Redescription of the Types of Ischikauia macrolepis Regan, 1908, an Extinct Cyprinid (Teleostei: Cyprinidae) from Taiwan and the Replacement in the Genus, Rasborinus Oshima, 1920

In an early freshwater fish survey, Regan (1908a, b) described several species of freshwater fishes from Taiwan after Gunther’s exploration. Although some of these should be regarded as synonyms or endemic species of Taiwan (Chen and Yu 1986, Tzeng 1986, Shen and Tzeng 1993), Taiwanese ichthyologists have had no chance to examine most of types since publication of those endemic freshwater fishes. As example, Ischikauia macrolepis, was described as collected from Kagi (Chiayi), southwestern Taiwan by Regan, and since WWII has been no any further record. Chen and Yu (1986) merely kept this record, based on the original description, but there were no available specimens. Later, Shen and Tzeng (1993) excluded the record from the family Cyprinidae in Fishes of Taiwan. More recently, it has been considered that it should be grouped into the genus, Hemiculter, and probably as the junior synonym of H. kneri Kreyenberg (Tzeng 1996). However, the taxonomic status of this species is doubtful if based on the limited description of features from Regan, and this problem has never been resolved until the present study of examined the types. It seems necessary to resolve several problems of synonymy of freshwater fishes of Taiwan by examining the original types held at the British Museum. Fortunately in the British Museum there are 3 syntypes of I. macrolepis which can be located. After re-examination of the types by one of us (ISC), we concluded that this species should be grouped in the genus Rasborinus Oshima, 1920, but not the genus Hemiculter as recently suggested by Tzeng (1996), nor to Ischikauia. The species I. macrolepis agrees well with the detailed original description, as well as from a re-examination of the type species of Rasborinus, R. takakii Oshima except for the anal ray count in the original description (Oshima 1920). R. takakii is an apparently extinct, small endemic cyprinid from Taiwan which has never been formally collected since the description by Oshima. However, R. takakii has been treated as a junior synonym of R. lineatus which was originally described as Ischikauia lineatus Pellegrin, 1907, and this species was found