A new species and first record of the genus Procerobaetis Kaltenbach & Gattolliat, 2020 (Ephemeroptera, Baetidae) from Thailand.

The genus Procerobaetis Kaltenbach & Gattolliat, 2020 is reported for the first time from Thailand, and Procerobaetis totuspinosus sp. nov. is described as a new species based on larvae. It can be easily distinguished from other known Procerobaetis species by the presence of triangular spines at the posterior margin of tergites VI-IX. COI sequences were obtained from all known species. The genetic distances (Kimura 2-parameter) between the new species and the other species are between 20% and 23%. The morphological characters of the new species and its closely related species are discussed; larval key to all species of the genus Procerobaetis is also provided.