Diagnostic features. Solanum perarmatum is distinctive by virtue of its prostrate habit, entire ovate leaves, and abundant long prickles on the stems and calyx. It is easily distinguished from all associated Solanum species except S. cleistogamum Symon. S. perarmatum and S. cleistogamum are very similar, but the corolla of S. cleistogamum is 6–9 mm long (vs. 13–16 mm long for S. perarmatum), and its fruits are 9–12 mm diameter at maturity (vs. 18–22 mm diameter for S. perarmatum).

Distribution. Solanum perarmatum is endemic to Western Australia, and is almost confined to the Pilbara bioregion, extending from the coast to about 400 km inland.

Etymology. The epithet is derived from the Latin perarmatus, meaning ‘very thorny, heavily armed’.

Notes. The type of Solanum horridum Dunal was collected during the Baudin expedition, presumably in July or August of 1801, when the crew of the Géographe mapped the coastline north from Shark Bay en route to Timor.