen of Engyprosopon kushimotoensis is a male.
Etymology. Named for the type locality,

Counts:
Dorsal-fin rays
Anal-fin rays
Pectoral-fin rays (O)Pectoral-fin rays (B)Pelvic-fin rays (O)Pelvic-fin rays (B)Caudal-fin rays
Scales in lateral line
Gill rakers first arch
Vertebrae

Morphometrics in HL:
Snout Length
Upper eye diameter
Lower eye diameter
Interorbital width (M)Interorbital width (F)Upper jaw length (O)Upper jaw length (B)Lower jaw length (O)Lower jaw length (B)Depth of caudal peduncle
Pectoral-fin length (O, M)
Pectoral-fin length (O, F)
Pectoral-fin length (B)Pelvic-fin length (O, M)
Pelvic-fin legnth (O, F)
Pelvic-fin length (B)Base length of pelvic-fin (O)Base length of pelvic-fin (B)Longest dorsal-fin ray
Longest anal-fin ray
Caudal-fin ray

Morphometric in SL:
Head length
Body depth

Number of type specimens
SL (mm)

81
62
11
9
6
6
3113
43
07
1025

2.33
2.72
8.15
1.81
1.72
1.17

1.81
2.3

2.33
2.3
1.85
1.83
2.26
1.48

4.66
3.08
3.02
7.76

3.61
1.94

E. kushimotoensis
1
58.9

77–88
59–65
11–13
8–9
6
6
2–311–122–3
38–42
078
102426

4.06–4.39
3.67–4.10
3.69–4.10
2.60–3.62
5.29
2.42–2.77
2.45–2.77
1.97–2.07
1.82–2.02
2.17–2.52
1.50–1.66
1.59
2.37–2.59
1.43–2.06
2.31
2.32–2.77
3.13–3.43
7.1–9.05
2.03–2.22
2.03–2.20
1.38–1.47

3.41–3.88
1.93–2.04

E. latifrons
5
52.8–78.4

84–89
64–69
10–11
9
6
6
310–113–4
45–51
0810102425

4.19–4.78
3.17–3.48
3.11–3.51
3.07–3.47
3.75–6.22
2.44–2.57
2.44–2.53
1.86–2.04
1.82–1.96
2.60–2.86
0.55–0.56
0.87–1.01
2.27–2.61
3.10–3.17
3.10–3.17
2.71–3.20
2.52–2.79
8.19–11.28
2.10–2.16
2.09–2.37
1.20–1.37

3.38–3.55
2.04–2.16

E. longipterum7
62.5–82.3

86–87
63–65
11–12
9
6–7
6
3113
42
06
1025

2.82
3.02
7.87–8.45
2.01
1.97
1.31–1.32

4.45–4.92
3.28–3.52
3.28–3.52
6.56
9.94
2.68–2.81
2.60–2.68
2–2.11
1.90–2.01
2.27–2.32
1.55
1.67
2.6
2.56

3.71–3.75
1.99–2.00

E. natalensis
2
44.2–62.7

87–96
67–76
11–14
7–10
6
6
2–311–132–3
42–46
079
102526

3.93–4.69
3.03–3.82
3.20–3.90
2.59–5.08
4.83–22.75
2.25–2.84
2.23–2.76
1.79–2.07
1.69–1.95
2.16–2.68
0.85–1.45
1.43–1.65
2.41–3.25
1.48–2.24
2.15–2.53
2.38–3.06
2.93–3.47
8.00–10.11
1.76–2.11
1.72–2.11
1.15–1.33

3.23–3.60
1.93–2.25

E. rostratum
33
31.0–72.0

83
62
12
9
6
6
3122
42
06
1025

2.5
3.27
8.89
2.16
2.16
1.26

2.32
1.98

2.67
2.67
2.03
1.95
2.5
1.16

4.57
3.56
3.64
3.72

3.56
2.22

E. sechellensis
1
56.9

80–89
60–68
11–13
7–10
7(6)
7(6)
2–311–132–3
40–45
0810102425

3.83–4.67
2.92–3.78
2.92–3.76
2.71–10.50
7.29–16.8
2.31–2.74
2.31–2.73
1.82–2.02
1.71–1.99
2.21–2.98
1.45–1.88
1.45–1.88
2.48–3.29
1.23–2.23
2.15–2.59
2.14–3.16
2.64–3.50
7.17–10.53
1.85–2.47
1.82–2.33
1.25–1.53

2.92–3.47
1.81–2.22

E. septempes
28
28.3–70.5

Table 1. Comparison of morphometric and meristic characters between E. kushimotoensis and related species. Highlighted features in Table are discriminative
characters between E. Kushimotoensis and the other species. All data based on type specimens. Mmale, Ffemale, Oocular side, Bblind side, HLhead length.
110
K. Amaoka, T. Kaga and H. Misaki

New Sinistral Flounder from Japan

Fig. 3. A scale (A) and first gill arch (B) fromocular side in Engyprosopon kushimotoensis
sp. nov. from the holotype, NSMT-P 76957,
male 58.9 mm SL. Scales indicate 0.5 mm(above) and 1 mm (below).

Kushimoto, Wakayama Prefecture.
Distribution. Known only from Kushimoto,
Wakayama Prefecture, Kii Peninsula.
Comparison. The new species is clearly amember of the genus Engyprosopon, having a divided caudal skeleton and showing sexual dimorphism in the rostral spine and body coloration on
the blind side (Amaoka, 1969; Amaoka et al.,
1993; Hensley and Amaoka, 2001). The present
description brings the number of recognizedspecies of the genus to 27, all known from watersof the Indo-Pacific Ocean (Fowler, 1934; Nor-111

man, 1934; Amaoka and Imamura, 1990; Hensley and Suzumoto, 1990; Quero and Golani,
1990; Amaoka et al., 1993; Amaoka and Mihara,
1995; Amaoka and Séret, 2005a, 2005b).
The new species is most similar to E. latifrons(Regan, 1908); E. longipterum Amaoka, Mihara
and Rivaton, 1993; E. natalensis (Regan, 1920);
E. rostratum Amaoka, Mihara and Rivaton, 1993;
E. sechellensis (Regan, 1908), and E. septempes
Amaoka, Mihara and Rivaton, 1993, in having
serrated gill rakers, a small number (fewer than10) of gill rakers on the lower limb of the firstgill arch, and in having uniserial teeth on theupper jaw (Table 1). It is easily separated fromthem, however, by the longer pectoral fin on theblind side (1.81 in head length vs more than 2.27
in these others), its narrower interorbital width(7.76 in head length vs 2.56–6.56, excepting for
2.71–10.50 in E. septempes), and many othercharacters as highlighted in Table 1.
In other ways, the new species resembles E.
rostratum and E. septempes in having a longer
upper jaw on the ocular side (2.33 in head lengthvs 2.25–2.84 and 2.31–2.74), a larger upper eye(3.08 in head length vs 3.03–3.82 and 2.92–3.78), and larger lower eye (3.02 vs 3.20–3.90
and 2.92–3.76), but it differs from E. rostratumin having a longer pelvic-fin base on the ocularside (2.72 vs 2.93–3.47), fewer dorsal and analfin rays (81 vs 87–96 and 62 vs 67–76), and anarrow interorbital width (7.76 vs 2.59–5.08)(Fig. 4). From E. septempes, E. kushimotoensis
differs in having a shorter head (3.61 in SL vs
2.92–3.47), fewer pelvic-fin rays (6 vs 7, rarely6), and gill rakers (07 vs 08–10), and a narrower interorbital width, when compared withmale E. septempes of about equal size (Fig. 4).
Key to Japanese Engyprosopon species. To
facilitate identifications of these similar species
we provide a key to the 7 species of Engyprosopon known from Japanese waters.

112

K. Amaoka, T. Kaga and H. Misaki

Fig. 4. Comparison of interorbital width in Engyprosopon kushimotoensis sp. nov., E. rostratum and E. septempes. , male (holotype) of E. kushimotoensis; , males and , females of E. rostratum; , male and , females of E. septempes.

Key to Species of Engyprosopon in Japanese Waters
1a. Distinct black blotch present at middle of upper- and lowermost rays of caudal fin . . . . . . . . . . . 2
1b. No black blotches present on caudal fin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2a. Gill rakers on lower limb13–18; some dark bands present at head margin anterior to interorbital
region; strong ctenoid scales along head margin; a black blotch on caudal fin between 3rd and6th rays counted from upper and lower margins of caudal fin, respectively . . . . . . . . . . E. xistrias
2b. Gill rakers on lower limb 6–8; no dark bands or strong ctenoid scales present on margin of head;a black blotch on caudal fin between 2nd or 3rd and 4th rays counted from upper and lower margins of caudal fin, respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3a. Body ovate, its depth more than 50% of SL; eye diameter longer than snout length; ocular side
pectoral fin in males not elongated, its length about equal to or less than head length; a black
blotch ranged between 3rd and 4th rays counted from upper and lower margins of caudal fin,respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. gandisquama
3b. Body rather elongate, its depth less than 50% of SL; eye diameter about equal to or less thansnout length; ocular side pectoral fin in males elongated and filamentous, usually with 2nd ray
longer than head length; a black blotch ranged between 2nd and 4th rays counted from upper andlower margins of caudal fin, respectively . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. multisquama
4a. Posterior margin of all gill rakers on first arch serrated; pelvic fin with elongate ray and distinct
black spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4b. Posterior margin of all gill rakers on first arch smooth; pelvic fin without elongate ray and distinct black spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

New Sinistral Flounder from Japan113

5a. Eye small, upper eye diameter 7–8% of SL; interorbital width wide, 6.4–8.5% of SL (50–66 mm
SL); upper jaw teeth in 2 rows; pelvic-fin ray in males elongated; males with pelvic-fin membrane with many black spots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. longipelvis
5b. Eye large, upper eye diameter 9% of SL; interorbital width narrow, 3.6% of SL (59 mm SL);
upper jaw teeth in 1 row; pelvic fin in males no elongated, no black spots on fin membrane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. kushimotoensis
6a. Upper jaw teeth in 2 rows; ocular-side pectoral fin elongate, usually longer than head length;
scales in lateral line 41–48 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. maldivensis
6b. Upper jaw teeth in 1 row; ocular-side pectoral fin not elongate, shorter than head length; scalesin lateral line 36–40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E. hureaui
Acknowledgments
We are grateful to T. W. Pietsch (UW) for
critically reading the manuscript, Kazuhiro
Nakaya, Mamoru Yabe and Hisashi Imamura(HUMZ) for valuable suggestions, Toshio Kawai(NSMT) for his assistance, and the staff of the
Marine Ecological Institute for related help withthis study.
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Manuscript received 30 May 2007; revised 21 November
2007; accepted 5 December 2007.
Associate editor: K. Matsuura.