Balantiocheilos melanopterus

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 : 114-118

A. Balantiocheilos melanopterus

2 mm

·

from the centrum. This character is inapplicable to non-otophysan outgroups that lack a lateral process on the second vertebral centrum.

93. Shape of the tripus ( Sawada, 1982: character 38): (0) triangular; (1) Y-shaped (CI = 1.00; RI = 1.00).

In members of the family Balitoridae and Nemacheilidae the tripus is a Y-shaped element ( Sawada, 1982). In other cypriniform fishes and in other otophysans, the tripus is a roughly triangular element. This character is inapplicable to non-otophysan outgroups.

94. Neural spine of fourth vertebral centrum (Caven- der & Coburn, 1992: character 25): (0) similar in size or smaller than more posterior spines; (1) larger than more posterior spines; (2) absent (CI = 0.67; RI = 0.92).

In certain members of the family Botiidae the neural spine on the fourth vertebral centrum is much larger than the neural spines on more posterior centra. In other cypriniform fishes and in outgroup taxa the neural spine of the fourth vertebral centrum is similar in size or smaller than the neural spine on more posterior centra ( Fig. 36). In members of the genus Psilorhynchus , except for P. robustus , the neural spine of the fourth vertebral centrum is completely absent ( Fig. 14A–C, E, F ), and as such this character is inapplicable. Absence of the fourth neural spine is a highly derived and unusual feature that is rare amongst ostariophysans (Britz & Conway, 2009).

95. Connection between lateral process of the second vertebral centrum and the outer arm of the os suspensorium: (0) no contact between lateral process of the second vertebral centrum and the outer arm of the os suspensorium or contact without fusion of the two structures; (1) ventral arm of the lateral process of the second vertebral centrum fused with the outer arm of the os suspensorium; (2) both dorsal and ventral arms of the lateral process of the second vertebral centrum fused to the outer arm of the os suspensorium (CI = 0.67; RI = 0.95).

In members of the families Catostomidae the ventral arm of the lateral process of the second vertebral centrum is tightly sutured or fused to the outer arm of the os suspensorium ( Bird & Hernandez, 2007; Fig. 36C). In members of the families Balitoridae and Nemacheilidae , and in members of the genus Psilorhynchus , both the dorsal and ventral arms of the lateral process of the second vertebral centrum are fused to the outer arm of the os suspensorium, forming a small lateral opening ( Psilorhynchus ; Fig. 14 ) or pair of lateral openings ( Balitoridae and Nemacheilidae ; Fig. 36H) in the bony capsule surrounding the anterior swim-bladder chamber ( Sawada, 1982). In other cypriniform fishes and in outgroup otophysan taxa the lateral process of the second vertebral centrum does not contact the outer arm of the os suspensorium ( Cyprinidae ; Fig. 36A, B), or the former exhibits simple contact with the latter, without suture or fusion ( Gyrinocheilidae , Botiidae , and Vaillantellidae ; ·

Fig. 36 D-G). This character is inapplicable to nonotophysan outgroup taxa.

96. Supraneural 2: (0) present; (1) absent (CI = 0.33; RI = 0.67).

In members of the families Botiidae and Vaillantellidae , and the nemacheilid Lefua costata , supraneural 2 is absent and the dorsal portion of the neural complex is composed entirely of supraneural 3 ( Fig. 36E, F). In other cypriniform fishes and in nonostariophysan outgroup taxa supraneural 2 is present ( Figs 14 , 36A–D, G, H). Supraneural 2 is also absent in members of the Characiphysi ( Fink & Fink, 1981; Hoffman & Britz, 2006), represented by Distichodus antonii in the present analysis.

97. Supraneural 3 ( Cavender & Coburn, 1992: character 5): (0) with simple median crest, without division; (1) median crest with modified dorsal surface (CI = 0.50; RI = 0.87).

In the leuciscin cyprinids and certain members of the family Balitoridae , the median crest along the dorsal surface of supraneural 3 is bifurcated ( Fig. 36B). In other cypriniform fishes and in otophysan outgroup taxa the median crest along the dorsal surface of supraneural 3 is a simple shaft of membrane bone ( Figs 14 , 36A, D–H). In nonostariophysan outgroups supraneural 3 is a simple strut of bone, similar in shape to more posterior supraneurals. In members of the family Gyrinocheilidae supraneural 3 exhibits additional lateral processes of membrane bone that extend from the surface of the endochondral portion of the bone ventrolateral to the median membrane bone crest along its dorsal surface ( Fig. 36D). As these processes are completely separate from the median crest, the two species of Gyrinocheilus were coded as exhibiting the plesiomorphic condition for this character.

98. Supraneural 3/supraneural 5 contact ( Cavender & Coburn, 1992: character 18): (0) absent; (1) present (CI = 1.00; RI = 1.00).

In the leuciscin cyprinids supraneural 5 is much larger than more posterior supraneural elements, and its anterior edge is closely associated with the bifurcated dorsal surface of supraneural 3 ( Fig. 36B). In other cypriniform fishes and in outgroup taxa supraneural 3 and supraneural 5 (when present) are not closely associated ( Fig. 36A, C–E). This character is inapplicable to taxa that lack supraneural 5.

99. Claustrum: (0) posterodorsal edge not sutured to anterior edge of neural complex; (1) posterodorsal edge sutured to anterior edge of neural complex (CI = 0.50; RI = 0.95).

In members of the Cobitoidea , excluding members of the family Catostomidae , the claustrum is a large element that rims the entire anterior edge of supraneural 2, or supraneural 3 when the former is absent ( Fig. 36E, F, H). In other cypriniform fishes and outgroup otophysan taxa the claustrum is a small vertically oriented bone that makes little contact with the anterior edge of supraneural 2 ( Figs 14 , 36A–C). This character is inapplicable to non-otophysan outgroup taxa.

100. Dorsal prezygapophysis of fifth vertebral centrum (modified from Smith, 1992: character 11): (0) dorsal prezygapophysis of fifth vertebral centrum widely separate from neural arch of fourth vertebral centrum; (1) dorsal prezygapophysis of fifth vertebral centrum abutting neural arch of fourth vertebral centrum (CI = 0.50; RI = 0.87).

In members of the families Catostomidae , Gyrinocheilidae , and certain members of the Botiidae , the dorsal prezygapophysis of the fifth centrum contacts the neural spine of the fourth centrum, contributing to the posterior edge of the neural complex ( Fig. 36C, D). In other cypriniform fishes and in outgroup taxa the dorsal prezygapophysis of the fifth ›

centrum, when present, does not make contact with the neural spine of the fourth centrum, when present ( Fig. 36A, B, E–H).

101. Parapophyses ( Sawada, 1982: character 46): (0) autogenous; (1) fused to centra (CI = 0.25; RI = 0.62).

In members of the family Cobitidae the parapophyses are fused with their associated centra ( Sawada, 1982; Fig. 36G). In P. pseudecheneis the parapophyses associated with centra posterior to the seventh or eighth centrum are similarly fused ( Fig. 15C ). In other cypriniform fishes and in outgroup taxa, excluding Hiodon alosoides and Denticeps clupeoides , the parapophyses are autogenous with their associated centra ( Figs 14 , 15A, B , 36A–F, H). In H. alosoides parapophyses are also fused to their associated centra ( Hilton, 2002).

102. Ventral prezygopophyses: (0) ventral prezygopophyses separate from ventral postzygopophyses on caudal vertebrae; (1) ventral prezygopophyses strongly interdigitating with ventral postzygopophyses on caudal vertebrae (CI = 0.5; RI = 0.83).

In members of the families Botiidae , Vaillantella , and the nemacheilids Acanthocobitis cf. zonalternans (Blyth, 1860) and Mesonoemacheilus triangularis (Day, 1865) , the ventral prezygopophyses on caudal centra are elongate structures that extend anteriorly past their associated centrum, and interdigitate with the postzygopophyses of the next anterior vertebral centrum ( Fig. 37C, D ). In other cypriniform fishes and outgroup taxa the pre- and postzygopophyses are short, and there is no interdigitation of these structures between adjacent vertebrae ( Figs 14 , 37A, B ).

Figures

Figure 14. Weberian apparatus of Psilorhynchus, left side in lateral view, illustrating sexual dimorphism of males (i) and females (ii). Anterior to left. A, Psilorhynchus sucatio: (i) male, UMMZ 205346, 37.8-mm standard length (SL); (ii) female, CAS 50289, 39.6-mm SL. B, Psilorhynchus breviminor: (i) male, ZRC 43452, paratype, 32.0-mm SL; (ii) female, ZRC 43452, paratype, 32.0-mm SL. C, Psilorhynchus gracilis: (i) male, UMMZ 205345, paratype, 39.1-mm SL; (ii) female, UMMZ 205345, paratype, 42.1-mm SL. D, Psilorhynchus robustus: (i) male, CMK 17941, paratype, 58.1-mm SL; (ii) female, CMK 17941, paratype, 58.1-mm SL. E, Psilorhynchus balitora, male, UMMZ 244782, 31.2-mm SL. F, Psilorhynchus pseudecheneis, female, KU 29517, 41.5-mm SL. Cartilage highlighted in grey. Abbreviations: Boc, basioccipital; C, claustrum; Epo, epioccipital; Exoc, exoccipital; Lp2 + Oos, fused lateral process of the second vertebral centrum and outer arm of os suspensorium; NA, neural arch; NS, neural spine; PWP, post-Weberian process; Ri, rib; S, scaphium; Sn, supraneural; Soc, supraoccipital; Tr, tripus; V, vertebral centrum. Numbers after abbreviations refer to the vertebral centrum to which the structure is associated.

Figure 15. Schematic representation of the post-Weberian abdominal (i) and caudal (ii) regions of the vertebral column of Psilorhynchus, left side in lateral view. Anterior to left. A, Psilorhynchus sucatio, CAS50289, 21.2-mm standard length (SL). B, Psilorhynchus balitora, UMMZ 244782, 31.2-mm SL. C, Psilorhynchus pseudecheneis, KU 29517, 41.5-mm SL. Intermuscular bones highlighted in grey. Abbreviations: En, epineural; Ep, epipleural; HS, haemal spine; NA, neural arch; NS, neural spine; Pa, parapophysis; PS, pelvic splint; PU, preural centrum; Ri, rib; V, vertebral centrum. Numbers after abbreviations refer to the vertebral centrum to which the structure is associated.

Figure 37. Caudal vertebrae of selected cypriniform fishes, left side in lateral view. A, Catostomus commersonii, UAIC 14172.01, 62.7-mm standard length (SL), vertebral centra 37–40. B, Cobitis cf. taenia, UAIC 14180.17, 55.4-mm SL, vertebral centra 37–40. C, Yasuhikotakia sidthimunki, UAIC 14166.48, 24.1-mm SL, vertebral centra 23–26. D, Vaillantella euepiptera, BMNH 2000.10.25.1301–1332, 60.8-mm SL, vertebral centra 48–51. Abbreviations: DPZ, dorsal prezygopophysis; HS, haemal spine; NS, neural spine; V, vertebral centrum; VPZ, ventral prezygopophysis. Numbers after abbreviations refer to the vertebral centrum to which the structure is associated.