Small mammals from the Seasonally Dry Tropical Forests of the Huallaga river basin and new records for San Martín department, Peru Author Ruelas, Dennisse Author Pacheco, Victor text Check List 2021 2021-06-07 17 3 877 894 http://dx.doi.org/10.15560/17.3.877 journal article 10.15560/17.3.877 1809-127X Marmosa constantiae (Thomas, 1904) Figure 3A Material examined. PERU • Valle del Biavo private conservation area, Bellavista Province ; 07°11′54″S , 076° 33′38″W ; 348 m elevation; 24–25.VIII.2015 ; D. Ru- elas leg.; snap-trap; 1 ♀ ( MUSM 43888 , 43890 ) and 2 ♂ ( MUSM 43889 , 43891 ); all adults . Identification. The following combination of morphological characters allows us to recognize this large mouse opossum: drab, woolly dorsal fur; not a well-defined facial mask; yellowish-buffy cheeks; light dorsal fur washed with orange on the body sides; yellowishcream to yellowish buffy ventral fur; two-thirds of the distal portion in ventral view slightly depigmented; long, all-dark tail with rhomboidal scales arranged in spiral series; laterally and dorsally projected supraorbital ridges; developed postorbital processes, well-developed in most mature adults; almost completely ossified pal- ates with short-narrow maxillopalatine openings; moder- ately convergent temporal ridges shaping a sagittal crest; and small auditory bullae. External and craniodental measurements are given in Table 3 . Morphological characters and measurements of our specimens are within the variation range for the species following Lima Silva et al. (2019) and Voss et al. (2019) and in specimens in the MUSM collection ( Ucayali Department: MUSM 44233– 44237, 44240–44243). Remarks. Recently Lima Silva et al. (2019) and Voss et al. (2019) recognized constantiae as the valid name for specimens previously known as demararae in Peru . Marmosa constantiae has a wide distribution in southwestern Amazonia, including western Brazil , eastern Peru , and northern Bolivia ( Lima Silva et al. 2019 ). In Peru , this species is distributed in the Yungas and Selva Baja ecoregions ( Pacheco et al. 2009 ).