Oligoryzomys magellanicus

Karyotype: 2n = 54 and FN = 66. Autosomal complement: seven metacentric and submetacentric pairs (one very large and the remaining small), and 19 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X, a medium submetacentric; Y, a small submetacentric (Gallardo & Patterson 1985, pp. 53, Fig. 2).