A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes Moreira, Camila Do Nascimento Ventura, Karen Percequillo, Alexandre Reis Yonenaga-Yassuda, Yatiyo Zootaxa 2020 2020-11-06 4876 1 1 111 3D5RD Thomas 1884 [151,394,907,933] Mammalia Cricetidae Euryoryzomys GBIF Animalia Rodentia 15 16 Chordata species nitidus  Karyotype: 2n = 80 and FN = 86. Autosomal complement: four small metacentric pairs, and 35 acrocentric pairs (one distinctly large and the remaining large to small decreasing in size). Sex chromosomes: X, a very large subtelocentric; Y, a small acrocentric ( Gardner & Patton 1976, pp. 4, Fig. 1E; Patton et al. 2000). A different morphology of sex chromosomes was reported by Volobouev & Aniskin (2000), a submetacentric X and a metacentric Y chromosome. C-banding metaphases exhibited blocks of constitutive heterochromatin on the pericentromeric region of all autosomes. The short arm of X and the Y were entirely heterochromatic. G-banding was also performed ( Volobouev & Aniskin 2000). FISH with telomeric sequences revealed signals exclusively at the ends of all chromosome arms and no interstitial signals were observed ( Silva et al. 2000).