“…The studied specimen was caught at Cerro Colorado (Figure 1 To date, most of the records for sigmodontine rodents in the Chaco are restricted to Humid Chaco ecoregion, in the central Paraguay and the eastern portion of the Argentinian provinces of Chaco and Formosa (e.g. Shamel 1931, Gyldenstolpe 1932, Massoia 1971, 1973, 1976, Contreras 1982, Heinonen Fortabat 2001, D'Elía and Pardiñas 2004, Pardiñas and Ramírez-Llorens 2005, Pardiñas and Teta 2005, D'Elía et al 2008. Some contributions have summarized the few records from the western Arid Chaco areas in Argentina, including the provinces of Catamarca (Mares et al 1997), Salta (Díaz et al 2000, Gómez et al 2012, Jujuy (Díaz and Barquez 2007), Tucumán (Gómez et al 2012) and Santiago del Estero (Gómez et al 2012, Nanni et al 2012.…”