 Akodon spegazzinii is medium in size for the A. boliviensis species group . The coloration of its upperparts varies considerably , from light to dark and from yellowish to reddish brown . The underparts are yellow @-@ brown to gray . The eyes are surrounded by a ring of yellow fur . The skull contains an hourglass @-@ shaped interorbital region ( between the eyes ) and various features of the skull distinguish the species from its close allies . Head and body length is 93 to 196 mm ( 3 @.@ 7 to 7 @.@ 7 in ) and body mass is 13 @.@ 0 to 38 @.@ 0 g ( 0 @.@ 46 to 1 @.@ 34 oz ) . A. spegazzinii has 40 chromosomes . 
