Diagnostic features. Hibbertia aurea can be distinguished from all other species in the H. aurea-H. crassifolia group by the combination of glabrous leaves (10–)15–30(–55) mm long that taper to a sharply acute apex, and 6–8 ovate-acuminate, glabrous floral bracts (5.5–)7–9 mm long, which, like the sepals, are distinctly chartaceous, glossy, firm-textured and rather rigid especially towards the apex, where they are often distinctly keeled.

Phenology. Flowers between late July and early November, with a peak in September.

Distribution & habitat. Occurs on the Darling Range east of Perth, from Walyunga and Red Hill south to Karragullen and Ellis Brook (Fig. 1), in or adjacent to jarrah-marri forests and woodlands with shrubby understoreys, in often stony, clayey, lateritic soils over granite (often around granite outcrops). One of the specimens cited (PERTH 3097854) has the recorded locality "Cannington"; this is on the Swan Coastal Plain, and is likely to be in error, as the species is not known west of the Darling Scarp.

Conservation status. Common, including in conservation reserves within its area of distribution, and not considered to be at risk.

Notes. Hibbertia aurea, as circumscribed prior to this paper, was regarded as widespread, occurring from near Eneabba south to the Blackwood River. However, its circumscription and geographic range are greatly reduced here, mainly through the segregation of the more widespread H. pallida. The latter differs in being generally smaller, less erect plants that are multi-stemmed at base and probably resprout after fire (H. aurea is taller and likely reseeds after fire), with smaller, less acute leaves, and floral bracts and sepals that have a herbaceous rather than chartaceous texture and lack the rather rigid, keeled apices of H. aurea. In the field, the petals of H. aurea are distinctly rich, golden-yellow, while those of H. pallida (as Steudel's name for the latter suggests) are paler and less richly coloured. This difference, however, is subtle. Plants of H. aurea are usually more floriferous than those of H. pallida. The two species do not co-occur; in the vicinity of Perth, H. pallida is common on the Swan Coastal Plain including on acid sandy soils under Banksia woodland, and does not extend to the Darling Range where H. aurea occurs; conversely, H. aurea does not extend onto the coastal plain.

Wheeler (1987) noted that there were 'variants' of her broadly circumscribed H. aurea. These probably comprise specimens of H. pallida and H. lesueurensis.

Hibbertia aurea is unusual amongst Western Australian ericoid-leaved Hibbertia in that the abaxial leaf surface varies from quite smooth to distinctly papillate, with intermediates between these end-points. In other species and species groups, the distinction between smooth and papillate abaxial leaf surfaces (including between smooth and papillate edges to the abaxial midrib) is species-diagnostic. Hibbertia aurea is currently the only known case where this character, which presumably has great significance for ecophysiology and water relations, is variable.

Typification. The M and MEL syntypes do not have a b designation, the latter bearing a label in Steudel's hand '24. Hibbertia aurea Steudel! (non H. pallida Steudel)'. They clearly match H aurea.