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Pleurandra crassifolia Turcz., Decas sexta generum plantarum hucusque non descriptorum adjectis descriptionibus specierum nonnullarum. Bulletin de la Societe Imperiale des Naturalistes de Moscou 22(3): 5, (1849). Type statement: "Nova Hollandia, Drum. IV. n, 120.". Type: Drummond 120 (syn: KW 1000423 image!, M 212923 image!, MEL 666826!, TCD 9679 image!, K 687501 image!, K 687502 image!).
Figure 2. Distributions of Hibbertia crassifolia (A), H. consuta (B), H. coracula (C) and H. jayhornii (D) in southwestern Western Australia.
Erect to spreading shrubs (0.15–)0.3–0.6 m high, with several to many stems at base and resprouting after fire; young branchlets moderately to densely pubescent to pilose with whitish, spreading, simple hairs. Leaves spreading, scattered, narrowly oblong, ovate or obovate, (4–)6–8(–10) mm long, 1–2 mm wide, thick-textured, the margins strongly recurved (usually to each other) and obscuring the abaxial surface, the midrib not prominent; adaxial surface densely tuberculate, pilose with long, spreading simple hairs from the tubercles (rarely with some of the shorter hairs hooked), the indumentum wearing off with age; abaxial surface (mostly obscured by the margins) pilose on the lamina and midrib; apex obtuse or with a short, thickened point, straight. Flowers sessile, terminating short-shoots or main stems; flower-subtending bracts 9–14, 6–8 mm long, narrowly ovate to narrowly triangular, acute, chartaceous, usually abundantly pilose especially along the midrib, at the apex and on the margins, the lowermost sometimes with reduced leaf blades. Sepals ovate, 6–8 mm long; midribs not prominent; outer sepals acute to acuminate, usually glabrous except for some fine, pilose hairs towards the apex and on the margins; inner sepals similar in size and apex shape to the outer but broader, slightly thinner, and with an indumentum of short, sub-stellate hairs. Petals 5, yellow, broadly obovate, 8–12 mm long, emarginate or entire. Stamens 10, all on one side of the gynoecium and curving over it like a hand of bananas; filaments 0.5–0.8 mm long, fused at the base into a robust claw; anthers rectangular, 1.8–2.5 mm long, dehiscing by introrse, longitudinal slits. Staminodes 2(3) either side of the stamens. Carpels 2; ovaries compressed-globular, densely pubescent; styles inserted excentrically on the carpel apex, parallel and curved beneath the stamens, 1.2–1.8 mm long. Ovules 2 per carpel. Fruiting carpels and seeds not seen.
Other specimens examined (all PERTH): Alexander Morrison National Park (3069311, 3069338, 3069508, 6694780, 9247181), Watheroo National Park (3069737, 7233779), Big Soak Plains (7257449), W of Coorow (3069540, 3069559). For full specimen details, see the following batch search of the ALA for this set of specimens: https://biocache.ala.org.au/occurrences/search?q=qid:1664578467361#tab_mapView
Figure 2. Distributions of Hibbertia crassifolia (A), H. consuta (B), H. coracula (C) and H. jayhornii (D) in southwestern Western Australia.
Diagnostic features. Hibbertia crassifolia can be distinguished from all other species in the H. aurea-H. crassifolia species group by the combination of short, thick, obtuse, usually sparsely pilose leaves with a weak midrib, the margins recurved to each other so that the midrib is obscured at least in dried leaves, and in having 9–14 narrowly ovate to narrowly triangular, usually pilose bracts subtending the calyx.
Phenology. Flowers in July to October with a peak in September.
Distribution & habitat. Occurs in south-western Western Australia, in the southern Geraldton Sandplains IBRA bioregions, in and around Alexander Morrison National Park (Fig. 4), in kwongan shrublands and mallee on pale grey to white sandplains.
Conservation status. Although restricted to a relatively small area the species is common including in a number of national parks and nature reserves.
Notes. Hibbertia crassifolia, as circumscribed prior to this paper, was regarded as widespread, occurring from Three Springs south to near Perth and inland to Calingiri and Tarin Rock. However, its circumscription and geographic range are greatly reduced here, through the segregation of H. consuta, H. coracula, H. ericoides, H. jayhornii and H. williamsiorum. Amongst these species, H. crassifolia is distinctive in having very short, thick-textured leaves (4–)6–8(–10) mm long that are usually densely tuberculate and very obtuse, with usually spreading simple hairs from the tubercles adaxially and pilose hairs abaxially, with the leaf margins recurved to each other at least when dried and obscuring the pilose midrib (which is thus not prominent).
Amongst the segregates of H. crassifolia sens. lat., H. consuta is superficially most similar to H. crassifolia sens. str. and is narrowly allopatric with it (occurring to the north of the range of H. crassifolia). It differs in having leaves that are not strongly tuberculate, are glabrous or shortly pubescent, and have a strong abaxial midrib with the margins recurved to the midrib rather than to each other, and with a dense, cottony pubescence on the abaxial lamina visible as two strips of dense indumentum either side of the midrib.
Hibbertia jayhornii is also superficially similar, but the midrib in that species is almost always exposed and glabrous (or at most has very sparse, tubercle-based hairs) and the leaf abaxial surface is densely papillate rather than pilose. Leaves in H. jayhornii are usually longer and narrower (5–15 mm long × 0.7–1.3 mm wide in H. jayhornii, 4–10 mm long × 1–2 mm wide in H. crassifolia) and have sparser, coarser tubercles with longer, sparser, more prominently tubercle-based pilose hairs.
Two specimens, Blackall 3957 and 3970, labeled 'W of Coorow' are imprecisely georeferenced; at PERTH, these specimens are georeferenced as at Coorow, but the species probably does not occur that far east.
Typification. Amongst the syntypes, K 687502 and M 212923 do not have a Drummond collecting number; however, all the cited type specimens are very similar and there is no reason to doubt that these un-numbered specimens comprise parts of the same gathering as the rest of the series.