Caenocentron Schmid, 1982 is a small net-tube caddisfly genus distributed in the southern Nearctic and Neotropical regions. Two species were previously recorded in Mexico: Caenocentron trilineatum (Mosely 1934) and Caenocentron ideolus Schmid, 1982. In this study, Caenocentron chinantecum Razo-González and Vilarino, sp. nov. is described from Oaxaca, Mexico, which is similar to C. carlosdelarosai Vilarino, Dias and Bispo, 2022 from Costa Rica, with main differences observed in the shape of inferior appendage, position of its spine, and the paraproct lateral spine-like setae and asymmetrical dorsal processes. COI barcode of the new species and congeners was compared and the intra and interspecific distances were assessed. Minimum interspecific differences in the genus were around 5%, which may serve as a threshold for species delimitation. ASAP, PTP, TCS, and ABGD species delimitation models were used, but only the last one was congruent with morphological species criteria. Maximum likelihood analysis placed the new species closely related to C. carlosdelarosai. The haplotype structure of the species showed 26 haplotypes. Caenocentron carlosdelarosai showed eight haplotypes, clustering in two main groups with a high genetic distance (4.6%) but without morphological differences. An updated identification key for Caenocentron species is provided.
