Henicorhynchus entmema ( Fowler, 1934 )

Ciccotto, Patrick J. & Page, Lawrence M., 2020, Revision of the Genus Henicorhynchus, with a Revised Diagnosis of Gymnostomus (Cyprinidae: Labeoninae), Copeia 108 (3), pp. 485-502 : 485-502

Henicorhynchus entmema ( Fowler, 1934)

Notched Mud Carp

Figure 5

Tylognathus entmema Fowler, 1934:134 , figs. 101–102. Type locality: Thailand: Bangkok: Silom canal. Holotype: ANSP 59092 .

Cirrhina sauvagei Fang, 1942:168 . Type locality: Mekong , southeastern Asia. Syntypes: MNHN 8598 [8].

Crossocheilus thai Fowler, 1944: 49 , 1 fig. Type locality: Thailand, Bangkok. Holotype: ANSP 71336 .

Henicorhynchus lobatus Smith, 1945:257 , fig. 49. Type locality: Thailand: Chiang Rai Province: Mekok River near Chiang Rai. Holotype: USNM 119490 .

Cirrhinus lobatus — Roberts, 1997.

Gymnostomus lobatus — Kottelat, 2013.

Diagnosis.— A member of Henicorhynchus distinguished from other members of the genus ( Table 1) by the following combination of characters: mouth subterminal, weakly oblique to nearly horizontal (less than or equal to 208 to midline of body); maxillary barbels almost always present (rarely absent); edge of rostral cap with distinct medial indent; flank immaculate, without longitudinal stripes; caudal peduncle immaculate or with brown to black spot at medial insertion of caudal fin; caudal fin mostly clear, with scattered melanophores; pectoral, pelvic, and anal fins hyaline in life.

Comparisons.— Henicorhynchus entmema is distinguished from all congeners by the presence of a distinct medial indent on the edge of the rostral cap.

Description.— Morphometrics and meristics in Table 2. Mouth subterminal, weakly oblique to nearly horizontal. Maxillary barbels usually present, rarely absent. Edge of rostral cap with medial indent; rostral cap occasionally with well-developed tubercles. Pectoral fin with 14–16 branched rays. Lateral-line scales and pored scales on caudal fin 31–35 þ 1–3; predorsal scales 9–11; scale rows above lateral line 5; scale rows below lateral line 5 (rarely 6); scale rows between lateral line and pelvic-fin origin 4 –5. Maximum length ¼ 109.8 mm SL.

Dorsum of head and body brown. Dorsal to of side of head light to dark brown; ventral to ł cream = to yellow; cheeks and opercula occasionally silver. Dorsal 1 3 to of flank light to dark brown, with scattered darker = brown spots on scales in some specimens; ventral to 2 3 cream, yellow, or light brown. Brown to black spot on medial portion of caudal peduncle near caudal fin occasionally present. Venter cream, yellow, or light brown. Dorsal fin with dark brown clusters of melanophores forming blotches in middle portions of interradial membranes, distal edge brown; pectoral, pelvic, and anal fins hyaline; caudal fin mostly clear, with scattered melanophores.

Distribution.— Henicorhynchus entmema is distributed in the Chao Phraya and Mae Klong basins in Thailand and the Mekong basin in Cambodia, Lao PDR, Thailand, and Vietnam ( Fig. 9C ).

Remarks.— Tylognathus entmema was described by Fowler (1934), who noted a ‘‘notch’’ on the rostral cap as well as the presence of maxillary barbels and a faint spot at the base of the caudal peduncle. These characters were confirmed in

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our examination of the holotype (ANSP 59092). This ‘‘notch,’’ herein labeled a medial indent in the rostral cap, is shared by the holotype and paratypes of Henicorhynchus lobtatus Smith, 1945 (except for one specimen that also lacks maxillary barbels and a black spot on the caudal peduncle that is herein identified as H. siamensis [USNM 119492, 1 of 3 specimens, 96.5 mm SL]). In the original description of H. lobatus, Smith (1945) noted that each of the paratypes possesses a black spot at the base of the caudal peduncle. The presence of the black spot on the caudal peduncle, in addition to the distribution of the paratypes solely in the Chao Phraya basin (vs. the occurrence of the holotype from the Mekong), led Roberts (1997) to identify these specimens as Cirrhinus caudimaculatus . We have confirmed the presence of the medial indent and maxillary barbels in all of the paratypes examined, exclusive of the one identified as H. siamensis (see above). This set of oromandibular characters in addition to the black spot on the caudal peduncle is shared by several specimens from the Mekong basin (i.e., CAS 79181, CAS 96200, CAS 96195). We also observed a lot (CAS 96195, n ¼ 3) with specimens possessing these oromandibular characters in which there was variation in the presence of the black spot on the caudal peduncle. We consider these specimens with maxillary barbels, a black spot present or absent on the caudal peduncle, and a distinct medial indent on the rostral cap to be conspecific. The oldest available name for this species is Tylognathus entmema ( Tylognathus is a junior synonym of the labeonin genus Bangana Hamilton, 1822 ; see Zhang and Chen, 2006), and we herein recognize this species as Henicorhynchus entmema .

The presence of the spot on the caudal peduncle is uncommon in specimens examined and not restricted to populations from a particular river basin. Smith (1945) hypothesized that the paratypes, which were smaller than the holotype, were young of the year and the spot was lost at adulthood. This trend was generally observed here as well; however, we note relatively large specimens (. 100 mm SL) also may possess this spot, albeit rarely.

The types of Cirrhina sauvagei Fang, 1942 (MNHN 8598) and Crossocheilus thai Fowler, 1944 (ANSP 71336) each possess a medial indent in the rostral cap, but lack obvious maxillary barbels. Only one other specimen examined in this study that possesses the medial indent in the rostral cap characteristic of H. entmema similarly lacks maxillary barbels (USNM 119491); all others have maxillary barbels that are either barely exposed or hidden in the corner of the mouth. In light of overall morphological similarities with H. entmema and the large number of specimens examined that possess a medial indent on the rostral cap in addition to maxillary barbels (which can be tiny and hidden in the corner of the mouth), we assign Cirrhina sauvagei and Crossocheilus thai as junior synonyms of this species. The absence of maxillary barbels in these few specimens may be the result of their destruction from previous examinations or possible biological factors (i.e., mutation or hybridization).

Material examined.— (Identified, but not measured if no SL given). Cambodia: Mekong basin: CAS 91609 , 9 , Phnom Penh markets, 11.56258N, 104.91608E, 18 January 1994 ; CAS 94278 , 40 , Stung Treng market, 13.51678N, 105.96678E, 2 February 1994 ; CAS 94322 , 21 , rapids in Se San or Tonle San , 7 km upstream from Stung Treng, 13.81328N, 106.258E, 5 February 1994 ; CAS 96185 , 2 , Tonle Sap at km 12 from

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Copeia 108, No. 3, 2020

Phnom Penh?, 11.64488N, 104.88058E; CAS 96200 , 2 (of 6), 81.1–82.3 mm SL, O Champha, 4–8 km upstream from its mouth into Tonle San (near Te Veng, Ratanakiri prov. ), 14.10068N, 107.13528E, 14 April 1994 ; UF 190436 , 1 , 87.4 mm SL, Stung Treng , Tonle Kong approximately 10 km upstream of confluence with Tonle Srepok, 13.60968N, 106.09228E, 22 May 2016 ; UF 190963 , 2 , 96.8–101.4 mm SL, Stung Treng , morning market, 13.53068N, 105.97108E, 22 May 2016 ; UMMZ 232355 , 4 , Stung Treng , Mekong river rapids 7 km downstream from the mouth of the Tonle San, 13.53338N, 105.958E, 29 January 1995 ; UMMZ 232580 , 3 , Stung Treng , Mekong river rapids 7 km downstream from the mouth of the Tonle San, 13.53338N, 105.958E, 16 February 1995 ; UMMZ 232673 , 1 , Kompong Chhnang, Tonle Sap at Kompong Chhnang, fishing lot 9 in second channel east of town, 12.26678N, 107.78338E, 27 February 1995 ; UMMZ 234365 , 4 , Kandal, Prek Phnov at crossing under road #5 along bank of Tonle Sap, 11.88078N, 104.77958E, 22 January 1996 ; UMMZ 234682 , 66 , Stung Treng , Mekong River, shallow channel across the S end of Kaoh Han (Han Island), 14 km NE of Stung Treng, 13.66218N, 106.04368E, 14 February 1996 ; UMMZ 235114 , 5 , Kandal, Tonle Sap River 35 km upstream from Phnom Penh, day row 1, net A, 11.88078N, 104.77958E, 16 January 1995 ; UMMZ 235116 , 1 , Kandal, Tonle Sap at Dai fishery row 9, 25 km upstream from Phnom Penh , 11.88078N, 104.77958E, 22 January 1996 ; UMMZ 235476 , 4 , Kandal, Stung Kandal, 1 km upstream from its junction with Prek Thnot, 11.48478N, 104.94848E, 24 January 1996 ; UMMZ 235503 , 4 , Kandal, Tonle Sap at Dai fishery row 9, 15 km upstream from Phnom Penh , 11.68518N, 104.85288E, 27 January 1996 ; UMMZ 235563 , 164 , Stung Treng , Tonle San rapids at Kaoh Dan Man, 20 km ENE of Stung Treng, 13.56678N, 106.11678E, 10 February 1996 ; UMMZ 235583 , 1 , Stung Treng , Mekong River on W edge of Kaoh Han (Han Island), 16 km NE of Stung Treng, 13.63338N, 106.058E, 12 February 1996 ; UMMZ 235600 , 19 , Tonle San rapids at Kaoh Dam Man, 20 km ENE of Stung Treng , 13.56678N, 106.11678E, 15 February 1996 ; UMMZ 235720 , 2 , Kandal, Tonle Sap, fishing lot 8, 35 km upstream from Phnom Penh , 11.73338N, 104.83338E, 1 March 1996 ; UMMZ 246538 , 1 , Pursat, Pursat River at crocodile pool and in riffles below, 12.358N, 103.16678E, 23 February 2005 ; UMMZ 251890 , 13 , Kandal, Prek Muk Kandal, across Tonle Sap from Phnom Penh , 1 March 1996 . Lao PDR: Mekong basin: CAS 92422 , 1 , Kinnak market, 7 February 1994 ; CAS 92516 , 17 , Sekong watershed , small mountain stream entering right side of Se Kaman just upstream from Se Kaman, 14 April 1995 ; CAS 94931 , 1 , Mekong at Bang Hang Khone, 13.96758N, 105.92988E, March 1995 ; CAS 94936 , 11 , same as CAS 94931 ; CAS 94942 , 9 , Mekong River at Ban Hang Khone, just below Khone Falls, 13.96758N, 105.92988E, June 1993 ; CAS 96194 , 2 , Se Khone, 15.86338N, 106.31318E, August 1993 ; CAS 96195 , 3 , 89.6–109.8 mm SL, Mekong River at Bang Hang Khone, just below Khone Falls, 13.93338N, 105.93338E, June 1993 ; CAS 96199 , 1 (of 2), 79.5 mm SL, Champasak, Sekong watershed , Houay Khaliang near Ban Napakiap, Muang Khong, September 1995 ; CAS 96204 , 1 , 75.5 mm SL, same as CAS 96195 ; UF 185139 , 1 , 70.2 mm SL, Champasak, Pathumporn fish market in Pakse, 15.12028N, 105.79908E, 6 January 2013 ; UMMZ 235346 , 3 , Champasak, Mekong River at Ban Hang Khone, just downstream from Khone Falls, 13.93338N, 105.93338E. Thailand: Chao Phraya basin : ANSP 59092 , 1 , holotype of

Ciccotto and Page—Revision of Henicorhynchus

Tylognathus entmema , 46.4 mm SL, Bangkok, Silom Canal, 13.75408N, 100.50148E, 18 December 1932; ANSP 71336 , 1 , holotype of Crossocheilus thai , 77.4 mm SL, Bangkok, 13.75408N, 100.50148E ; UMMZ 231994 , 5 (of 500), Nakom Sawan, creek under Hwy 1 bridge, 30 km S of Nakom Sawan, 15.40218N, 100.13648E, 23 October 1975 ; UMMZ 233686 , 1 , Pak Hai flood fishery, 14.45748N, 100.36998E ; UMMZ 233688 , 2 , same as UMMZ 233686 ; UMMZ 236743 , 3 , Ping River below Blaumipol Dam at guesthouse, 17.24068N, 98.98158E, 8 May 1965 ; UMMZ 236835 , 5 , Bungboraphet Swamp , Nakhon Sawan, tributary of Nan River, 15.70618N, 100.23218E, 9 February 1965 ; UMMZ 236991 , 15 , same as UMMZ 236835 ; UMMZ 237254 , 1 , Bung Boraphet, trib. to Nan River , Nakhon Sawan, 15.70618N, 100.23218E, 11 November 1964 ; UMMZ 251882 , 1 , same as UMMZ 236743 ; UMMZ 251892 , 2 , Chai Nat, flood plain fishery, 15.18648N, 100.12358E ; USNM 107850 , 4 , Mechem River , tributary of Meping, 11 July 1935 ; USNM 119491 , 1 , paratype of H. lobatus , 66.8 mm SL, Menam Chao Phraya, Pankmanko, 19 November 1923 ; USNM 119492 (in part), 2, paratypes of H. lobatus , 67.4–83.7 mm SL, Bung Borapet, 20 November 1923 ; USNM 119493 , 2 , paratypes of H. lobatus , 58.1–59.2 mm SL, Menam Chao Phraya Bangsai, 27 November 1923 ; USNM 119494 , 1 , paratype of H. lobatus , 72.1 mm SL, Pasak River at Dha Luang, 14.558N, 100.76678E, 20 August 1923 . Mae Klong: UMMZ 195845 , 75 , Mae Nam Mae Klong at Kanchanaburi (confluence of the 2 Mae Nam Khwae rivers), 14.00328N, 99.55018E, 23 March 1965 ; UMMZ 195888 , 4 , Mae Nam Mae Klong at Ban Pong , 2 km downstream, 13.75728N, 99.84748E, 25 March 1965 ; UMMZ 236715 , 8 , Khwae Noi , 4 km from Kanchanaburi, 14 April 1965 ; UMMZ 251885 , 1 , Mae Nam Khwae Noi , ca. 20 km upstream from Kanchanaburi (purchased from fisherman), 14.07948N, 99.42348E, 23 March 1965 ; UMMZ 251897 , 22 , Rajburi, Mae Nam, Mae Klong River , vicinity of Rajburi (purchased in market at Rajburi), 13.53078N, 99.82408E, 14 November 1964 . Mekong basin : CAS 79181 , 13 , mouth of Huay Ngao where it flows into Mekong, 1 km south of Ban Chaem Pong (ca. 30 km southeast of Chiang Khong ), 20.141968N, 100.52698E, 12 May 1990 ; CAS 79182 , 5 , 62.5–94.7 mm SL, Menam Kok at Tha Ton and up to 20 km downstream, 20.0398N, 99.47688E, 15 May 1990 ; CAS 79183 , 3 , Mekong mainstream rapids ca. 4 km downriver from Pak Ing (ca. 25 km downriver from Chaing Kong), 20.18338N, 100.48168E, 10 May 1990 ; CAS 79184 , 2 , Mekong River mainstream near Ban Ha Bia , 30–40 km NE of Chiang Khan on highway 2186, 18.04288N, 101.85628E, 12 March 1990 ; CAS 79186 , 3 , Khong Chiam market, 15.32188N, 105.49428E, 24 December 1988 ; CAS 91768 , 9 , Menam Chi at/near Maha Chana Chai , 15.52488N, 104.24948E, 13 March 1991 ; CAS 91770 , 25 , Yasothon market (¼ Menam Chi ), 15.79718N, 104.13538E, 13 March 1991 ; CAS 91751 , 1 , Pakmenam Mun, May 1991 ; CAS 91771 , 28 , same as CAS 91770 ; CAS 94628 , 1 , mouth of Huay Ngao where it flows into Mekong 1 km south of Ban Chaem Pong (ca. 30 km southeast of Chiang Khong ), 20.1428N, 100.52698E, 12 May 1990 ; CAS 96186 , 3 , Mekong River mainstream rapids ca. 12 km south of That Phenom , 16.84838N, 104.75878E, 6 April 1991 ; CAS 96197 , 1 , 97.9 mm SL, Pak Menam Mun (mouth of Mun R.), 15.31628N, 105.50558E, 26 May 1991 ; CAS 96206 , 1 , Mekong mainstream near Chiang Saen, 20.27548N, 100.08928E, 1 May 1991 ; UF 238787 , 1 , Chiang Rai, Mae Kong , roadside market highway 1129 at km 46-47, 20.23838N, 100.12568E, 15 May

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2010; UMMZ 224348 , 1 , Nakon Phanom, Mekong River, island off Ban Tha Kai , 20 km downstream from Mukdahan, 1 km from Thai , 5 km from Laos side, 16.38458N, 104.87538E, 25 June 1975 ; UMMZ 235124 , 1 , Ubon Ratchathani, Huay Mark Tai, 1 km from Mekong River, Huay Mark Tai flows into Mekong 0.5 km downstream from Mun-Mekong confluence, 15.76678N, 106.18E, 16 October 1975 ; UMMZ 236948 , 3 , Pong Need, trib. of Pong River , 16.758N, 102.58E ; UMMZ 236992 , 5 , Khon-kaen, Pong Neeb, trib. Pong River , 16.758N, 102.58E, 5 October 1964 ; UMMZ 251886 , 5 , Ubon Ratchathani, Huay Thom-loe, at Ban Bung Khee-lek, 7 km E of Khemerat, 2.5 km from Mekong River , 30 September 1975 ; USNM 119490 , 1 , holotype of H. lobatus (photographs), 96.7 mm SL, Mekok River near Chiang Rai, Chiang Rai Prov. , 2 March 1924 ; USNM 271291 , 4 , Ubon Ratchathani, market in fishing village at Ban Dan , 15.328N, 105.58E, 14 March 1972 ; USNM 331910 , 1 , Mun River at Bung Wai about 7 km W of Ubon, Ubon Ratchathani Prov. , 15.20838N, 104.7928E, 14 September 1971 . Vietnam: Mekong basin: UMMZ 217914 , 1 , My Tho Prov, My Tho, Vam Ky Hon , 19 June 1974 ; UMMZ 218653 , 1 , An Giang, Bassac River , 1.3 km S of Long Xuyen, LF-4, 10.3758N, 105.4518E, 28 October 1974 ; UMMZ 227578 , 1 , Phong Dinh Prov , canal in city of Can Tho, 200 m from bridge on main stream ( NR 10 ), 10.08648N, 105.71748E, 15 July 1974 ; UMMZ 235118 , 2 , Phong Dinh, Bassac River at Can Tho, CF-8, 10.03338N, 105.78338E, 3 November 1974 ; UMMZ 235119 , 2 , An Giang, Bassac River , 1 km S of Long Xuyen, LF-3, 10.36498N, 105.45918E, 28 October 1974 ; UMMZ 235120 , 13 , Phong Dinh, Bassac River at city of Can Tho, CF-4, 10.03338N, 105.78338E, 3 November 1974 ; UMMZ 245418 , 1 , An Giang, Bassac River, around Vam Nao town , 10.53338N, 105.33338E, 18 April 1999 ; UMMZ 251891 , 13 , Chau Doc, south end of Vinh Tuong Island, Bassac River , 10.78N, 105.11678E ; UMMZ 251893 , 4 , Phong Dinh, Bassac River at Can Tho, CF-2, 10.03338N, 105.78338E, 3 November 1974 ; UMMZ 251894 , 1 , Chau Doc fish market, 10.78N, 105.11678E, 11 October 1974 . Mainland Southeast Asia: Mekong basin: MHNH 8598 , syntype of Cirrhina sauvagei (photographs), Mekong River , 1874 .

Figures

FIG. 5. Henicorhynchus entmema. (A) ANSP 59092, holotype, 46.4 mm SL, (B) USNM 119490, holotype of H. lobatus, 96.7 mm SL. Images not to scale. Photo A by K. Luckenbill (ANSP); photo B by S. Raredon (USNM).

FIG. 9. Distributions of georeferenced specimens examined of: (A) Henicorhynchus caudiguttatus and H. ornatipinnis, (B) H. caudimaculatus, (C) H. entmema, and (D) H. siamensis.