Oxymycterus wayku Jayat, D’Elía, Pardinãs, Miotti & Ortiz, 2008, a rodent species recently described, is known in only four localities within the Subtropical Mountain Forests of the Yungas eco-region in Tucumán, northwestern Argentina. Specimens were recorded in an owl pellet sample during a recent survey. This record represents the first for Oxymycterus in Catamarca Province, extending approximately 60 km south its southern distribution in the region. Sixteen other small non-volant mammal species were recorded there, turning this area into one of the most diverse for this understudied group in Argentina.