A Map covering the Oriental biogeographic region and showing the distribution of localities (black and red circles) of specimens of Notopterus examined in this study. Black star indicates the estimated type locality of Notopterus notopterus in Java (i.e. Jakarta region) and red stars indicate the likely origin localities of the two syntypes of Notopterus synurus (i.e. coast of Malabar and Coromandel coast at Tharangambadi [formerly Tranquebar]). Main Oriental river basins from West to East: 1. Indus basin; 2. Ganga-Brahmaputra river system; 3. Irrawaddy basin; 4. Salween basin, 5. Mekong basin. Insert shows the left lateral view of a specimen of Notopterus notopterus (Penang State, west Peninsular Malaysia; 20 cm in standard length, voucher specimen number USMFC (3) 00002, NO_1). B The unrooted network constructed with the software PopArt and a median-joining algorithm showing the COI haplotype relationships within the genus Notopterus. Branch lengths are not proportional to the number of changes. Red circles indicated haplotypes of Notopterus synurus (South Asia) and black circles indicated haplotypes of Notopterus notopterus (Southeast Asia).