Chanodichthys oxycephalus (Bleeker, 1871)

Chen, Xiao, Su, Shiping, Zhang, Xiaohua, Van der Laan, Richard & Zhang, E, 2025, Types matter: taxonomic status of Chanodichthys oxycephalus (Bleeker, 1871) (Cypriniformes, Xenocyprididae) and some relevant species of East Asia, ZooKeys 1257, pp. 285-303 : 285-303

Chanodichthys oxycephalus (Bleeker, 1871)

Culter oxycephalus Bleeker, 1871 a: 74, pl. 5 (Chang-Jiang, China). Appeared first as name only in Bleeker 1870: 252. Also appeared in Bleeker 1871 b: 87 and Bleeker 1873: 10.

Culter oxycephaloides Kreyenberg & Pappenheim, 1908: 104 (Lake Dongting, south central China); Compilation Group XNC 1984: 53 –54 (Xichuan); Yang 1987: 61–62 (Lake Liangzi); Wu 1989: 66–67 (Chishui); Institute SFR and Department of Biology SNU 1992: 44 –45 (Xunyang, Xixiang, Baihe, Ankang); Luo 1994: 47 (Chang-Jiang); Chen et al. 1998 (mid-upper Chang-Jiang basin); Yao 2010: 37 (Anqing, Chaohu, Chang-Jiang); Guo et al. 2021: 164–167 (Guangyuan, Nanchong, Yibin); Wu et al. 2021: 98–99 (Xinhua, Hengyang); Wang 2022: 128 (Nanjing); Chen and Fu 2024: 122–123 (Xinjian, Duchang, Poyang).

Erythroculter oxycephaloides : Nichols 1928: 30 (Lake Dongting); Yih and Chu 1959: 87 (Lake Liangzi); Wu 1964: 103 (Lake Liangzi, Yunxian, Mudong, Hechuan).

Culter ( Erythroculter) oxycephaloides : Kimura 1934: 107 ( Chongqing).

Specimens examined.

• MNHN 0000-5050 , holotype, 290 mm SL: Chang-Jiang ; • ZMB 16686 , 172 mm SL: Lake Dongting (photographic examination) ; • IHB 201807055611–14 , 8 specimens, 65.9–122.4 mm SL: Hunan Province: Xiangyin County, Menggu Village ( 28°48'04.88"N, 112°53'28.42"E), caught by X. Chen, C. An, W. Shao, 5 Jul 2018 ; • IHB 201805055611–14 , 3 specimens, 65.9–122.4 mm SL: Hunan Province: Yueyang City, Chenglingji ( 29°26'09.73"N, 113°08'43.87"E), collected by X. Chen, D. T. Nguyen, L. Zhang, 10 May 2018 . • IHB 201807165611–14 , 4 specimens, 65.9–122.4 mm SL: Hunan Province: Yueyang City, Hongqihu ( 29°13'56.86"N, 112°57'11.99"E), collected by X. Chen, L. Cao, L. Qiu, 16 Jun 2018 .

Diagnosis.

Chanodichthys oxycephalus can be diagnostically separated from all congeneric species by its reduced vertebral count (4 + 37-38), and distinguished from other species, except morphologically similar congeners Ch. dabryi and Ch. abramoides , by having a sub-superior and oblique mouth and 23–29 branched anal-fin rays. It is distinct from the latter two species in having a pointed (vs non-pointed), steeply (vs – gradually) elevated humpback behind to the head and higher lateral-line pored scales 73–75 (vs ≤ 70).

Description.

Morphometric measurements for examined specimens in this study provided in Table 1 . See Fig. 1 for general appearance.

Body strongly compressed and deep; dorsal profile convex with a significant hump posterior to nape and ventral profile somewhat straight. Abdominal keel developed from the pelvic-fin insertion to the anus. Head small, pointed, laterally compressed, length less than body height. Snout protruded, longer than eye diameter. Mouth sub-superior, slit; maxilla slightly shorter than mandible, with its posterior end extending backwards below nostril but not to anterior margin of orbital. No barbels. Eye large, laterally positioned in anterior half of head. Interorbital space wide and slightly convex, distance larger than eye diameter. Nostril near anterior margin of eye, with lower margin above a line aligning upper margin of eye. Gill aperture broad, extending forward approximately below posterior margin of eye. Gill membranes united to narrow isthmus.

Dorsal fin with 3 simple and 7–8 branched rays; last simple ray stiff with a smooth posterior margin, and shorter than HL; origin posterior to vertical through pelvic-fin base; distal margin slightly concave. Pectoral fins short and pointed, with 1 simple and 15–16 branched rays; tip of adpressed fin rays not reaching pelvic-fin insertion. Pelvic fin with 2 simple and 8 branched rays, inserted anterior to dorsal-fin origin, or midway between pectoral-fin insertion and anal-fin origin; tip of adpressed fin rays not reaching anal-fin origin. Pelvic axillary scale present, short, not reaching beyond base of last ray. Anal fin with 3 simple and 23–26 branched rays; origin posterior to vertical through posterior end of dorsal-fin base, or much closer to pelvic-fin base than to caudal-fin base, distal margin slightly concave. Caudal fin deeply forked, longest rays more than twice as long as shortest rays, and upper and lower lobes pointed.

Lateral line complete, originating from upper extremity of gill opening, descending downwards above pectoral-fin base, and extending almost straightly along the mid-lateral of body, running parallel to the ventral margin onto caudal peduncle. Perforated scales 73 (14) or 75 (16); scale rows above lateral line 13 (30) and below 7 (30); circum-peduncular scales 21 (16) or 22 (14) and pre-dorsal scales 13 (30).

Coloration.

In freshly collected specimens, head and dorsum of body grey-black, underside and abdomen silver; back and lateral head peppered with small dark spots. Back darker and belly lighter. Fins reddish, caudal fin orange-red.

In formalin-stored specimens, ground color slightly faded; body dorsally greyish and ventrally greyish-white and back of head becoming yellowish-brown. Fins grey to creamy yellow.

Sexual dimorphism.

No sexual dimorphism was observed in the specimens checked.

Geographical distribution and habitat.

Chanodichthys oxycephalus is restricted to the Chang-Jiang basin (Fig. 2 ), based on the data obtained during the field survey and historical records from the literature ( Compilation Group XNC 1984 ; Yang 1987; Wu 1989; Institute SFR and Department of Biology SNU 1992 ; Yao 2010; Duan et al. 2015; Guo et al. 2021; Wu et al. 2021; Wang 2022; Chen and Fu 2024). Specimens, previously identified by Luo and Chen (1998) as Culter oxycephaloides from the mid-upper Chang-Jiang basin, belong to this species; meanwhile, the voucher specimens, recognized by them as Ch. oxycephalus from Lake Liangzi of Hubei Province and Lake Shinkai of Heilongjiang Province, are in fact a misidentification of Ch. dabryi .

Figures

Figure 1. Lateral view of Chanodichthys oxycephalus, ca 250 mm TL; China: Jiangsu: Nanjing, Jul 2021, collected by Tao Ju and Zhaochen Ding. Illustrated by Zhixian Sun.

Figure 2. Distribution map of Chanodichthys oxycephalus (green area) and related records compiled from historical literature and field surveys. Note: red solid circles = valid records; crossed circles = literature-derived invalid historical records. The grey region delineates the sympatric distribution of cultrin fishes, viz., the studied area.