The central thallus area is characterised by irregularly shaped, convex areoles ranging from 0.3 to 0.8 mm in width, forming a verrucose or papillose texture.

[3] Filsoniana australiensis shares some resemblance with the Asian species Caloplaca scrobiculata in terms of its overall appearance and dull colouration.

It can be distinguished by its eroded (scrobiculate) surface texture and a brighter thallus hue, which is attributed to the exposure of its white medullary layer.

Unlike C. scrobiculata, F. australiensis lacks marginal lobes and has a different type of ascospores, along with a distinct geographical distribution.

While these species share similar palisade inclusions in the cortical layer, F. australiensis sets itself apart with its almost rounded hyphal cells and unusually wide lumina measuring 4–5 μm.

[3] Filsoniana australiensis is typically found on various rock types including granite, quartzite, basalt, sandstone, and schist, preferring sun-exposed locations.