Oligoryzomys sp.

Karyotype: 2n = 68 and FN = 74 or 76. Chromosome complement: one large subtelocentric pair, four metacentric and submetacentric pairs of small sized, and 29 acrocentric pairs large to small decreasing in size. The sex chromosome was unknown as only a female was examined (Gardner & Patton 1976, pp. 8, Fig. 3A).