Henicorhynchus caudiguttatus ( 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 caudiguttatus ( Fowler, 1934)

Spotted Mud Carp

Figure 3

Crossocheilus caudiguttatus Fowler, 1934:137 , fig. 103. Type locality: Thailand, Chieng Mai. Holotype: ANSP 58452 .

Diagnosis.— A member of Henicorhynchus distinguished from other members of the genus ( Table 1) by the following combination of characters: mouth terminal, strongly oblique (35–458 to midline of body); maxillary barbels present; edge of rostral cap straight, without medial indent; flank immaculate, without longitudinal stripes; caudal peduncle with small brown spot at medial insertion of caudal fin; caudal fin with scattered brown spots in larger specimen (holotype, 59.8 mm SL).

Comparisons.— Henicorhynchus caudiguttatus is distinguished from all other species of Henicorhynchus by the presence of brown spots on the caudal fin in larger specimens. Henicorhynchus caudiguttatus is further differentiated from all other species of Henicorhynchus except for H. siamensis by the presence of a terminal, strongly oblique mouth. Unlike H. siamensis , H. caudiguttatus possesses maxillary barbels.

Description.— Morphometrics and meristics in Table 2. Mouth terminal, strongly oblique. Maxillary barbels present. Edge of rostral cap straight, without medial indent. Pectoral fin with 15 branched rays. Lateral-line scales and pored scales on caudal fin 32 þ 2; predorsal scales 8–10; scale rows above lateral line 5; scale rows below lateral line 4 –5; scale rows between lateral line and pelvic-fin origin 4. Maximum length ¼ 59.8 mm SL.

Dorsum of head and body brown. Dorsal of side of head light brown; ventral = ł cream to yellow; cheeks and opercula silver. Dorsal 1 3 of flank = brown, with scattered darker brown spots on scales; ventral 2 3 silver. Faint brown spot on medial portion of caudal peduncle near caudal-fin insertion in holotype. Venter cream to yellow; breast silver. Dorsal fin with dark brown clusters of melanophores forming blotches

Ciccotto and Page—Revision of Henicorhynchus 489 in middle portions of interradial membranes, distal edge brown; pectoral, pelvic, and anal fins hyaline; caudal fin with scattered brown spots in holotype, hyaline in other specimens.

Remarks.— Roberts (1997) recognized H. caudiguttatus as a junior synonym of H. caudimaculatus ( Fowler, 1934) , noting that only the spotted caudal fin of the holotype of H. caudiguttatus differentiated this specimen from the type of H. caudimaculatus . No other specimen of Henicorhynchus examined here possesses similar spots on the caudal fin. The mouth positions of the type specimens of these two species also vary, with H. caudiguttatus possessing a terminal, strongly oblique mouth vs. a subterminal, weakly oblique (less than 208 to midline of body) to nearly horizontal mouth in H. caudimaculatus . Based on differences in mouth position and caudal-fin coloration, we recognize H. caudiguttatus as a valid species. This species has only been collected once, despite more recent collections throughout Chiang Mai province.

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Distribution.— Henicorhynchus caudiguttatus is known only from the type locality of Chiang Mai in northern Thailand ( Fig. 9A ).

Material examined.— Thailand: Chao Phraya basin: ANSP 58452 , 1 , 59.8 mm SL, Chieng Mai, on Me Nam Ping, North Siam, 5 February 1933 ; ANSP 59089 , 2 (of 3), 30.3–34.0 mm SL, same as ANSP 58452 .

Figures

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

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