A new endemic genus of glass knifefish (Gymnotiformes: Sternopygidae) for the rare species Distocyclus guchereauae from the Maroni basin

Abstract A new genus is described for the rare species “Eigenmannia” guchereauae, originally described in Distocyclus but later transferred to Eigenmannia despite its morphology being incongruent with that genus. The description is based on recently collected material from the upper Tapanahony River in Suriname, part of the Maroni basin to which the species is endemic. Osteological and meristic features, together with multilocus phylogenetic analyses (COI, CytB, Rag1), support recognition of this lineage as distinct, and sister to Archolaemus. The new genus appears most morphologically similar to Archolaemus, but is distinguished chiefly by its lack of a free orbital margin. This recognition expands the number of sternopygid genera to eight and highlights the Guiana Shield as a center of gymnotiform endemism. Our findings underscore the importance of continued exploration of poorly studied regions such as the upper Tapanahony, which continues to reveal unexpected diversity and biogeographic complexity in Neotropical electric fishes.