Microryzomys altissimus (Osgood, 1933)

Lee Jr, Thomas E., Tinoco, Nicolas, Crockett, Seth C., Camacho, M. Alejandra & Burneo, Santiago F., 2021, Report on the mammals of Quimsacocha National Recreation Area, Azuay Province, Ecuador, Check List 17 (1), pp. 125-131 : 128

Microryzomys altissimus (Osgood, 1933)

Material captured. Four females and 19 males ( QCAZ 17907–17919), measurements (in mm): total 174–202, ear 13–17, foot 19–25; 03°03′43″S, 079°13′54″W; 3,860 – 3,760 m; 26, 31 July; 2–5, 7 August 2018; collectors: Lee, Tinoco and Crockett. These specimens were collected in herbaceous paramo stream and patch forest in Sherman traps.

Identification. These specimens are brownish dorsally with a grayish grizzled head ( Fig. 2E). The tail is bicolored and less than 142 percent of head and body length, that is indicative of M. altissimus (Carleton and Musser 1989) . The hands and feet are whitish. The incisor tubercle on the dentary is short and indistinct and the length of maxillary toothrow is greater than 3 mm. The incisive foramina are long, penetrating M1 ( Carleton 2015). Microryzomys minutus has a unicolored tail greater than 145 percent of head and body length. The incisor tubercle on the dentary is distinct and large, the length of maxillary toothrow is less than 3 mm, and the incisive foramina do not penetrate M1.