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Pseudomystus carnosus ZBK , P. fumosus ZBK and P. moeschii are hypothesized to form a monophyletic group based on their possession of an enlarged and prominent process of the post-temporal that is almost as long as the postcleithral process, which is considered a synapomorphy. The three species also possess long hair-like epithelial projections on the skin and long tubular extensions of the sensory pores. These two characters are shared with a clade comprising Bagrichthys ZBK , Bagroides ZBK and Leiocassis ZBK , and have previously been considered synapomorphies for that clade (Mo, 1991). This raises the possibility that Pseudomystus ZBK as currently understood may not be monophyletic. However, in the light of limited material and evidence available to us, we are unable to investigate this problem in greater depth for now.
Pseudomystus moeschii was originally described from three syntypes (BMNH 1818.104.22.168-66; Boulenger, 1890: 39). Two of the syntypes (BMNH 1889.11.64-65) were found to belong to a different species, which was subsequently described as Pseudomystus breviceps by Regan (1913). Our examination of all three syntypes of P. moeschii indicate that P. breviceps is a distinct species. Given that the type series of P. moeschii consists of more than one species, it is necessary to designate a lectotype for Pseudomystus moeschii in order to stabilize the taxonomy of this species. Therefore, we hereby designate BMNH 1822.214.171.124 as the lectotype of Liocassis moeschii Boulenger, 1890 ZBK .
The difference in the body depth between P. carnosus ZBK and P. fumosus ZBK combined and P. moeschii are not likely to be related to ontogeny, as a biplot of the body depth at anus against SL (Fig. 7) indicates. It can be argued that the state of the preservation and age of the specimens of P. carnosus ZBK available for study preclude any meaningful use of this biometric character as a diagnostic one. However, we note that P. carnosus ZBK actually has a deeper body than either P. fumosus ZBK or P. moeschii , while the shrinkage typically associated with specimens that have been preserved for a long time would dictate that the older specimens(here P. carnosus ZBK ) have a measurably slenderer body. Therefore, although the numbers of specimens examined are too small for any meaningful statistical analysis, we believe that these differences will hold up once more material is made available and studied. The three species can also be clearly distinguished by morphological differences other than biometrics (see diagnoses), which lead us to conclude their distinctiveness.