Sigmodontine rodent diversity: The Frankenstein paradox

Thomasomys, primarily Andean cricetid rodents, represents the most speciose genus in the subfamily Sigmodontinae, with 53 described species and estimates suggesting nearly 100. Its remarkable diversity contrasts with the taxonomic asymmetry of Sigmodontinae, where most genera have fewer than five species. While debates on splitting Thomasomys persist, its internal disparity—spanning morphology, genetics, and ecology—challenges traditional genus definitions. Elevating species groups to generic rank could reframe Thomasomyini as a genus-rich tribe, paralleling Phyllotini. This debate highlights broader questions about genus cohesion, biodiversity representation, and the integrity of taxonomic frameworks in evolutionary biology.