Ralf Britz & Maurice Kottelat

Abstract. Mastacembelus dictyon, new species, a spiny eel of the M. armatus species group, is described from the Mekong drainage in Laos. It is distinguished from M. armatus by having fewer caudal-fin rays (13–15 vs 18–20), fewer abdominal (35–39 vs 42–43), caudal (47–51 vs 51–55), and total vertebrae (85–90 vs 94–97), and by fewer dorsal-fin spines (33–37 vs 37–38); and from M. favus by differences in colour pattern. Earlier records of M. favus from Laos are not confirmed, but its presence there is possible; a lectotype is designated for M. favus. A neotype is designated for M. armatus; its type locality is in the Ganges drainage, India. Previous neotype designations for M. undulatus and M. thacbaensis are invalid. A neotype is designated for M. undulatus, making it an objective junior synonym of M. armatus. The presence in Laos of M. dienbienensis, M. thacbaensis, and M. tinwini is confirmed.

Key words. Mastacembelidae, Mastacembelus armatus group, Mekong basin, lectotype, neotype

Read article here: RBZ-2025-0042