From 12 to One Species: Variation in Lobocheilos rhabdoura (Fowler, 1934) (Cyprinidae: Labeonini)

The cyprinid genus Lobocheilos in mainland Southeast Asia has a complex taxonomic history, with 12 nominal species described in the early- to mid-20^th Century from Thailand, Laos, and Vietnam by several authors based primarily on lateral melanin pigmentation and morphometric data. More recent works tentatively recognize anywhere from two to six valid species in the region. The goal of this study was to examine morphological variation between these putative species to determine if they represent distinct species. Examinations of 445 specimens, including all available type material, from throughout the region failed to define morphologically distinct groups or any differences between allopatric populations in the major zoogeographic regions in the area. Furthermore, an ontogenetic pattern of lateral melanin pigmentation was identified that has likely contributed to taxonomic confusion. One species is recognized from this region, with the oldest available name being L. rhabdoura (Fowler, 1934). Lobocheilos rhabdoura is herein redescribed, and phylogenetic relationships of populations throughout the region are reconstructed.