Nectomys magdalenae (= N. m. grandis)

Karyotype: 2n = 34 and FN = 40. Autosomal complement: one large metacentric pair, three large submetacentric pairs, and 12 acrocentric pairs (two medium and the remaining small). Sex chromosomes: X, a medium acrocentric; Y, a small submetacentric (Gómez-Laverde et al. 1999, pp. 663, Fig. 1). Another diploid number of 32 was mentioned by Bonvicino & Weksler (2015) as unpublished data obtained by M. L. Bueno.