Found at night at eye level in lowland terra firme forest. I consulted Rob Voss (AMNH) and he thought it could be Gracilinanus emiliae, which “would be a significant range extension, but perhaps not a very surprising one” (there are records from Meta, Colombia and Loreto, Peru - see Voss et al. 2009 at https://mn.sarem.org.ar/article/on-the-diagnostic-characters-ecogeographic-distribution-and-phylogenetic-relationships-of-gracilinanus-emiliae/). Manus appears to be paraxonic (hand digit V being nearly as long as digit IV) which agrees with Gracilinanus and Marmosa (see Table 2 and Fig. 3 in Voss et al. 2004 at https://digitallibrary.amnh.org/handle/2246/2776). G. emiliae differs from congeners in its white ventral pelage (gray/brown in the remaining species) according to Voss et al. 2009 (op. cit.).