Psilorhynchus gracilis

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 : 139-140

PSILORHYNCHUS GRACILIS GROUP

Included species: Psilorhynchus gracilis , P. melissa , and P. robustus .

Diagnosis: Members of this group are characterized by the following osteological characters: pre- and postepiphysial fontanelle long rectangular openings, similar in size and separated only by a narrow strut of frontal dorsal to the epiphysial bar ( Fig. 3D, E ); presence of a short mandibular sensory canal along the ventrolateral face of the anguloarticular ( Figs 7D, E, 8D, E ); a prominent dorsal projection on the third pectoral radial ( Fig. 18D, E); and a hiatus between the proximal tip of hypural 1 and the compound centrum ( Fig. 16D, E ).

Remarks: In addition to the osteological characters listed above, members of this group share the presence of a weakly reticulate colour pattern over the dorsal and lateral body surface. Psilorhynchus tenura , a species recovered in radically different positions in the results of the parsimony and Bayesian analyses ( Fig. 44A, C ), exhibits a similar colour pattern. Although it lacks the mandibular sensory canal, the dorsal projection on the third pectoral radial, and the hiatus between the proximal tip of hypural 1 and the compound centrum, it is tentatively considered a close relative of members of this group based on the shape of its cranial fontanelle, which are strikingly similar in size, shape, and configuration to those of P. gracilis , P. melissa , and P. robustus . Molecular characters may provide further insight on the phylogenetic placement of this biogeographically interesting species of Psilorhynchus .

Figures

Figure 3. Neurocranium of Psilorhynchus in dorsal (i), lateral (left side) (ii), and ventral (iii) view. Anterior to left. A, Psilorhynchus sucatio, CAS 50289, 39.6-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: AV–VII, anterior opening of trigeminal–facial chamber; Apto, autopterotic; Asph, autosphenotic; Boc, basioccipital; BocPr, basioccipital process; E, ethmoid complex; Exoc, exoccipital; Epo, epioccipital; FIX, foramen for glossopharyngeal nerve; Fr, frontal; FX, foramen for vagus nerve; LE, lateral ethmoid; MaPl, masticatory plate of the basioccipital; N, nasal; Orsph, orbitosphenoid; Pa, parietal; PE, prethmoid; Pro, prootic; Psph, parasphenoid; Ptsph, pterosphenoid; PV–VII, posterior opening of trigeminal–facial chamber; Soc, supraoccipital; Sor, supraorbital; STF, subtemporal fossa; Vo, vomer.

Figure 8. Hyopalatine arch and opercular series of Psilorhynchus, right side in lateral (i) and medial (ii) view. Anterior to left (images reversed). A, Psilorhynchus sucatio, CAS 50289, 39.6-mm 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: Ana, anguloarticular; Apa, autopalatine; Cm, coronomeckelian; De, dentary; Ecpt, ectopterygoid; Enpt, endopterygoid; Hy, hyomandibular; Iop, interopercle; MC, Meckel’s cartilage; Mpt, metapterygoid; Mx, maxilla; Op, opercle; Pmx, premaxilla; Pop, preopercle; Q, quadrate; Ra, retroarticular; Sop, subopercle; Sy, symplectic.

Figure 16. Caudal fin skeleton of Psilorhynchus, left side in lateral view. Anterior to left. A, Psilorhynchus sucatio, CAS 50289, 39.9-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, KU 29143, 33.5-mm SL. D, Psilorhynchus robustus, CMK 17941, paratype, 58.1-mm SL. D, P. pseudecheneis, KU 29519, 40.3-mm SL. Cartilage highlighted in grey. Abbreviations: CC, compound centrum; DCRC, distal caudal radial cartilage; *, hypural 5; Ep, eplural; HA, haemal arch; H1–4, hypurals 1–4; HS, haemal spine; NA, neural arch; NS, neural spine; Ph, parhypural; Pls, pleurostyle; PU2–3, preural centra 2–3. Upper- and lowermost principal caudal fin rays are indicated with a black dot.

Figure 44. Intrarelationships of Psilorhynchus. A, Psilorhynchus clade from the strict consensus of the 14 equally parsimonious cladograms obtained from the first parsimony analysis (analysis 1; clade highlighted in grey in Fig. 43). Numbers above branches indicate clades discussed in text. B, the Psilorhynchus clade obtained in the strict consensus of 98 equally parsimonious cladograms obtained from the second parsimony analysis (analysis 2) with the inclusion of Psilorhynchus homaloptera. C, the Psilorhynchus grouping obtained in the Bayesian analysis. Numbers below branches indicate Bremer/bootstrap support for particular clades in A and B, and Bayesian posterior probabilities for nodes (derived from 9500 Markov chain Monte Carlo sampled trees) in C.