Based on examination of the syntype female of Telagrion fulvellum which we designate as lectotype, and its comparison with additional male and female specimens from Peru, this species is assigned to a new genus, Dolonagrion, and both sexes are redescribed, diagnosed, and illustrated.
This synopsis of adult Triacanthagyna includes the revalidation of two species thought to be synonyms (T. nympha and T. obscuripennis), the description of a new species (T. williamsoni; type locality: Peru, Tingo María), keys to both sexes, illustrations of diagnostic characters, and distribution maps of all species. A phylogenetic assessment of the nine species is…