Australian Journal of
Taxonomy
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Type: Western Australia: Dragon Rocks Nature Reserve No. 36128. Southern section of the Reserve adjacent to the central fire break, 19 Sept. 1991, A.M. Coates 2875 (holo: PERTH 5154855, iso: CANB).
Hibbertia sp. Dragon Rocks (A.M. Coates 2875), Western Australian Herbarium.
Erect shrubs to 0.4 m high, single-stemmed at base and likely resprouting after fire. Young stems greyish-arachnose with minute, simple hairs. Leaves scattered, sessile, linear, 15–25 mm long, 1–1.5 mm wide, slightly dilated at the base especially near the flowers, greyish-arachnose like the stems when young, glabrescent (though with the indumentum persisting longer on the abaxial midrib); margins tightly recurved to the midrib and obscuring the abaxial lamina surface, which is greyish-pubescent on dissection; apex obtuse. Flowers single, terminating main stems and lateral short-shoots, sessile, sometimes in few-flowered clusters. Bracts 2–4; primary bract broadly ovate, acute, 4–5 mm long, herbaceous, densely pubescent abaxially with rusty simple hairs; secondary bracts grading into leaves. Sepals ovate to broadly triangular, c. 8 mm long, with abundant coarse, spreading, white, tubercle-based simple hairs overlying short, rusty simple hairs especially towards the apex; outer sepals acuminate; inner sepals broader and usually obtuse-apiculate, with membranous, minutely ciliolate margins. Petals 5, yellow, obovate, 9–10 mm long, emarginate. Stamens 20, in 5 bundles each of 4 stamens; filaments fused in the lower half, c. 1 mm long; anthers c. 1.8 mm long, narrowly oblong and dehiscing by introrse longitudinal slits; staminodes absent. Carpels 5; ovaries globular, glabrous; styles radiating outward, c. 1 mm long. Ovules 1 per carpel. Mature seeds not seen.
Diagnostic features. Hibbertia dracolithica can be distinguished from all other Western Australian taxa by the combination of linear leaves with the margins tightly recurved and abutting the midrib below; expanded, almost sheathing leaf bases especially close to the flowers; greyish-arachnose indumentum on stems and leaves when young (with the indumentum persistent on the abaxial midrib); sessile flowers with abundant spreading, white, tubercle-based hairs; stamens in 5 bundles united by their filaments; and 5 glabrous carpels.
Phenology. The type was collected flowering in September.
Distribution & habitat. Currently known only from a single location within Dragon Rocks Nature Reserve (Map 1), where it grows on the edge of a firebreak in open shrub-mallee with Eucalyptus albida, Melaleuca ?leptospermoides, Banksia sphaerocarpa, Beaufortia spp., Dryandra spp, Isopogon teretifolius, and Daviesia spp., on gravelly sandy soil.
Conservation status. Likely to be highly localised given the lack of other collections; the conservation status of H. dracolithica should be assessed through field surveys.
Etymology. From the Greek drakon (a dragon) and lithos (a stone or rock), in reference to the nature reserve from which the type specimen was collected.
Notes. Hibbertia dracolithica shares floral characters with H. glomerosa and is presumably closely related to it. It differs from that species in having linear leaves with the margins recurved to and tightly abutting the midrib (vs. oblong with ± flat margins so that the abaxial lamina is clearly visible, at least when fresh) and young leaves greyish-arachnose (vs. glabrous). The leaf indumentum is reminiscent of H. bistrata, but that species has flat leaves without strongly recurved margins, similar to H. glomerosa. In H. glomerosa and H. bistrata, specimens with relatively narrow leaves may dry with the margins somewhat recurved, but they are flat when fresh and the margins when dried do not tightly abut the midrib. The very narrow leaves of H. leptophylla dry with recurved margins, but these usually recurve to each other rather than tightly abutting the midrib, and are only slightly recurved when fresh.
In the type specimen, the stamens are consistently in bundles of four, giving a count of 20 stamens per flower. Hibbertia glomerosa, H. bistrata and H. leptophylla usually have more stamens per bundle. Further material is needed to determine whether this is a consistent difference.
At the type locality, a small number of plants were growing along the cleared edge of a firebreak. Further plants were noted further north along the firebreak in 2021 (A. Ricks pers. comm.). A survey by Rob Davis in 2023 relocated the plants at the type locality but failed to locate other plants elsewhere in the vicinity.