Oligoryzomys yatesi

Karyotype: 2n = 54 and FN = 66. Autosomal complement: seven biarmed pairs (one very large and the remaining small), and 19 acrocentric pairs decreasing in size. Sex chromosomes: X and Y were subtelocentrics (Palma & Rodríguez-Serrano 2017, pp. 6, Fig. 2A). According to the authors, this karyotype was very similar with the karyotype of O. magellanicus reported by Gallardo & Peterson (1985).

The karyotype of two more undescribed species were reported by Gardner & Patton (1976) and Andrades-Miranda et al. (2001a).