Psilorhynchus kuwana

Conway, Kevin W., 2018, ‘ On Psilorhynchus sucatio and P. nudithoracicus’, the sequel: Unnecessary and unscientific names lead to rapid synonymization and taxonomic time wasting-A response to Arunachalam et al. (2018), Zootaxa 4418 (6), pp. 594-600 : 595

Problems with the diagnosis of Psilorhynchus kuwana

Arunachalam et al. (2018) described P. kunawa based on 16 specimens collected from a single location (Kuwana River, Pathar Village, Devario District, Uttar Pradesh, India). Based on the characters listed in the description of P. kuwana (Arunachalam et al., 2018: 218–222) and based on the gestalt of the holotype (Arunachalam et al., 2018; Fig. 5) it is apparent that this species is very similar in external appearance to P. sucatio (compare the holotype specimen of P. kuwana shown in figure 5 of Arunachalam et al., 2018 with any specimen of P. sucatio illustrated in Conway et al., 2013 [figures 3–7]). In the diagnosis of P. kuwana, Arunachalam et al. (2018: 219) list eight characters ( Table 2) that serve to differentiate the allegedly new species from P. sucatio . Again, critical reappraisal of these characters ( Table 2) reveals the same issues as raised above for P. platydorsalis . The diagnosis of P. kuwana , however, is especially plagued by “ephemeral” characters, which are no longer valid when the actual variation present within P. sucatio is considered. Worryingly, Arunachalam et al. (2018) report the upper jaw to be of widely different lengths in P. kuwana (“11.3–16.5”) and P. sucatio (“26.3–30.1%HL”) and thus of some use in distinguishing between the two species. Given that (1) the length of the upper jaw is relatively uniform across Psilorhynchus (e.g., see Figure 7 in Conway, 2011) and (2) that the upper jaw is not visible externally and cannot be measured accurately using point to point calipers (the method reported by Arunachalam et al., 2018) the differences reported in this character between P. kuwana and P. sucatio by Arunachalam et al. (2018) cannot be explained or credited.

Arunachalam et al. (2018) have failed to provide convincing character evidence that P. kuwana is distinguishable from P. sucatio and therefore P. kuwana is a junior synonym of P. sucatio .