Monodilepas diemenensis was originally discovered and described by Harold John Finlay in 1930.

[1] Finlay's original text (the type description) reads as follows: Monodilepas diemenensis n. sp.

Sculpture is coarser, like otagoensis, shape a cross between monilifera and skinneri Finlay, not so high as the former, not so elongate and parallel-sided as the latter, which is from the Chatham Islands (Trans.

Distinguishable at sight from all the other species by the characters of the hinder margin and foramen; the hinder margin instead of being in the plane of the others is considerably raised off the ground, leaving a wide gape; the foramen is larger and more elongate than in monilifera, almost equalling skinneri in this feature, and especially has a quite different internal callus; this is hexagon-shaped instead of subtriangular, the posterior margin being strongly angled.

There are apparently no previous records of the genus from the North Island.This article incorporates public domain text coming from New Zealand from the reference.