Oecomys franciscorum

Pardiñas et al. (2016) recognized the karyotype described by Andrade & Bonvicino (2003) for an undescribed species of Oecomys from Corumbá, Mato Grosso do Sul state of Brazil, as O. franciscorum . Karyotype: 2n = 72 and FN = 90. Autosomal complement: 10 biarmed pairs (one large and the remaining medium to small decreasing in size), and 25 acrocentric pairs large to small decreasing in size. Sex chromosomes: X, a submetacentric (the largest chromosome of the complement); Y, a medium submetacentric. One female presented heteromorphism of the short arm of the X chromosome. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of the majority of the autosome pairs. The X chromosome presented the short arm entirely heterochromatic, plus a C-band on the distal region of its long arm. The Y chromosome presented a heterochromatic block on the distal region of the long arm. G-banding was also performed (Andrade & Bonvicino 2003, pp. 198, Fig. 2A).