Microryzomys altissimus

Karyotype: 2n = 57 and FN = 58 (fundamental number comprises the number of autosomal and sex chromosomes arms). Chromosomal complement: 27 acrocentric pairs large to small decreasing in size, and three unpaired elements consisting of one large subtelocentric, one large acrocentric, and one small acrocentric. Sex chromosomes was unknown as only a female was examined. This individual was apparently a heterozygous for an autosomal Robertsonian translocation (Gardner & Patton 1976, pp. 10, Fig. 4A).