Microryzomys altissimus (Osgood)

VOSS, ROBERT S., 2003, A New Species of Thomasomys (Rodentia: Muridae) from Eastern Ecuador, with Remarks on Mammalian Diversity and Biogeography in the Cordillera Oriental, American Museum Novitates 3421, pp. 1-48 : 23

Microryzomys altissimus (Osgood)

SPECIMENS COLLECTED: 10.6 km (by road) W Papallacta, 12,600 ft (UMMZ 155799); 8.9 km (by road) W Papallacta, 12,480 ft (AMNH 248497); 8.2 km (by road) W Papallacta, 12,200 ft (UMMZ 155677); 7.5 km (by road) W Papallacta, 12,000 ft (UMMZ 155672–155676, 155802); 6.9 km (by road) W Papallacta, 12,020 ft (AMNH 248279, 248280); 6.2 km (by road) W Papallacta, 11,700 ft (UMMZ 155798); near Papallacta, 10,480 ft (UMMZ 127125); 1.6 km (by road) E Papallacta, 10,250 ft (AMNH 248277).

OTHER MATERIAL: Three specimens collected by L. Söderström in 1913 and 1914 are labeled ‘‘ Papallacta 11,000 ft’’ ( AMNH 47068 , 47071 ) or ‘‘ Tambo above Papallacta 12,000 ft’’ ( AMNH 47069 ). Four others ( AMNH 66577–66580 ) were collected by G.H.H. Tate in 1923 on Cerro Antisana at 13,500–13,600 ft [4116–4146 m] .

TAXONOMY: The genus Microryzomys was revised by Carleton and Musser (1989), who provided morphological diagnoses of both currently recognized species based in part on the material listed above and below.

FIELD OBSERVATIONS: The 14 specimens of Microryzomys altissimus that I collected near Papallacta in 1978 and 1980 were trapped at elevations ranging from 3124 to 3840 m. Of these, five were taken in the shrubby páramo/ forest ecotone, four in grassy páramo, and three in Subalpine Rain Forest; two captures in anthropogenic habitats (secondary vegetation surrounded by cow pastures) were the only ones below 3600 m. All recorded captures were in traps set on the ground, five of which were placed along the margins of small streams; of the remaining nine captures (away from streams), six were in runways under tall bunch grass and/or low shrubs mixed with grass, two were in relatively open sites without grass inside the forest, and one was under a mossy bank.