Oligoryzomys fulvescens Karyotype: 2n = 60 and FN = 74. Autosomal complement: six metacentric and submetacentric pairs (two large, two medium, and two small), three large subtelocentric pairs, and 21 acrocentric pairs medium to small decreasing in size. Sex chromosomes: X chromosome presented two different morphologies, a large subtelocentric, and a large acrocentric; Y, a small acrocentric (Haiduk et al. 1979, pp. 611, Fig. 2A).

Published as part of Moreira, Camila Do Nascimento, Ventura, Karen, Percequillo, Alexandre Reis & Yonenaga-Yassuda, Yatiyo, 2020, A review on the cytogenetics of the tribe Oryzomyini (Rodentia: Cricetidae: Sigmodontinae), with the description of new karyotypes, pp. 1-111 in Zootaxa 4876 (1) on page 62, DOI: 10.11646/zootaxa.4876.1.1, http://zenodo.org/record/4423612