Henicorhynchus Smith, 1945

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 Smith, 1945

Figures 1–8

Henicorhynchus Smith, 1945:256 . Type species: Henicorhynchus lobatus Smith, 1945 , by original designation (also monotypic).

Synonym of Cirrhinus Oken, 1817 — Roberts, 1997.

Synonym of Gymnostomus Heckel, 1843 — Kottelat, 2003.

Diagnosis.— Henicorhynchus is distinguished from other labeonin genera by the following combination of characters: 1) mouth transverse, either terminal or subterminal; 2) rostral cap covering most of upper lip, in some individuals strongly overhanging medial portion; 3) edge of rostral cap smooth or with single medial indent; 4) shallow lateral groove extending obliquely anteriorly from corner of mouth to snout; 5) upper lip adnate to exposed surface of upper jaw and continuous with lower lip around corner of mouth, not covering entire upper jaw; 6) edge of upper lip smooth, without papillae; 7) maxillary barbels present or absent, but rostral barbels always absent; 8) lower lip firmly attached to lower jaw and without fleshy medial cushion or lobe; 9) 8 branched dorsal-fin rays; 10) humeral region immaculate, without distinct blotch.

Description.— Mouth terminal, strongly oblique (35–458 to midline of body), or subterminal, weakly oblique to nearly horizontal (less than or equal to 208 to midline of body). Rostral cap covering most of upper lip; edge with papillae, either straight or with distinct medial notch; tubercles infrequently present on tip of snout. Upper lip thin, fused with upper jaw; continuous with lower lip around corner of mouth; edge with papillae. Lower jaw slightly arched, cornified at edge. Lower lip thin, adnate to jaw; postlabial grooves separating lateral aspects from center. Maxillary barbels present or absent; if present, small and barely exposed at corner of mouth.

Dorsal profile slightly arched; deepest at dorsal-fin origin; ventral profile slightly convex. Head short, longer than wide; snout conical, rounded anteriorly; eyes lateral. Dorsal-fin origin anterior of pelvic-fin origin. Pectoral fins positioned ventrally, reaching approximately to ł distance from origin to = pelvic-fin origin when adpressed. Pelvic fins reaching 2 3 distance = to just anterior to anus when adpressed. Anal fin reaching 2 3 distance or to base of caudal fin when adpressed. Axillary pelvic lobes well developed. Dorsal and anal fins slightly concave to falcate; pectoral and pelvic fins triangular. Caudal fin deeply forked with pointed lobes approximately equal in length.

Dorsal fin with 3 simple and 8 branched rays; anal fin with 3 simple and 5 branched rays; pelvic fin with 1 simple and 8 branched rays; pectoral fin with 1 simple and 13–16 branched rays; caudal fin with 10 þ 9 principal rays, 9 þ 8 branched. Body entirely scaled; scales well developed. Lateral-line scales and pored scales on caudal fin 31–35 þ 1– 4; predorsal scales 8–12; scale rows above lateral line 5 (rarely 6); scale rows below lateral line 4 –5 (rarely 6); scale rows between lateral line and pelvic-fin origin 4 (rarely 5); circumpeduncular scales 20.

Comparisons.— Henicorhynchus is most similar to Gymnostomus (see generic account below), several species currently placed in Cirrhinus , and Lobocheilos . Henicorhynchus is distinguished from Gymnostomus by a rostral cap with a straight edge or single medial indent (vs. rostral cap with fimbriae in Gymnostomus ) and the absence (vs. presence) of rostral barbels. Henicorhynchus is distinguished from species of Cirrhinus sensu Kottelat (2013) , including C. cirrhosus ; C. jullinei Sauvage, 1878 ; C. microlepis Sauvage, 1878 ; C. molitorella ; and C. prosemion ( Fowler, 1934) , by having 8 branched dorsal-fin rays (vs. 9 or more in the aforementioned species of Cirrhinus ). Cirrhinus cirrhosus , C. jullieni , C. molitorella , and C. prosemion all have rostral barbels (vs. rostral barbels absent in Henicorhynchus ). In both C. cirrhosus and C. microlepis , the upper lip covers the entirety of the upper jaw (vs. upper lip adnate to upper jaw). In C. molitorella and C. prosemion , the upper lip possesses distinct papillae along the edge (vs. smooth edge to upper lip in Henicorhynchus ). Henicorhynchus is distinguished from ‘ Cirrhinus ’ inornatus and ‘ C.’ rubirostris (originally described in Cirrhinus by

Roberts [1997] and later placed in Gymnostomus by Kottelat [2013]; see discussion below about generic classification for these two species) by an upper lip adnate to the upper jaw and a cornified sheath on the upper jaw (vs. an upper lip that covers the entire upper jaw), the absence (vs. presence) of a post-oral groove, 8 (vs. 9) branched dorsal-fin rays, and an immaculate humeral region (vs. supracleithral blotch present). Henicorhynchus is distinguished from Lobocheilos by having the lower lip firmly attached to the lower jaw (vs. lower lip with a fleshy medial lobe that is free anteriorly and laterally).

Remarks.— Henicorhynchus is a member of the cyprinid subfamily Labeoninae based on the ventrally expanded rostral fold, the presence of a superficial posterior labial fold, and the presence of a vomero-palatine organ ( Stiassny and Getahun, 2007). The diagnostic characters of Labeoninae reported by Reid (1982), including a terete process on the basioccipital and the direct contact between the neural complex of the Weberian apparatus and the supraoccipital region, could not be examined in specimens on loan to us, but were reported present in H. siamensis by Stiassny and Getahun (2007). Additionally, an incised border on the first anal-fin pterygiophore was observed in radiographs of the holotypes of H. entmema ( Fowler, 1934; ANSP 59092) and H. ornatipinnis ( Roberts, 1997; CAS 91756), and was observed in H. siamensis (Sauvage, 1881) by Stiassny and Getahun (2007), who reported this character as an additional diagnostic character of Labeoninae . Several molecular phylogenies place Henicorhynchus within Labeoninae ( Wang et al., 2007; Yang et al., 2012; Zheng et al., 2012).

The common name ‘‘mud carp’’ is used for several species of Henicorhynchus and C. molitorella , which is often more specifically referred to as the Chinese Mud Carp. We retain the use of mud carp in the common names of species of Henicorhynchus .

Figures

FIG. 1. Lateral views of (A) Henicorhynchus siamensis, CAS 93270, 81.5 mm SL, and (B) H. entmema, CAS 96199, 79.5 mm SL. Dashed lines indicate angle of mouth. Scale bars ¼ 5 mm. Photos by Z. Randall (FLMNH).

FIG. 2. Ventral views of (A) Henicorhynchus siamensis, CAS 93270, 81.5 mm SL, and (B) H. entmema, CAS 96199, 79.5 mm SL. Abbreviations: LL, lower lip; MB, maxillary barbel; RC, rostral cap; UL, upper lip. Scale bars ¼ 1 mm. Photos by Z. Randall (FLMNH).

FIG. 3. Henicorhynchus caudiguttatus, ANSP 58452, holotype, 59.8 mm SL. Photo by K. Luckenbill (ANSP).

FIG. 4. Henicorhynchus caudimaculatus. (A) ANSP 58332, holotype, 41.4 mm SL, (B) USNM 107960, holotype of Cirrhinus lineatus, 108.8 mm SL. Images not to scale. Photo A by K. Luckenbill (ANSP); photo B by S. Raredon (USNM).

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. 7. Henicorhynchus siamensis, ANSP 68069, holotype of Cirrhinus marginipinnis, 113.7 mm SL. Photo by K. Luckenbill (ANSP). = caudal peduncle with small brown spot at medial insertion of opercula occasionally silver. Dorsal 1 to of flank light to 3 caudal fin in smaller specimens; caudal fin mostly clear, with dark brown, with scattered darker = brown spots on scales in scattered melanophores; pectoral, pelvic, and anal fins some specimens; ventral to 2 cream, yellow, or light 3 hyaline in life. brown. Brown to black spot on medial portion of caudal peduncle near caudal-fin insertion in smaller specimens Comparisons.—Henicorhynchus caudimaculatus is most similar (,100 mm SL). Up to seven brown longitudinal stripes on to H. entmema in having a subterminal mouth and maxillary flanks in most specimens; usually distinct in specimens barbels, but differs in having a straight edge on the rostral cap greater than approximately 40 mm SL. Venter cream, yellow, (vs. a medial indent on the rostral cap of H. entmema) and in or light brown. Dorsal fin with dark brown clusters of usually having a series of longitudinal stripes along the flank melanophores forming blotches in middle portions of (vs. flank always immaculate in H. entmema). interradial membranes, distal edge brown; pectoral, pelvic, and anal fins hyaline; caudal fin generally clear, with Description.—Morphometrics and meristics in Table 2. Mouth scattered melanophores. subterminal, weakly oblique to nearly horizontal. Maxillary barbels present. Edge of rostral cap straight, without medial Remarks.—In the original description of H. caudimaculatus, indent; rostral cap occasionally with well-developed tuber- Fowler (1934) noted a ‘‘grayish axial streak’’ along the flank of cles. Pectoral fin with 14–16 branched rays. Lateral-line scales the holotype (p. 126, fig. 90) in addition to a brown spot on and pored scales on caudal fin 31–34þ2–3; predorsal scales 9– the caudal peduncle near the insertion of the caudal-fin rays. 11; scale rows above lateral line 5; scale rows below lateral In similarly sized specimens previously identified as H. lineatus, line 4 –5; scale rows between lateral line and pelvic-fin a similar spot on the caudal peduncle is present and the lateral origin 4. Maximum length ¼ 150 mm SL (Kottelat, 2001). stripes vary from very faint to bold (also noted by Roberts Dorsum of head and body brown. Dorsal of side of head [1997]), with some small specimens also possessing one light to dark brown; ventral ł cream to yellow; cheeks and distinct stripe. The types of Tylognathus caudimaculatus and

FIG. 8. Henicorhynchus siamensis, UF 191421, live, 51.5 mm SL. Photo by Z. Randall (FLMNH).