Paralaubuca Bleeker, 1864

Tangjitjaroen, Weerapongse, Randall, Zachary S., Yang, Lei, Grudpan, Chaiwut & Page, Lawrence M., 2025, Taxonomic revision of Paralaubuca (Cypriniformes, Xenocyprididae), a taxon seemingly in decline, Zootaxa 5647 (4), pp. 301-330 : 316

Paralaubuca Bleeker, 1864

Paralaubuca Bleeker, 1864:15 . Type species: Paralaubuca typus Bleeker, 1864 by monotypy.

Cultrops Smith, 1938:410 . Type species: Culter siamensis Hora, 1923 by original designation.

Elongate, strongly compressed body (mean width/SL=8.4–8.6%) with ventral keel from head to anus, fleshy flap at base of pectoral fin, and large, modified scale at base of pelvic fin. Last simple ray of dorsal fin thin and flexible. Body moderately deep at dorsal-fin origin (mean depth/SL=25.0–28.5%) and slender posteriorly (mean caudalpeduncle depth/SL=10.5–12.5%). Predorsal profile arching anteriorly, then straight to dorsal fin. Ventral profile curving downward from tip of lower jaw and along ventral keel, then rising posteriorly to caudal peduncle. Mouth strongly oblique, ~70–80 degrees to longitudinal axis of body.

Lateral line, when continuous, extends downward from head to fourth scale row above pelvic-fin origin, then turning upward and continuing above anal fin to middle of caudal peduncle. Lateral line often discontinuous, in two segments, with anterior segment typically extending several scales past posterior segment. Anal fin extending from anus to caudal peduncle, with second unbranched and first one or two branched rays longest, branched rays gradually decreasing in length posteriorly. Pectoral fin long (mean length/SL=24.3–25.1%), and pelvic fin short (mean length/SL=13.4–14.5%). Caudal fin forked, with 0–4 pored scales following lateral line. Colors of recently collected and preserved specimens are shown in Figure 1 .

Species of Paralaubuca resemble species of Parachela and Oxygaster , with which they are sometimes collected, but are easily distinguished by the presence (vs. absence) of a flap at the base of pectoral fin ( Figure 2 ). Also, in Parachela the epaxial musculature extends anteriorly at least to the middle, and usually past the anterior margin of eye, and in Oxygaster it extends anteriorly to the posterior margin of eye; in Paralaubuca the epaxial musculature extends only to the back of head, not reaching posterior margin of eye. Oxygaster typically has longitudinal black bands on caudal fin which are absent in Paralaubuca .

Figures

FIGURE 1. Paralaubuca typus, (A) live, UF 248615, 95.6 mm SL, Ping River, Kamphaeng Phet Province, Thailand, 8 Feb 2022. (B) preserved, UF 193797, female, 123.6 mm SL, and (C) preserved male, 116.1 mm SL, Ping River, Kamphaeng Phet Province, Thailand, 10 Feb 2024. Paralaubuca barroni, (D) preserved, UF 249886, 72.9 mm SL, Mekong River, Ubon Ratchathani Province, Thailand, 16 Jul 2005. Paralaubuca harmandi, (E) live, UF 248526, 126.1 mm SL, Chao Phraya River, Ayutthaya Province, Thailand, 21 Jun 2022.

FIGURE 2. Paralaubuca typus, UF 249413, 54.4 mm SL. (A) pectoral-fin flap, (B) black dots on pores on lateral-line scales illustrating overlap in a discontinuous lateral line.