Amolops caelumnoctis Rao & Wilkinson, 2007, a Junior Synonym of A. splendissimus Orlov & Ho, 2007 (Amphibia: Anura: Ranidae)

Amolops splendissimus Orlov and Ho, 2007 and A. caelumnoctis Rao and Wilkinson, 2007 were described almost simultaneously from either side of the China-Vietnam border. The two species share a strong morphological resemblance, and their taxonomic distinctiveness has been questioned, yet no one has confirmed the taxonomic relationship and status between the two taxa. To resolve this taxonomic issue, we collected additional topotypic and near-topotypic specimens of A. splendissimus and A. caelumnoctis from both China (A. caelumnoctis: Wenshan County, Yunnan Province; type locality Luchun County, Yunnan Province), and Vietnam (A. splendissimus: Tam Duong District, Lai Chau Province; type locality Mount Ky Quan San, Bat Xat, Lao Cai Province). Molecular analysis based on a 16S rRNA fragment revealed minimal genetic divergences between the two taxa (0.0%-0.4% uncorrected p-distance), and both species are closely related to A. viridimaculatus (2.1%-2.3%) and A. medogensis (3.5%-3.7%). Morphological comparisons between the newly collected specimens and the original descriptions of both species further support the lack of distinctiveness of the two species, hence, we conclude that A. caelumnoctis is a junior synonym of A. splendissimus.