Pareuchiloglanis

Xu Li, Wei Zhou, Alfred W. Thomson, Qing Zhang & Ying Yang, 2007, A review of the genus Pareuchiloglanis (Sisoridae) from the Lancangjiang (upper Mekong River) with descriptions of two new species from Yunnan, China., Zootaxa 1440, pp. 1-19 : 17-18

Key to the species of Pareuchiloglanis in the Lancangjiang, China

1 Premaxillary tooth patches appear joined, with shallow median indentation (Fig. 2A); no sulcus between maxillary barbel and lower lip (Fig. 3A) .................................................................................................... 2

- Premaxillary tooth patches separate (Fig. 2B); sulcus present between maxillary barbel and lower lip (Fig. 3B) ................................................................................................................. Pareuchiloglanis kamengensis

2 Origin of anal fin posterior, inserted nearer to caudal-fin base than to end of pelvic-fin base; tip of dorsal fin not reaching origin of adipose fin when depressed; pectoral fin not reaching origin of pelvic fin; pelvic fin not reaching or only reaching anus .......................................................................................................3

- Origin of anal fin anterior, distance to caudal-fin base longer than to pelvic-fin origin; tip of dorsal fin reaching origin of adipose fin when depressed; pectoral fin extending beyond origin of pelvic fin; pelvic fin extending beyond anus............................................................................. Pareuchiloglanis abbreviatus

3 Branched rays of caudal fin 7+8; anus midway between posterior end of pelvic-fin base and anal-fin origin or nearer to anal-fin origin.................................................................................................................... 4

- Branched rays of caudal fin 6+7; anus nearer to posterior end of pelvic-fin base than to anal-fin origin ... .................................................................................................................... Pareuchiloglanis prolixdorsalis

4 Caudal peduncle slender, depth 16.6-30.1% in length; pelvic fin reaching anus; anus located midway between end of pelvic-fin base and anal-fin origin.................................. Pareuchiloglanis gracilicaudata

- Caudal peduncle deeper, depth 30.3% in length; pelvic fin not reaching anus; anus nearer to anal-fin origin than to posterior end of pelvic-fin base.................................................... Pareuchiloglanis myzostoma

Discussion

The morphology of the premaxillary tooth patches is considered to be a chief character for identifying genera in the tribe Glyptosternina (Chu 1979, 1981; Thomson & Page 2006), and as a character in elucidating the phylogeny of Glyptosternina (He 1995b, 1996). Dissection of the skeleton shows that the premaxillary tooth band of Pareuchiloglanis is separated into two patches (He 1996). We divide the premaxillary tooth band of Pareuchiloglanis into two types. In one type the premaxillary tooth patches appear separate, medially divided by a deeper indentation. This type is characteristic of P. kamengensis , P. feae , P. macropterus and P. gongshanensis . This group is distributed in and to the west of the Lancangjiang (Fig. 4) and overlaps that of Oreoglanis , Pseudexostoma and Exostoma (Chu et al. 1990; Ng & Rainboth 2001; Ng 2004). In the other type, the premaxillary tooth patches appear to be joined with a shallow medial indentation. This type is characteristic of all other species of Pareuchiloglanis . This group is distributed in and to the east of the Lancangjiang(Thomson & Page 2006).

In the first group, the morphology of the premaxillary tooth patches is more similar to that of Oreoglanis species. These species of Pareuchiloglanis also have a sulcus between the maxillary barbel and the lower lip, and the lower lip is not connected to the base of the maxillary barbel. This characteristic is also similar to that of Oreoglanis species(Fig. 3). Based on morphology and geographic distribution, the authors consider P. kamengensis , P. feae , P. macropterus and P. gongshanensis to form a monophyletic group that may be a transitional group from Pareuchiloglanis to Oreoglanis . This group is distributed extensively in the Lancangjiang, Nujiang, Irrawaddy and Brahmaputra river systems, which implies that rivers in this area could have been historically connected with each other.