Cypselurus angusticeps Nichols & Breder, 1935

Shakhovskoy, Ilia B. & Parin, Nikolay V., 2024, A review of the flying fish genus Cypselurus (Beloniformes: Exocoetidae). Part 3. Revision of the subgenus Cypselurus sensu stricto with descriptions of one new species and four new subspecies and reinstatement of Cypselurus crockeri Seale and Exocoetus socotranus Steindachner, Zootaxa 5473 (1), pp. 1-125 : 81-94

Cypselurus angusticeps Nichols & Breder, 1935

Synonymy and bibliography.

Cypselurus angusticeps Nichols & Breder, 1935: 2–3 , fig. 2 (original description; Tuamotu Arch.). Parin 1961a: 42–47, fig. 2 (description; Pacific Ocean). Parin 1961b: 103, 118, 129, 138, 140, 165, figs. 4b, 19g (morphology, systematics). Parin 1967: 52 (distribution). Kotthaus 1969: 12–13, figs. 163, 174 (description of a juvenile; off Mombassa). Masuda et al. 1975: 180 (short description; Ruykuy Is.). Yoshino et al. 1975: 71 (listed; Ryukyu Is.). Chen 1978: 291–294, 298–299 (osteology, distribution, identification key; Taiwan). Kovalevskaya 1980: 224 (listed). Kovalevskaya 1982: 110–112, figs. 4–5 (early life history stages; Indo-Pacific). Kovalevskaya 1983a: 1–2 (early life history stages). Parin 1984: EXOC Cyp 10–12 (comparison with other species of Cypselurus , figure, western Indian Ocean). Wass 1984: 8 (listed: Samoa). Heemstra & Parin 1986: 393 (in key; probable in South Africa). Chen 1987: 15, 19, 20, 26, 53, 54, 151, figs. 3-24, 4-8, 6-10, 6-20, Tabs. 2-1, 3-1, 4-8 (description, distribution, early life history stages; north-western Pacific). Chen 1988: 280–281, 283 (early life history stages; figures; distribution; Japan). Fedoryako 1989b: 567 (listed). Gillett & Ianelli 1991: 3 (listed; Niue, Tokelau). Chen 1993: 189–190 (short descriptions, figures; in part). Gillett & Ianelli 1993: 178 (listed; Pacific Islands). Lakshminaraina 1993: 29–30, fig. 4c (short description, distribution; «Indian Seas»). Abe 1994: 1278–1283, pls. 249–251 (description; Pacific Ocean). Parin 1996: 302, 306 [359, 363] (distribution; Pacific Ocean). Parin 1999: 2166, 2173 (distribution, diagnostic characters, figure; West-Central Pacific). Parin 2000: 600 (listed; South China Sea). Mundy 2005: 287 (listed; Hawaii). Paxton et al. 2006: 727 (listed; Australia). Fricke et al. 2011: 370 (listed; New Caledonia). Chang et al. 2012: 543 (Taiwan). Chang 2020: 8 (listed; Orchid I., Taiwan). Shakhovskoy & Collette 2022: 347, pl. 58 (short description, distribution; western Indian Ocean). Shakhovskoy & Parin 2022: 10, 88 (comparison with C. simus (Valenciennes) and C. nossibe ).

Cypsilurus angusticeps . Fowler 1949: 58 (description [after Nichols & Breder 1935]).

Cypselurus unicolor (non Valenciennes). Woods & Schultz 1953: 179, 183–186 (description, morphometry; Bikini and Eniwetok Atolls).

Cypselurus sp. juv. Parin 1960a: 256–257, fig. 18 (description of juveniles; north-western Pacific).

Cypselurus naresii (non Günther). Parin 1996: 302 [359] (distribution; in part: only Marquesas Islands).

Cypselurus heterurus (non Rafinesque). Elliott & Paredes 1996: 37, fig.12 (in part: only juvenile from fig. 12 [after Parin 1960a]).

See further synonymy and bibliography in the account for C. angusticeps folletti .

Probable misidentifications. White et al. (2013: 98, fig. 28.6) provided short description of C. angusticeps from Indonesia. But, judging by the photograph in the work (fig. 28.6), it was a misidentification.

Material examined. One hundred and eighty five specimens of C. angusticeps angusticeps 36.5–235 mm SL.

Polynesia. Full morphological study. IORAS 04422 (1, 220 mm SL), 6°58’S 154°00’W, 18.10.1961 . IORAS 04429 (1, 206 mm SL), 13°51’S 172°13’W, 6.02.1968 . IORAS 04431 (1, 196 mm SL), same data . IORAS 04433 (1, 153 mm SL), 14°18’S 153°08’W, 11.03.1968 . IORAS 04290 (1, 190 mm SL), 8°36’S 172°32’W, 5.12.1957 . IORAS 04298 (1, 226 mm SL), 4°57’S 172°36’W, 4.12.1957 . IORAS 04304 (1, 232 mm SL), 8°26’S 140°05’W, 26.09.1961 . IORAS 04147 (1, 214 mm SL), Manuae , 13.05.1965 . IORAS 04305 (1, 204.5 mm SL), Rarotonga , 5.06.1965 . IORAS 04306 (1, 194.5 mm SL), Manuae , 13.05.1965 . IORAS 04308 (1, 203 mm SL), Rarotonga , 5.06.1965 . IORAS 04309 (1, 203 mm SL), Rarotonga , 6.06.1965 . IORAS 04311 (1, 211.5 mm SL), Rarotonga , 5.06.1965 . IORAS 04149 (1, 126 mm SL), Manuae , 12.05.1965 . IORAS 04320 (1, 136 mm SL), 6°58’S 154°00’W, 17- 18.10.1961 . IORAS 04329 (1, 90.5 mm SL), 19°45’S 161°51’W, 28.02.1968 . SOSC Ref. No. 200 (1, 227 mm SL), Washington Is. , 2 mi offshore over a 10 ftm. bank, 9.06.1964 . ZMUC P341002 (1, 213 mm SL), 22.10.1928 . ZMUC P341003 (1, 207 mm SL), anchorage at Avarua, Rarotonga , 22.10.1928 . ZMUC P341005 (1, 189 mm SL), 14°13’S 173°13’W, 8.11.1928 .

Partial morphological study. AMNH 12984 * (holotype, 220 mm SL), Negonego I., Tuamotu Is., 5.11.1934 . AMNH 13295 * (paratypes) (3, 209– 228 mm SL), Tuamotus, Takakota , USNM 308455 * (2, 187– 197 mm SL), Niue, September 1989 . USNM 308457 * (2, 187– 201 mm SL), Tokelau, August 1989 . USNM 308459 * (1, 205 mm SL), Niue, September 1989 .

Hawaii. Full morphological study. IORAS 04307 (1, 235 mm SL), 23°19’N 158°20’W, 12.07.1965. IORAS 04339 (1, 95 mm SL), 18°31’N 175°00’W, 18.08.1970. USNM 179301 * (1, 207.5 mm SL) , Hawaii: Honolulu.

Partial morphological study. BPBM 34344 * (1, 223 mm SL), Townsend Cromwell 32-11, no data . BPBM 34380 * (1, 200 mm SL), Raita Bank , 29.09.1980 . USNM 052669 * (1, 197 mm SL), Hawaii : Puako Bay , 1901– 1902. USNM 92582 * (2, 206– 226 mm SL), Hawaii . USNM 179301 * (3, 209– 217 mm SL), Hawaii : Honolulu.

Western Pacific Ocean. Full morphological study. IORAS 04397 (1, 202 mm SL), 6°07’N 126°45’E, 4- 5.03.1966 . IORAS 04399 (1, 168.5 mm SL), 0°30’N 140°00’E, 17- 18.12.1975 . IORAS 04400 (1, 162.5 mm SL), 1°00’N 140°00’E, 19.12.1965 . IORAS 04404 (1, 203.5 mm SL), 8°22’N 137°57’E, 15.12.1965 . IORAS 04411 (1, 169.5 mm SL), 0°30’N 140°00’E, 17- 18.12.1965 . IORAS 04416 (1, 209 mm SL), 0°00’ 152°20’E, 31.12.1965 . IORAS 04287 (1, 221.5 mm SL), 2°56’N 172°42’E, 7- 8.02.1958 . IORAS 04288 (1, 209 mm SL), 11°23’N 142°12’E, 5.04.1958 . IORAS 04289 (1, 193 mm SL), 2°56’N 172°42’E, 7- 8.02.1958 . IORAS 04291 (1, 211 mm SL), 7°37’S 152°44’E, 22.03.1957 . IORAS 04292 (1, 197 mm SL), 6°16’S 153°44’E, 28- 29.07.1957 . IORAS 04293 (1, 166 mm SL), 5°49’S 152°53’E, 20- 21.07.1957 . IORAS 04294 (1, 177 mm SL), 8°38’N 141°57’E, 6.04.1958 . IORAS 04295 (1, 199 mm SL), 6°16’S 153°44’E, 28.07.1957 . IORAS 04296 (1, 192 mm SL), same data . IORAS 04297 (1, 179 mm SL), same data . IORAS 04299 (1, 200.5 mm SL), 7°51’N 134°56’E, 28.08.1957 . IORAS 04300 (1, 186.5 mm SL), 6°16’S 153°44’E, 28.07.1957 . IORAS 04301 (1, 170 mm SL), same data . IORAS 04302 (1, 170.5 mm SL), same data . IORAS 04303 (1, 180 mm SL), same data . IORAS 04177 (1, 205 mm SL), 5°00’N 126°56’E, 6.04.1961 . IORAS 04316 (2, 181 mm SL), 11°09’N 141°47’E, 26.04.1975 . IORAS 04317 (1, 187.5 mm SL), 11°22’N 142°51’E, 26- 27.04.1975 . IORAS 04437 (1, 140 mm SL), 8°22’N 137°58’E, 29- 30.03.1975 . IORAS 04321 (1, 124 mm SL), 9°08’N 153°53’E, 15.07.1957 . IORAS 04322 (3, 82–146 mm SL), 6°07’N 126°45’E, 4- 5.03.1966 . IORAS 04323 (1, 109.5 mm SL), 0°03’S 142°36’E, 22.12.1965 . IORAS 04324 (1, 141 mm SL), 6°20’N 122°36’E, 18.02.1973 . IORAS 04325 (1, 140 mm SL), ~ 7°N 135°31’E, 30.05.1971 . IORAS 04326 (1, 92 mm SL), 8°18’N 120°25’E, 1.07.1971 . IORAS 04327 (2, 70–84.5 mm SL), 10°24’N 126°40’E, 15- 16.02.1975 . IORAS 04328 (1, 81 mm SL), ~ 19°N 132°E, 8- 9.09.1985 . IORAS 04332 (1, 136 mm SL), 7°16’N 175°35’E, 27.11.1957 . IORAS 04334 (1, 117.5 mm SL), 13°53’N 147°01’E, 15.08.1957 . IORAS 04335 (2, 136– 143.5 mm SL), ~ 7°N 135°31’E, 3- 4.06.1971 . IORAS 04337 (2, 100.5– 125.5 mm SL), 10°21’N 126°34’E, 16- 17.02.1975 . IORAS 04338 (1, 87 mm SL), 23°05’N 143°14’E, 15.10.1955 . IORAS 04341 (3, 79–110 mm SL), 10°00’N 126°30’E, 1.03.1966 . IORAS 04342 (1, 112 mm SL), 6°16’S 153°44’E, 27- 28.07.1957 . IORAS 04344 (1, 52 mm SL), 11°15’N 141°42’E, 25- 26.04.1975 . IORAS 04345 (2, 75–78 mm SL), 3°22’N 127°20’E, 12.03.1966 . IORAS 04346 (1, 39 mm SL), 11°22’N 142°51’E, 26- 27.04.1975 . IORAS 04347 (1, 36.5 mm SL), ~ 10°N 142°E, 23.04.1975 . IORAS 04350 (1, 44 mm SL), 11°18’N 142°10’E, 19.08.1957 . IORAS 04351 (1, 94 mm SL), ~ 31°N 150°E, August 1954 . IORAS 04279 (1, 132 mm SL), 10°53’S 145°54’E, 17.01.1977 . CAS 81230 * (2, 175.5– 191 mm SL), 1°02’N 154°44’E, 22- 23.07.1954 . ZMUC 1415 (1, 168.5 mm SL), ~ New Britain Trench—Coral Sea . ZMUC P34919 (1, 174 mm SL), 2°08’N 125°21’E, 6.07.1929 .

Partial morphological study. IORAS 04318 (1, 129.5 mm SL), ~ 7°N 135°31’E, 3- 4.06.1971 . IORAS 04349 (1, 91.5 mm SL), 4°28’N 142°26’E, 1- 2.05.1971 . IORAS 04352 (1, 102 mm SL), ~ 7°N 135°31’E, 3- 4.06.1971 . IORAS 04353 (1, 128 mm SL), 7°51’N 134°56’E, 28.08.1957 . IORAS 04354 (1, 63 mm SL), 14°31’S 171°20’E, 1- 2.02.1958 . IORAS 04355 (1, 177 mm SL), 8°10’S 163°00’E, 4.06.1971 . IORAS uncat* (1, 172 mm SL), 4°28’N 142°26’E, May 1971 . IORAS uncat* (1, 52 mm SL), 4°59’S 125°56’E, 18.10.1959 . AMS IB.5521* (1, 179 mm SL), Ellice Islands . CAS 81844 * (1, 179 mm SL), 13°26’N 120°18’E, 21.01.1949 . CAS 82010 * (1, 147 mm SL), 3°N 126°E, 3.03.1948 . CAS 82159 * (1, 185 mm SL), 1°02’N 154°45’E, 2.07.1954 . SIO 61-562 * (1, 45 mm SL), 19°54’N 139°55’E, 16.05.1961 . URM P18176 * (1, 174 mm SL), Okinawa Fish Market . URM P18177 * (1, 179 mm SL), same place . URM P23742 * (1, 192 mm SL), same place . URM P23743 * (1, 181 mm SL), same place . URM P23901 * (1, 182 mm SL), same place . URM P25821 * (1, 215 mm SL), same place . USNM 140286 * (3, 190– 196 mm SL), Bikini Atoll, 6- 7.04.1946 . USNM 140292 * (5, 179– 210 mm SL), Eniwetok Atoll (leeward side of reef 2 miles south of Rigili I.), 24.05.1946 . USNM 167434 * (1, 231 mm SL), Gilbert Is., 7.07.1951 . USNM 40740812 (1, ~ 195 mm SL), Santa Ana Public Market, vendor claims captured near Palawig, Cagayan, 2.06.2012 .

Eastern Indian Ocean. Full morphological study. IORAS 04148 (1, 184.5 mm SL), 3°59’S 91°30’E, 4.09.1962 . IORAS 04310 (1, 224 mm SL), 7°17’S 105°07’E, 16.07.1962 . IORAS 04150 (1, 180 mm SL), 2°01’N 91°28’E, 11.09.1962 . IORAS 04152 (1, 212 mm SL), 16°03’S 90°05’E, 21- 22.12.1959 . IORAS 04153 (1, 190 mm SL), 9°22’N 92°43’E, 5.03.1961 . IORAS 04159 (1, 165 mm SL), 0°01’S 86°37’E, 9.01.1960 . IORAS 04160 (1, 187.5 mm SL), same data . IORAS 04162 (1, 194.5 mm SL), 8°10’S 104°39’E, 22- 23.03.1961 . IORAS 04164 (1, 178 mm SL), 9°22’N 92°43’E, 5.03.1961 . IORAS 04166 (1, 189 mm SL), 6°29’S 101°19’E, 20.11.1959 . IORAS 04170 (1, 206 mm SL), 10°24’S 105°39’E, 8- 9.11.1959 . IORAS 04172 (1, 193 mm SL), 7°48’N 95°11’E, 7.03.1961 . IORAS 04176 (1, 204.5 mm SL), 9°22’N 92°43’E, 5.03.1961 . IORAS 04178 (1, 198 mm SL), 5°37’N 94°46’E, 9.03.1961 . IORAS 04180 (1, 200 mm SL), 9°22’N 92°43’E, 5.03.1961 . IORAS 04181 (1, 194.5 mm SL), 8°10’S 104°39’E, 22- 23.03.1961 . IORAS 04184 (1, 178 mm SL), 9°22’N 92°43’E, 5.03.1961 . IORAS 04185 (1, 149 mm SL), 1°59’S 86°41’E, 11.01.1960 . IORAS 04193 (1, 183.5 mm SL), 9°22’N 92°43’E, 5.03.1961 . IORAS 04202 (1, 192.5 mm SL), Christmas I., 9.02.1965 . IORAS 04312 (1, 207 mm SL), same data . IORAS 04313 (1, 196 mm SL), same data . IORAS 04314 (1, 207 mm SL), same data . IORAS 04315 (1, 204 mm SL), same data . IORAS 04340 (2, 102– 109 mm SL), 15°53’S 102°28’E, 26.11.1959 . IORAS 04319 (1, 123 mm SL), 10°46’S 113°31’E, 26.10.1959 .

Partial morphological study. IORAS 04348 (1, 86 mm SL), 9°24’S 114°06’E, 25.10.1959 . IORAS uncat* (1, 43.5 mm SL), 9°15’N 94°23’E, 6.03.1961 . IORAS uncat* (2, 63–198 mm SL), 5°06’N 91°32’E, September 1962 . FRSKU 112133 * (1, 199 mm SL), 23°03’S 113°09’E, 14.12.1988 . FRSKU 112135 * (1, 227 mm SL), same data . FRSKU 112653 * (1, 210 mm SL), 32°00’S 114°47’E, 22.12.1987 . FRSKU 113934 * (1, 184 mm SL), off North West Cape , Australia, November 1989 . SIO 61-720 * (1, 199 mm SL), 11°11’S 122°29’E, 29.03.1961 . WAM 29667 *(?) (5, 188– 210 mm SL), 20°29’S 114°53’E, 11.01.1988 .

Western Indian Ocean. Full morphological study. IORAS 04392 (1, 191 mm SL), ~ 19°22’S 61°31’E, 24.04.1983 . IORAS 04163 (1, 212.5 mm SL), 11°42’S 49°11’E, 7.03.1960 . IORAS 04189 (1, 200 mm SL), 2°46’S 65°41’E, 13.02.1960 . IORAS 04203 (1, 213 mm SL), 13°27’S 54°53’E, 16- 17.12.1964 . IORAS 04330 (1, 66 mm SL), 2°03’N 54°28’E, 12.03.1974 . IORAS 04331 (1, 134.5 mm SL), 9°17’N 71°00’E, 9.12.1960 . IORAS 04333 (1, 118 mm SL), 9°27’S 53°28’E, 4.03.1960 . IORAS 04336 (1, 118 mm SL), 8°51’S 41°52’E, 13.03.1960 . IORAS 04343 (1, 134 mm SL), 5°11’S 52°09’E, 9.05.1967 . SOSC Acc. No. 44 (1, 180 mm SL), 5°S 60°E, 23.08.1963 . SOSC Ref. No. 170 (1, 41 mm SL), 11°25’S 44°25’E, 31.10.1964 .

Partial morphological study. IORAS uncat* (1, 54 mm SL), 1°03’S 76°18’E, 23.01.1960 . IORAS uncat* (1, 55 mm SL), 1°07’N 54°32’E, 15.03.1983 . SAIAB uncat (1, 200 mm SL), Comoros 13 . SIO 63-663 * (1, 65 mm SL), 0°03’S 76°56’E, 10.07.1962 .

Additional material is listed below in the account for C. angusticeps folletti .

The holotype and paratypes of C. angusticeps were studied by the second author. The data for the holotype are given below.

Holotype. AMNH 12984 , Templeton Crocker , Tuamotu Islands , Negonego Island , captured on 5 November 1934. Length 220 mm SL. D 13, A 9, P I 14, Spred 27, Str 7, Sp.br 21 (6 + 15), Vert 41 (26 + 15). Measurements (in % SL): cV 1 36.7, pV 37.6, c 24.5, o 8.1, io 1 8.1, H 19.7, h 7.0, Dc 30.0, lP 69.2, lP1 39.6, lV 27.2, HD 10.0, p

12 This specimen was studied by the first author basing only on photographs on USNM website and X-rays [by the courtesy of K.E. Bemis ( USNM)].

13 This specimen was studied by the first author basing only on photograph [by the courtesy of E. Heemstra ( SAIAB)].

13.2. Pectoral fins brown to 8th ray, pectoral-fin tip slightly protruding beyond the end of dorsal-fin base. Pelvic fins pale, pelvic-fin tip reaching 6th ray of anal fin. First anal-fin ray beneath 6th dorsal-fin ray. Photo and X-rays of the holotype are available on the AMNH website14 .

Diagnosis. A large species of Cypselurus with many dorsal-fin rays and few predorsal scales and vertebrae. Body rather deep, head and eyes large, pectoral, pelvic and dorsal fins long. Pelvic-fin base slightly closer to posterior edge of head than to origin of caudal-fin lower lobe or about midway. Jaw teeth with additional cusps, conical and tricuspid, palatine teeth absent or very few in number. Juveniles with a rather short, necktie-like chin barbel and low dorsal fin; ventral side of their body paler than dorsal one. In adults, pelvic and anal fins usually pale. D 11–15, Spred 23–31, Str 7–9½, Vert 39–42 (25–29 + 13–16).

Description. Meristic and morphometric characters are given in Tables 1–7, 12 and 14. D 11 –15 (usually 12–14), A 7–10 (usually 8–9), P I 12–16 (usually I 13–14), Spred 23–31 (usually 25–28), Str 7–9½ (usually 7½–8), Sp.br 20–26 (4–8 + 14–18), usually 21–24 (6–7 + 15–17), Vert 39–42 (25–29 + 13–16), usually 40–42 (26–27 + 14– 15). Snout moderate ( Figs. 37 , 38 ), lower jaw usually shorter than upper jaw, sometimes jaws of equal size (in fish <150 mm SL lower jaw usually a bit longer or jaws equal). Upper jaw not pointed anteriorly ( Figs. 37 , 38 ). Juveniles <155 mm SL with a rather short, necktie-like chin barbel ( Fig. 39 ) reaching from eye rear margin to slightly beyond pectoral-fin base (length of barbel slightly decreasing with growth, see Fig. 40 ). Chin barbel widened distally (occasionally rather narrow) and usually tapered terminally; it has a weak median keel proximally (in a few fish the keel reaches tip of barbel) but without triangular lobes basally. Jaw teeth not numerous, small to medium-sized (not visible or barely visible to naked eyes), with additional cusps, conical and tricuspid (usually all three types present, sometimes only one or two); juveniles <80 mm SL usually with conical teeth only. Teeth arranged in 1–3 rows. Palatine teeth absent or very few in number (only 65 of 156 specimens studied had palatine teeth).

Body rather deep, its depth not changing with growth, 4.6–6.0 in SL. Body width 1.07–1.55 and caudal peduncle depth 2.30–3.12 in greatest body depth. Greatest head depth and head length change little with growth ( Fig. 40 ), Hc 5.0– 6.2 in SL and c 4.4– 3.5 in SL and 1.00– 1.28 in dorso-caudal distance. Eyes large, their diameter decreasing with growth ( Fig. 40 ): in juveniles 35–140 mm SL eye 8.3–13.5 in SL, 2.35–3.3 in head length, 0.7–1.2 in interorbital width and 1.05–1.5 in postorbital distance; in fish 140–235 mm SL, 10.5–14.9 in SL, 3.0– 3.6 in с, 0.95–1.35 in io and 1.1–1.6 in po. Snout length barely increasing with growth.

Pectoral fins long, their length nearly constant with growth to about 140 mm SL, and afterwards slightly decreasing ( Fig. 4c ): in juveniles 35–140 mm SL pectoral fin 1.3–1.45 in SL and in fish 140–235 mm SL, 1.35–1.6 in SL. Tip of pectoral fin reaching from end of dorsal-fin base to origin of caudal-fin upper lobe (in juveniles sometimes slightly beyond). First pectoral-fin ray unbranched, its length slightly decreasing with growth ( Fig. 4d ): in juveniles 35–140 mm SL 2.2–2.5 in SL and 1.56–1.86 in lP; in fish 140–235 mm SL, 2.15–2.8 in SL and 1.46– 1.92 in lP. Pelvic-fin base slightly closer to posterior edge of head than to origin of caudal-fin lower lobe or about midway (cV / pV = 0.79–1.06, see Fig. 4a ). Pelvic-fin length decreasing strongly with growth: in juveniles 35–140 mm SL pelvic fin 2.4–2.9 in SL and 1.70–2.08 in lP; in fish 140–235 mm SL, 2.7–3.9 in SL and 1.90–2.60 in lP. Tip of pelvic fin in juveniles 35–130 mm SL reaching origin of caudal-fin lower lobe or protruding beyond; in fish 130–160 mm SL from middle of caudal peduncle to origin of caudal-fin lower lobe (sometimes slightly beyond); in fish 160–190 mm SL from end of anal-fin base (or nearly so) to middle of caudal peduncle and in fish> 190 mm SL from middle to end of anal-fin base.

Anal-fin origin far posterior to dorsal-fin origin (1st anal-fin ray under 5th–8th dorsal-fin ray, usually under 6th–7th). Dorsal fin with 2–6 (usually 3–5) rays more than anal fin. Height of dorsal ( Fig. 4e ) and anal fins decreasing with growth: in juveniles 35–140 mm SL HD 6.65–8.5 in SL and HA 8.1–13.3 in SL; in fish 140–235 mm SL, HD 8.2–10.6 in SL and HA 11.75–16.95 in SL. Longest dorsal- and anal-fin ray—2nd or 3rd (occasionally 4th in dorsal fin and 1st in anal fin). In juveniles 35–80 mm SL tip of last dorsal-fin ray reaching (nearly reaching) origin of caudal-fin upper lobe or protruding slightly beyond; in fish> 80 mm SL it protrudes beyond the middle of caudal peduncle but usually does not reach origin of caudal-fin upper lobe. Middle and posterior rays of dorsal fin not elongated ( Figs. 37 , 38 ), in juveniles <120 mm SL tip of penultimate ray only slightly extending beyond tip of last ray (rarely at the same level), in larger fish tip of penultimate ray always ahead of last ray’s tip.

Pigmentation. Body of juveniles and adults with typical “pelagic” pigmentation, dark body bands always absent ( Fig. 38 ). Like in C. naresii and C. hiraii , some juveniles of C. angusticeps 35–100 mm SL have a wide brown longitudinal stripe through the eye ( Fig. 38 ). Ventral surface of head in juveniles 35–150 mm SL pale with brown

14 https://emu-prod.amnh.org/db/emuwebamnh/Display.php?i=0

(eastern Pacific)

C. a. angusticeps (Polynesia)

C. a. angusticeps (Hawaii)

C. a. angusticeps (western Pacific)

C. a. angusticeps (E Indian Ocean)

C. a. angusticeps (W Indian Ocean) a

C. a. angusticeps (all regions) 78.3 69.8 59.9 35.0 36.1 38.0 25.2 11.0 8.0 5.3 7.5 9.0 182.5

153 (n=103) (n=101) (n=101) (n=102) (n=50) (n=152) (n=146) (n=103) (n=124) (n=94) (n=4) (n=95) 100.5–235.0

76.3–80.9 67.3–72.3 58.1–61.9 32.8–38.1 32.6–39.5 34.4–40.3 23.3–27.6 10.1–12.9 6.9–9.5 4.6–6.2 7.0–7.7 8.0–10.0 ......continued on the next page (eastern

198.9 122.0–225.0 - 17.0 (n=32) 16.2–18.0 18.6 (n=28) 17.6–20.6 6.9 (n=31) 6.3–7.5 28.1 25.5–30.0 69.5 (n=29) 65.2–75.0 42.0 (n=31) 39.0–46.3 28.5 (n=31) 25.7–36.8 19.8 (n=32) 18.1–22.0 10.9 (n=32) 9.6–12.3 10.4 (n=18) 10.0–12.0 7.0 (n=23) 6.2–9.2 13.5 (n=32) 12.5–14.4 11.4 (n=1) 70.4 36.5–94.0 - 18.4 (n=14) 17.5–19.3 19.1 (n=15) 18.1–20.8 7.7 (n=15) 7.2–8.2 29.0 (n=17) 27.6–29.9 72.4 (n=16) 69.4–76.1 43.0 (n=17) 40.6–45.6 40.0 (n=12) 38.5–41.6 21.2 (n=15) 19.5–22.7 11.9 (n=15) 10.8– 12.9 14.0 (n=7) 13.0–15.0 10.6 (n=12) 9.3–12.3 16.0 (n=15) 15.1–17.4 26.1 (n=16) 21.7–35.8 170.5 100.5–231.0 8.5 (n=11) 7.7–9.6 17.9 (n=43) 16.5–19.4 19.2 (n=51) 17.2–21.5 7.3 (n=50) 6.4–8.0 28.5 (n=68) 26.5–30.2 69.9 (n=38) 65.6–75.0 41.4 (n=42) 35.5–45.6 32.8 (n=44) 27.8–40.7 20.6 (n=46) 18.3–22.6 11.0 (n=47) 9.3–12.4 11.8 (n=24) 10.5–13.7 7.8 (n=24) 5.9–9.0 14.1 (n=49) 12.5–16.2 20.3 (n=16) 12.2–25.8 64.7 43.5–86.0 - - - - 29.9 28.5–31.3 74.3 (n=1) 41.2 (n=1) 41.6 (n=1) - - 13.4 (n=1) 9.6 (n=1) - 21.7 (n=2) 20.0–23.4

Pacific)

C. a. angusticeps

(western Pacific)

C. a. angusticeps pigmentation of varying intensity only on chin. A few small dark specks may be present on gill cover (sometimes also under eye) of some adults, but the specks probably covered with iridocytes in life.

Chin barbel ( Figs. 37a–b , 39 ) of juveniles pale with pale brown to dark brown base or, in larger juveniles, proximal one-third of barbel, and a wide dark brown to black subterminal band (some fish also with pigmentation along barbel’s lateral edges). Pigmentation of median keel usually matches the barbel’s pigmentation. Opposite (ventral) side of barbel pigmented similarly ( Fig. 37b ).

Pectoral fins in juveniles and adults ( Figs. 37a,c ; 41a–c ) gray to dark brown to 7th–9th (rarely 10th) ray with a pale tip and, in adults, a narrow pale posterior edging. In adults, pectoral fins frequently with violet tinge, and sometimes pigmentation faded proximally.

Pelvic fins of juveniles 35–145 mm SL pale brown to dark brown (pigmentation usually slightly paler proximally and, in larger juveniles, along 1st and 6th rays), usually with a pale area near tip of 3rd (sometimes also 2nd) ray ( Fig. 41d–e ). In fish> 145 mm SL pigmentation starts to disappear proximally and along 1st and 6th rays, and in fish> 165 mm SL pelvic fins pale, sometimes with a weak grayish to pale brown pigmentation distally between 3rd–5th rays ( Fig. 41f–h ). However, in few adults (hybrids with C. naresii ?) pelvic fins with a distinct large brown spot distally.

Dorsal fin of juveniles 35–150 mm SL pale brown (usually darker in the upper part) ( Fig. 38a–e ). In fish> 150 mm SL dorsal fin gray to pale-brownish (in fish 150–195 mm SL usually with darker upper margin).

Anal fin of juveniles 35–150 mm SL mainly pale in the anterior part and along fin base, and more or less densely covered with melanophores in the posterior part (in some fish anal fin much darker—nearly covered with melanophores except a paler base and distal portion of anterior rays). In fish> 160 mm SL anal fin translucent or grayish (in few fish single dots persist in the lower part of anal fin).

Caudal fin of juveniles 35–110 mm SL ( Fig. 38a–d ) pale with pale brown to brown base and brown dotted pigmentation along lower lobe rays (except uppermost rays) and, in some fish, also with sparser pigmentation along upper rays of upper lobe. Dark bands usually absent on both lobes, but in some fish tip of lower lobe can be slightly darker or a faint band present. In fish> 110 mm SL ( Fig. 38e–f ) caudal fin pale brown to brown, sometimes with darker fin base and tip of upper lobe.

Coloration in life. According to Masuda et al. (1975), coloration of pectoral fins of C. angusticeps is dusky pale-reddish. Chen (1987) reported that pale red coloration appears on pectoral fins of adults during spawning. According to Abe (1994), pectoral fins of C. angusticeps are pink-brownish to 6th–8th ray, pelvic fins transparent, only the rays being greyish, dorsal fin greyish, anal fin transparent and caudal fin greyish.

Maximum size. The maximum length of C. angusticeps in the material examined was 235 mm SL (IORAS 04307, close to mature female). The largest male was 225 mm SL (IORAS 04438).

Intraspecific variation. Fish from the eastern Pacific differ in number of predorsal and transverse scales, head length, eye diameter and body proportions of juveniles (see Tables 2–3, Fig. 40 ), and we consider these differences as sufficient for separating them as a subspecies— C. a. folletti (see below). Samples of C. a. angusticeps differ slightly in some counts and measurements (see Tables 1–7, 10, 12, 14; Fig. 40 ), but we regard these differences as not having taxonomic significance.

Comparative remarks. Cypselurus angusticeps differs from C. hiraii in fewer vertebrae, transverse and predorsal scales, and gill rakers (see Tables 2–6), a longer head (22.8–28.4, usually> 24.0 vs. 21.2–24.7, usually <24.0% SL), larger eye (in fish ≥ 150 mm SL eye diameter 6.7–9.5, usually> 7.0 vs. 6.0–6.9% SL), deeper body, head and caudal peduncle (H 16.7–21.7, usually> 18.0 vs. 13.9–19.4, usually <18.0; Hc 16.1–20.0, usually> 17.0 vs. 13.9–16.8 % SL; in fish ≥ 150 mm SL, h 6.3–7.8, usually> 6.5 vs. 5.5–6.9, usually <6.5% SL), as well as in length and morphology of chin barbel ( Figs. 2 , 4f , 39 ), caudal-fin pigmentation in juveniles and some other characters (see Table 7).

Cypselurus angusticeps differs from C. opisthopus in fewer vertebrae and predorsal scales and more dorsal-fin rays ( Tables 1, 3, 6), more anterior position of pelvic-fin base (aV 57.5–62.1, usually <61.5 vs. 60.7–67.0, usually> 62.0% SL; index cV/pV 0.79–1.06 vs. 1.04–1.46, usually> 1.10, see Fig. 4a ), longer dorsal fin originating more anteriorly [lD 18.1–24.1, usually> 19.0 vs. 15.0–20.0, usually <19.0% SL; aD 67.2–72.3, usually <71.5 vs. 70.5–77.2, usually> 71.5% SL; Dc 25.5–31.3, usually> 27.0 vs. 23.0–27.5, usually <27.0% SL ( Fig. 4a )], longer pectoral fins ( Fig. 4c–d ) and other characters (see Table 7). Juveniles also differ in chin barbel length and morphology ( Figs. 4f , 12 , 39 ), pigmentation of body and fins (see descriptions above), deeper body, larger and deeper head, longer snout, narrower interorbital space, and lower dorsal fin (see Table 7, Fig. 4d ). Adults also differ in palatine teeth (absent or few in number vs. present, usually numerous), head pigmentation (dark specks absent or few in number vs. present, usually numerous) and larger maximal size (235 vs. 186 mm SL).

Cypselurus angusticeps differs from C. persimilis in more dorsal-fin rays ( Table 1), more anterior position of pelvic-fin base (aV 57.5–62.1, usually <61.5 vs. 61.8–66.4% SL; index cV/pV 0.79–1.06, usually <1.00 vs. 0.97–1.24, usually> 1.00, see Fig. 4a ), longer dorsal fin originating more anteriorly [lD 18.1–24.1 vs. 14.3–17.7% SL; aD 67.2–72.3 vs. 72.3–75.9% SL; Dc 25.5–31.3 vs. 21.8–25.5% SL ( Fig. 4b )], longer pectoral fins ( Fig. 4c ), as well as in head pigmentation (dark specks absent or few in number vs. present, usually numerous), palatine teeth (absent or sparce vs. usually present, numerous), larger maximum size (235 vs. 180.5 mm SL) and other characters (see Table 7).

The main identification challenge is to distinguish adults of C. angusticeps from C. naresii and C. nossibe . Cypselurus angusticeps differs from C. naresii in more dorsal-fin rays [11–15, usually ≥ 13 vs. 9–13, usually ≤ 12 (except C. n. septentrionalis)], fewer predorsal scales (23–31, usually ≤ 28 vs. 26–37, usually ≥ 28) and vertebrae [39–42, usually ≤ 41 vs. 40–45, usually ≥ 42 (except C. n. socotranus )], longer dorsal fin originating more anteriorly (lD 18.1–24.1, usually> 19.0, aD 67.2–72.3, usually <71.0, Dc 25.5–31.3, usually> 27.0% SL in C. angusticeps vs. lD 14.0–20.0, usually <19.0, aD 68.8–75.7, usually> 71.0, Dc 22.0–27.5, usually <27.0% SL in C. naresii ), more anterior position of pelvic-fin base (index cV/pV 0.79–1.06, usually <1.00 vs. 0.91–1.22, usually> 1.00 (except C. n. septentrionalis), see Fig. 4a ), palatine teeth (usually absent vs. usually present) and some other characters (see Tables 1, 7). Additionally, juveniles of C. angusticeps differ from C. naresii in chin barbel length and morphology ( Figs. 4f , 22 , 26 , 39 ), a longer and deeper head, larger eye and deeper body ( Table 7), longer pectoral fins ( Fig. 4c ), higher dorsal fin ( Fig. 4e ), as well as in pigmentation of the body and caudal fin (see descriptions above); adults in pelvic-fin pigmentation (usually pale vs. usually pigmented distally).

Cypselurus angusticeps is also very similar to C. nossibe in the adult stage. Cypselurus angusticeps has slightly more dorsal-fin rays (11–15, usually ≥ 13 vs. 11–13, usually ≤ 12), fewer transverse scales (7–9½, usually ≤ 8 vs. 8–9, usually ≥ 8½) and vertebrae (39–42, usually ≤ 41 vs. 41–43, usually ≥ 42), and a narrower body width (in juveniles 35–125 mm SL, 12.9–17.4 vs. 15.6–19.0% SL; in adults, 12.2–15.7, usually <14.5 vs. 14.8–15.8% SL). Adults also differ in teeth morphology (palatine teeth absent or sparse, jaw teeth mainly conical and with additional cusps in C. angusticeps vs. palatine teeth numerous, jaw teeth mainly tricuspid in C. nossibe ), head pigmentation (dark specks absent or few in number vs. usually numerous), longer dorsal (18.1–22.6, usually> 19.5 vs. 18.0– 19.2% SL) and anal (9.1–12.4, usually> 9.5 vs. 8.0–10.9, usually <9.5% SL) fins, as well as larger maximum size (235 vs. 183 mm SL). Juveniles 35–125 mm SL also differ in chin barbel morphology (long and wide, pale with two dark zones in C. angusticeps vs. absent or diminutive and entirely dark in C. nossibe ), pigmentation of body, pectoral and caudal fins (see description of C. nossibe in Shakhovskoy & Parin 2022), longer snout (4.0–5.8, usually> 4.5 vs. 2.3–4.8, usually <4.5% SL), narrower interorbital width (7.8–10.0 vs. 10.2–12.7% SL) and longer pectoral fins (lP 69.4–76.1 vs. 59.0–71.2, usually <68.0% SL; lP1 39.7–45.6 usually> 41.0 vs. 31.5–41.0).

From all species of the subgenus Poecilocypselurus , C. angusticeps differs in presence of a chin barbel in juveniles and in the tooth morphology of adults (palatine teeth absent or sparse, jaw teeth mainly conical and with additional cusps vs. palatine teeth present and usually numerous, jaw teeth usually tricuspid [except C. bosha and C. olpar ]). Cypselurus angusticeps also differs from C. poecilopterus (Valenciennes) , C. simus and C. callopterus in pectoral-fin pigmentation (without spots vs. spotted15), from C. bosha and C. olpar in fewer anal-fin rays and vertebrae, longer pelvic fins and pigmentation of pectoral fins (see Shakhovskoy & Parin 2019) and from C. starksi Abe , C. oligolepis , C. neglectus , C. clariangulatus Shakhovskoy & Parin and C. izumii Shakhovskoy & Parin in fewer transverse scales and more posterior position of the pelvic-fin base (except C. neglectus ), as well as from C. starksi and C. izumii in fewer vertebrae (from C. izumii also in shorter pelvic fins and slimmer caudal peduncle) and from C. neglectus in longer dorso-caudal distance (see Shakhovskoy & Parin 2022).

Biology. Females and males are mature by 200 and 195 mm SL, respectively. Mature and close to mature adults were captured in February ( IORAS 04315 , Christmas I.), March ( IORAS 04176 & 04180, 9°22’N 92°43’E; IORAS 04172 , 7°48’N 95°11’E; IORAS 04397 , 6°07’N 126°45’E), April ( IORAS 04177 , 5°00’N 126°56’E), May ( IORAS 04438 , Socorro I.; USNM 140292 , Eniwetok Atoll), June ( SOSC Ref. No. 200, Washington Is.), July ( IORAS 04307 , 23°19’N 158°20’W; USNM 167434 , Gilbert Is.) and August ( SIO 64-695 , Socorro I.). According to Chen (1987), small juveniles 10–25 mm SL were captured between 22– 25°N 125– 130°E in May–June. Thus, spawning season of C. angusticeps in the eastern Indian Ocean and in the Pacific is protracted at least from February to August , but probably with some time lag eastwards .

Distribution. Distribution of C. angusticeps and its subspecies based on our data is shown in Figure 42 . This neritic species is distributed in the Indo-Pacific, mainly in waters off oceanic islands, from East Africa (ZMH 4980, 63.5 mm SL, 4°42’S 41°22’E) to Mexico (LACM W-56-140-1, 16°05’N 102°55’W) and from about 31°N 150°E (IORAS 04351) to south-western Australia (FRSKU 112653, 32°00’S 114°47’E). Also, Chen (1978), Chang et al. (2012) and Chang (2020) reported this species from the waters of Taiwan, Fricke et al. (2011) listed it for New Caledonia, and Kovalevskaya (1982) reported larvae and juveniles from Gulf of Aden, off north-western coast of India and off north-eastern Madagascar.

Cypselurus angusticeps is rare in internal Indonesian seas and, like C. opisthopus , C. naresii and C. persimilis , seems to avoid waters over wide continental shelves. Two subspecies of C. angusticeps are isolated by oligotrophic wastes of open ocean about 20° wide, but C. a. folletti seems to be connected with the nominate through its Hawaiian population, as the sample from there is somewhat intermediate in counts of predorsal and transverse scales ( Tables 2–3).

15 Cypselurus simus occasionally lacks pectoral fin spots, and such specimens are very hard to distinguish from C. angusticeps . Number of vertebrae, interorbital width, caudal peduncle depth and body width should be taken into account in such a case (see Shakhovskoy & Parin 2010).

Figures

FIGURE 2. Chin barbel of Cypselurus hiraii (ventral view of head). (A)—47 mm SL, IORAS 04133, 41°35–58’N 138°28’E; (B)—50 mm SL, IORAS 04132, 41°31’N 142°17’E; (C)—52 mm SL, IORAS 04132, same place; (D)—61.5 mm SL, IORAS 04127, 37°N 160°E; (E)—71 mm SL, IORAS 04133, 41°35–58’N 138°28’E

FIGURE 4. Size variation of morphometric characters (in % SL) in Cypselurus hiraii (◊), C. opisthopus (∆), C. naresii (○), C. persimilis (+), C. angusticeps (□) and C. comatus (x): (A)—cephalo-ventral distance divided by postventral distance (index cV/ pV); (B)—dorso-caudal distance (Dc); (C)—pectoral-fin length (lP); (D)—length of the first pectoral-fin ray (lP1); (E)—height of dorsal fin (HD); (F)—length of chin barbel (Lcir).

FIGURE 12. Chin barbel of Cypselurus opisthopus opisthopus (ventral view of head). (A)—19 mm SL, AMS uncat., Madang; (B)—57 mm SL, IORAS 04088, 0°39’–0°04’S 148°13’–148°20’E; (C)—72 mm SL, IORAS 04105, ~ 1°S 143°E; (D)—72 mm SL, IORAS 04105, same place; (E)—82 mm SL, IORAS 04086, 5°38’S 147°04’E.

FIGURE 22. Chin barbel of Cypselurus naresii ordinarius (A–C) and C. n. albitaenia (D–F) (ventral view of head). (A)—51.5 mm SL, IORAS 04222, 10°48’S 104°38’E; (B)—78 mm SL, IORAS 04223, 6°20’N 122°36’E; (C)—121 mm SL, IORAS 04244, 5°38’S 147°04’E; (D)—53 mm SL, IORAS 04224, 4°30’S 75°00’E; (E)—86 mm SL, IORAS 04247, 7°10’S 67°39’E; (F)—168 mm SL, IORAS 04211, 6°44’S 59°16’E.

FIGURE 26. Holotype of Cypselurus naresii septentrionalis, 44 mm SL, ZMMU P-24608, 29°51’N 131°10’E. (A)—side view; (B)—ventral view.

FIGURE 37. Cypselurus angusticeps angusticeps. (A)—87 mm SL, IORAS 04338, 23°05’N 143°14’E (after Parin 1960); (B)—same specimen, close up of ventral side of chin barbel (after Parin 1960); (C)—226 mm SL, IORAS 04298, 4°57’S 172°36’W (after Parin 1961a).

FIGURE 38. Cypselurus angusticeps angusticeps. (A)—39 mm SL, IORAS 04346, 11°22’N 142°51’E; (B)—52 mm SL, IORAS 04344, 11°15’N 141°42’E; (C)—92 mm SL, IORAS 04326, 8°18’N 120°25’E; (D)—109 mm SL, IORAS 04340, 15°53’S 102°28’E; (E)—134.5 mm SL, IORAS 04331, 9°17’N 71°00’E; (F)—227 mm SL, SOSC Ref. No. 200, Washington Is.

FIGURE 39. Chin barbel of Cypselurus angusticeps angusticeps (ventral view of head). (A)—36.5 mm SL, IORAS 04347, ~ 10°N 142°E; (B)—66 mm SL, IORAS 04330, 2°03’N 54°28’E; (C)—93 mm SL, IORAS 04341, 10°00’N 126°30’E; (D)—109 mm SL, IORAS 04340, 15°53’S 102°28’E; (E)—136 mm SL, IORAS 04320, 6°58’S 154°00’W; (F)—143.5 mm SL, IORAS 04335, ~ 7°N 135°31’E.

FIGURE 40. Size variation of morphometric characters (in % SL) in Cypselurus angusticeps angusticeps (blue square— Polynesia, orange square—Hawaii, black square—western Pacific Ocean, lilac triangle—eastern Indian Ocean, green triangle— western Indian Ocean) and C. a. folletti (●). (A)—head length (c); (B) –postorbital distance (po); (C)—eye diameter (o); (D)—head depth (Hc); (E)—body width (p); (F)—length of chin barbel (Lcir).

FIGURE 41. Pectoral (A–C) and pelvic (D–H) fins of Cypselurus angusticeps angusticeps. (A & D)—52 mm SL, IORAS 04344, 11°15’N 141°42’E; (B)—92 mm SL, IORAS 04326, 8°18’N 120°25’E; (C)—123 mm SL, IORAS 04319, 10°46’S 113°31’E; (E)—140 mm SL, IORAS 04325, ~ 7°N 135°31’E; (F)—177 mm SL, IORAS 04355, 8°10’S 163°00’E; (G)—178 mm SL, IORAS 04164, 9°22’N 92°43’E; (H)—227 mm SL, SOSC Ref. No. 200, Washington Is.

FIGURE 42. Distribution of Cypselurus angusticeps angusticeps (○) and C. a. folletti (◊). Filled symbols indicate capture location for fishes ≤ 100 mm SL, open symbols indicate capture location for fishes> 100 mm SL; holotype position marked with asterisk.