Psilorhynchus sucatio

Conway, Kevin W., 2011, Osteology of the South Asian Genus Psilorhynchus McClelland, 1839 (Teleostei: Ostariophysi: Psilorhynchidae), with investigation of its phylogenetic relationships within the order Cypriniformes, Zoological Journal of the Linnean Society 163 (5), pp. 50-154 : 69

A. Psilorhynchus sucatio B. Psilorhynchus balitora the latter bearing a short posterodorsally directed process on its dorsal surface, closer to its medial face than to its lateral face. The posteroventral face of the ventral hypohyal serves as a point of attachment for the ligament attached to the anterior process of the urohyal. There are three branchiostegal rays ( Figs 7A, 12A ). The anteriormost branchiostegal is ·

greatly reduced in length, reaching no further than the posteriormost point of the posterior ceratohyal. It articulates with the medial face of the anterior ceratohyal close to its posteriormost tip. The remaining brachiostegals are long and well developed: both articulate with the lateral face of the posterior ceratohyal. The urohyal is ventrally flattened with a dorsally directed blade-like process extending along the midline, giving the bone an inverted T-shaped appearance in cross section. Two long processes extend from its anterior edge, which attach to the ventral hypohyals by short ligaments.

Comparisons

There are few differences between the hyoid arch of P. sucatio and that of the other species of Psilorhynchus examined, other than in the appearance of individual bones ( Fig. 12 ). The most obvious differences concern the point of articulation between the interhyal and posterior ceratohyal, and the shape of the dorsal hypohyal, anteriormost branchiostegal ray, and urohyal. In all other species examined the posteriormost tip of the posterior ceratohyal is dorsally directed, and exhibits a shallow groove on its medial face for the reception of the interhyal. The process on the dorsal surface of the dorsal hypohyal is also much more developed in other species of Psilorhynchus , and extends towards the antimere, occluding the posteriormost tip of the basihyal in dorsal view. In P. gracilis , P. pseudecheneis , P. robustus , and P. melissa , all three branchiostegal rays are elongate and similar in shape ( Figs 7D–F, 12D–F ). In P. balitora ( Figs 7B, 12B ), P. rahmani , and P. pavimentatus , the anteriormost branchiostegal ray is greatly reduced in length, compared with the remaining rays, and is similar in that respect to the anteriormost branchiostegal ray of P. sucatio . The single cleared and stained specimen of P. nepalensis and two of the three cleared and stained specimens of P. breviminor examined exhibit a reduced anteriormost branchiostegal ray on the left side only ( Fig. 7C), possessing only two elongate branchiostegal rays on the right side. The remaining cleared and stained specimens of P. breviminor and both specimens of P.

Figures

Figure 12. Hyoid bar and branchiostegal rays of Psilorhynchus, right side in lateral view. Anterior to left (images reversed). A, Psilorhynchus sucatio, CAS 50289, 27.4-mm standard length (SL). B, Psilorhynchus balitora, UMMZ 244782, 31.2-mm SL. C, Psilorhynchus breviminor, ZRC 43452, paratype, 32.0-mm SL. D, Psilorhynchus gracilis, UMMZ 205345, paratype, 39.1-mm SL. E, Psilorhynchus robustus, CMK 17941, paratype, 58.1-mm SL. F, Psilorhynchus pseudecheneis, KU 29517, 41.5-mm SL. Cartilage highlighted in grey. Abbreviations: Ach, anterior ceratohyal; BR, branchiostegal rays; DHh, dorsal hypohyal; Ih, interhyal; PCh, posterior ceratohyal; VHh, ventral hypohyal.