Epopostruma topendi

Epopostruma topendi is a rare species currently known from two single specimens collected in different remote regions in the Top End of the Northern Territory. Both were collected in pitfall traps set in savanna woodlands.

Identification
This species lacks lateral expansions of the postpetiole, and so belong to the E. quadrispinosa group (Shattuck 2000). The presence of pronounced posterolateral but not anterolateral teeth on the postpetiole, along with an entirely smooth gaster, indicates that it is closely allied to Epopostruma areosylva from New South Wales and southeastern Queensland, from which it is readily distinguished by its generally smooth appearance (especially dorsally) and dentate rather than spinose petiole. The only representatives of Epopostruma previously known from far northern Australia are Epopostruma quadrispinosa and Epopostruma monstrosa, both occurring in the wet tropics of North Queensland (Shattuck 2000). They are readily distinguished from E. topendi by their coarser sculpture, lack of posterolateral teeth on the postpetiole, and presence of gastric sculpture.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Nomenclature

 * . Epopostruma topendi Pettit & Andersen, 2021: 142 (w.), figs. 1a-d, AUSTRALIA (Northern Territory).

Taxonomic Notes
Although both known specimens of this species are extremely similar, they have notable differences in the structure of the petiole and postpetiole. In the holotype from Nitmiluk National Park, the petiole is rectangular in dorsal view and the anterior corners are conspicuously dentate (Fig. 2a). In the Melville Island specimen, the petiole is broader and dome-shaped anteriorly and has very small and inconspicuous denticles (Fig. 2b). Furthermore, in the Melville Island specimen the anterolateral corners of the postpetiole are more rounded, and the posterolateral teeth are narrower. We have conservatively described the two specimens as conspecific due to a lack of additional collections and therefore information on intraspecific variation. However, they possibly represent different species and were considered as such in Andersen et al. (2018).

Description
Holotype worker. TL 3.9; HL 0.81; HW 0.75; CI 93; ML 0.43; MI 53; SL 0.49; SI 65; PW 0.51 AL 1.01. In full-face view the lateral margin of the head between the eye and the occipital lobe slightly angular. Posterior margin of head deeply concave, with occipital lobes somewhat angled posteriorly. Pronotal spines present, elongate. Posterior section of mesonotum in approximately the same plane as the dorsal face of propodeum, the junction of these plates forming a very shallow depression. Posterior face of propodeum with thin flanges between bases of spines and propodeal lobes. Petiolar node with a pair of conspicuous, semi-erect denticles on the dorsolateral margins. In dorsal view, petiolar node narrow and parallel-sided. Anterior face of the postpetiole distinctively flattened, with angular lateral margins. Sides of postpetiole not expanded laterally. In dorsal view, postpetiole bluntly square anterolaterally and conspicuously dentate posterolaterally, with denticles broader than long. Dorsum of petiole, postpetiole and gaster with numerous short, blunt and often clubbed erect hairs. Head, mesosoma, petiole and postpetiole with well-spaced foveolae and to a large extent smooth and shiny, especially dorsally. First gastral tergite entirely smooth. Colour uniformly reddish-brown.