. Bulletin of the Natural History Museum Zoology. . Fig. 1 Outline drawings of oro-labial structure of: A. 5. keterorhynchos, MZB unregistered, mm SI; B. S. holorhynchos, USNM 325389. mm SI; C. S. endecarhapis, MZB 6092, mm SI: D. Lobocheilos bo, BMNH :1. mm SI; E. Tylognathus diplostomus, BMNH :7, mm SI. ELJ=edge of lower jaw; F=frenulum; LL=Iower lip; M=mouth: MLL=median lobe lower lip; PG=postlabial grove; RC=rostral cap; UL=upper lip. rhynchos develop from structure general for labeonin cyprinids, exemplified by Tylognathus diplostoma (Heckel, 1838)
. Bulletin of the Natural History Museum Zoology. . Fig. 1 Outline drawings of oro-labial structure of: A. 5. keterorhynchos, MZB unregistered, mm SI; B. S. holorhynchos, USNM 325389. mm SI; C. S. endecarhapis, MZB 6092, mm SI: D. Lobocheilos bo, BMNH :1. mm SI; E. Tylognathus diplostomus, BMNH :7, mm SI. ELJ=edge of lower jaw; F=frenulum; LL=Iower lip; M=mouth: MLL=median lobe lower lip; PG=postlabial grove; RC=rostral cap; UL=upper lip. rhynchos develop from structure general for labeonin cyprinids, exemplified by Tylognathus diplostoma (Heckel, 1838)(Fig. IE ) and similar to that of Tylognatus nukta (Hora, 1942: Fig. 9b; see Reid, 1985:p. 287 for the assignment ofLabeo nukta toTylognathus). At < 30 mm SI oro-labial structure of individuals of Schismato- rhynchos is like that of T. diplostoma or T. nukta. At about 30 mm SL the cutting edge of the lower jaw elongates, eventually interrupting the connection between the upper and lower lips around the corner of the mouth. At about the same time the fold in the skin which separates the region of the mandibular laterosensory canal from the rest lower labial tissue deepens, eventually forming the structure Weber & de Beaufort (1916) referred to as the frenulum. Rather than connecting the lower lip to the gular region, this frenulum houses the mandibular laterosensory canal. As the cutting edge of the lower jaw elongates, the portion of the lower lip between the lateral edge of the lower lip and the principle lobe of the lower lip regresses, completely in the two new species, nearly so in S. keterorhynchos. Elongation of the cutting edge of the lower jaw progresses farther in S. holorhynchos and S. heterorhynchos and their mouths are more crescentic than that of S. endecarhapis; they are probably each other's closest relative. Nukta Hora is considered by some recent authors to be a synonym of Schismatorhynchos (Jayaram, 1981; Eschmeyer & Bailey, 1990; Talwar & Jhing
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