Psilorhynchus balitora

Conway, Kevin W., Dittmer, Drew E., Jezisek, Laci E. & Ng, Heok Hee, 2013, On Psilorhynchus sucatio and P. nudithoracicus, with the description of a new species of Psilorhynchus from northeastern India (Ostariophysi: Psilorhynchidae), Zootaxa 3686 (2), pp. 201-243 : 231

Psilorhynchus balitora species group

Diagnosis. Members of this species group are distinguished from congeners by the following combination of characters: anteriormost branchiostegal ray greatly reduced, composed of articular head only, or absent; parietal portion of temporal sensory canal with three openings (only two openings present in available material of P. hamiltoni and P. pavimentatus ); articular portion of preopercular-mandibular sensory canal absent; caudal fin weakly forked, with tips of upper and lower lobes rounded.

Included species. P. balitora , P. brachyrhynchus , P. breviminor , P. hamiltoni , P. nepalensis , P. pavimentatus , and P. rahmani .

Remarks. Conway (2011) originally diagnosed the P. balitora group based solely on two osteological characters (anteriormost branchiostegal ray greatly reduced, composed of articular head only, or absent, and postepiphysial fontanelle smaller than preepiphysial fontanelle). We continue to utilize the first of these characters here but no longer consider the second (size of the postepiphysial fontanelle in relation to the preepiphysial fontanelle) to be particularly useful given the size variation that exists in both of these structures across the members of this group ( Fig. 13 F–L). Two additional osteological characters, both from the cephalic sensory canal system, appear also to be useful for recognizing members of this group, when utilized in combination with other characters, including: the absence of the anguloarticular portion of the preopercular-mandibular sensory canal and the presence of three openings in the parietal portion ( Fig. 2 , 13 F–I, K) of the temporal sensory canal (present in all members except for P. pavimentatus and P. hamiltoni ; Fig. 13 J, L). The anguloarticular portion of the preopercularmandibular canal is also absent in P. sucatio , P. pseudecheneis and P. tenura but is invariably present in all remaining members of the P. nudithoracicus group. The third opening in the parietal portion of the temporal sensory canal in not found outside of the P. balitora species group. This opening is located close to the lateral edge of the parietal, on a small branch of the main channel. The surface pore associated with this opening could not be located in any alcohol specimens, suggesting that it may be relatively small.

We follow Conway (2011) and tentatively consider P. amplicephalus , P. gokkyi and P. piperatus to belong to this group, pending further investigation.

Figures

FIGURE 2. Schematic representation of the cephalic sensory system of Psilorhynchus. Only canal bearing bones are illustrated (with exception of supraorbital). See text for explanation. Abbreviations: Ang, anguloarticular; Fr, frontal; IO 1 - 5, infraorbital 1 - 5; Na, nasal; Pa, parietal; Pop, preopercle; Pter, pterotic; So, supraorbital; Soc, supraoccipital.

FIGURE 13. Dorsal surface of the neurocranium of Psilorhynchus sucatio and members of the P. balitora and P. nudithoracicus species groups, showing cranial fontanelle and surrounding bones, anterior to top. A. Psilorhynchus sucatio, CAS 50289, 39.6 mm SL. B. Psilorhynchus melissa, UMMZ 248830, paratype, 49.8 mm SL. C. Psilorhynchus nudithoracicus, UMMZ 205345, 39.1 mm SL. D. Psilorhynchus robustus, CMK 17941, Paratype, 58.1 mm SL. E. Psilorhynchus tenura, uncat., 38.0 mm SL. F. Psilorhynchus balitora, UMMZ 244782, 31.2 mm SL. G. Psilorhynchus breviminor, ZRC 43452, paratype, 32.0 mm SL. H. Psilorhynchus brachyrhynchus, NRM 40922, 38.0 mm SL. I. Psilorhynchus nepalensis, KU 40663, 42.0 mm SL. J. Psilorhynchus pavimentatus, UMMZ 248832, paratype, 48.7 mm SL. K. Psilorhynchus rahmani, ZRC 51437, paratype, 28.9 mm SL. L. Psilorhynchus hamiltoni, UMMZ 249904, paratype, 26.3 mm SL. Cephalic sensory canals illustrated on left side only. Abbreviations: E, ethmoid complex; Fr, frontal; Pa, parietal; Soc, supraoccipital.