All representatives of the genus Ilyocryptus with short lateral setae at the postanal margin of the postabdomen may be separated into the compact species group I. brevidentatus s. lat. A new species of Ilyocryptus from this group is described from the Lake Numalla, Queensland, Australia. I. smirnovi n. sp. shows clear morphological differences in the armature of the valve, postabdomen, and several other structures, from all other species of the group. Differences between members of the above-mentioned species group are analogous with those between European species, listed by Štifter (1991).