One extant species, Leptomyrmex relictus, is known from central Brazil;[3] otherwise, the global distribution of this genus is restricted to eastern Australia, New Caledonia and New Guinea, as well as the nearby Indonesian islands of Aru and Seram.

[5] Workers of Leptomyrmex can be easily recognized by elongate antennal scapes which surpass the posterior margin of the head by more than one half their length, a medially notched hypostoma, mandibles with 7–15 teeth and 5–12 denticles, and a laterally located anterior tentorial pit.

All six species are readily distinguished from their larger congeners by their small size (head width < 0.80mm), brown coloration, relatively short dorsal face of the propodeum, angular (not rounded) petiole and gaster lacking lateral compression.

These observations, in addition to the fact that the sister group of Leptomyrmex (i.e., (Forelius + Dorymyrmex)) also has winged queens, may help explain the proposed widespread former distribution.

On the other hand, a recent molecular phylogenetic analysis of the Dolichoderinae places Leptomyrmex firmly within a clade of species (tribe Leptomyrmecini) whose origins appears to be in the Neotropics, with two main dispersal events to Australia.