 The morphology of the upper and lower jaw precludes an identification as "Holochilus primigenus", a fossil species with molar traits almost identical to those of "Lundomys".The length of the upper toothrow of one specimen from this locality is and the length of the upper first molar is , slightly smaller than in living "Lundomys", which ranges from in four specimens

"Lundomys molitor" is semiaquatic in habits, spending much of its time in the water, and is active during the night.An excellent swimmer, it is even more specialized for swimming than is "Holochilus".