 "Lundomys molitor" is among the largest living oryzomyines, rivaled only by some large forms of "Holochilus" and "Nectomys", but it is substantially smaller than some of the recently extinct Antillean species, such as ""Ekbletomys hypenemus"" and "Megalomys desmarestii".Unlike in "Holochilus brasiliensis", which occurs in the same area, the tail is longer than the head and body.It is sparsely haired and dark, and there is no difference in color between the upper and lower side.