Résumé
The caviomorph rodent diversity of the Solimões Formation (Upper Miocene, Brazil) has revealed remarkable taxonomic richness, offering key insights into the evolutionary history of Amazonian biodiversity. However, small caviomorphs, which are likely the most diverse within the clade, remain poorly known, largely due to recovery challenges. This study describes new dental remains of small-sized caviomorphs from the “Coqueiros” fossil-bearing locality (Envira River, Acre, Brazil), obtained by wet-screening of the sediments process. The material comprises three new species of Erethizontoidea, assigned to two genera. Micronoamys gen. nov., represented by M. candelae sp. nov., is the smallest known Miocene erethizontoid and shows high-crowned molars, unilateral hypsodonty, a short oblique hypoflexus and a posteroloph initially disconnected from the hypocone area. Enviramys gen. nov., with E. vucetichae sp. nov. and E. nasifae sp. nov., exhibits small size, brachydonty, and elongated crests and flexi. Additional remains of cf. Microscleromys sp. and cf. ‘Scleromys’ sp. were also identified. Computed tomography (CT) was used to evaluate tooth wear patterns and visualize morphological features, allowing for comparisons between wear stages. The presence of small, presumably arboreal erethizontoids suggests forested habitats, consistent with other Miocene sites in Western Amazonia. These findings expand our knowledge of the Miocene rodent diversity in South America, especially in Proto-Amazonia. They also highlight biogeographic connections between Western Amazonian and adjacent Miocene faunas. The discovery of these small-sized rodents emphasizes the importance of wet screening of fossil-bearing sediments in recovering poorly represented taxa and contributes to refining our knowledge of mammalian evolution and biogeography in the Amazonian region.