A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes Author Moreira, Camila Do Nascimento Author Ventura, Karen Author Percequillo, Alexandre Reis 0000-0001-9490-5457 cmoreirabio@gmail.com Author Yonenaga-Yassuda, Yatiyo text Zootaxa 2020 2020-11-06 4876 1 1 111 journal article 7983 10.11646/zootaxa.4876.1.1 4ee8b608-7c73-4980-9e86-3e3719e91c7f 1175-5326 4423612 190EC586-E14B-4AEF-A5EF-3DA401656159 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 ).