The Eastern puna mouse is a large, stout mouse with long dark-brown fur on the top of the body and gray fur on the bottom of the body. Aside from that, no specimens have been collected since 1970. Within Peru, it is found in moist areas within
puna grassland at elevations of to in the
Kallawaya mountain range, a section of the
Cordillera Oriental. This is provisionally the third-highest known range of any species of mammal, after the
Punta de Vacas leaf-eared mouse and
P. lemminus. One specimen, found in 2023, extended the range of
Punomys to . It was provisionally assigned to
P. lemminus, but the authors were not certain of its identification between that and
P. kofordi; if it were re-identified as
P. kofordi, then it would have the second-highest known range instead of
P. lemminus. The Eastern puna mouse's habitat is differentiated from
P. lemminus by higher annual rainfall. They were often found near
Senecio bushes. Several Eastern puna mice may share a burrow. While there is limited data, they likely breed during the summer wet season, with litters of two to three. ==References==