Hibbertia coracula K.R.Thiele, sp. nov.

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Wongonderrah Rd 0.5 km W of the Brand Hwy, on firebreak, S side of road, 25 Aug. 2018, K.R. Thiele 5525 (holo: PERTH 9247211; iso: AD, CANB)

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Erect, usually openly-branched shrubs 0.3–0.4(–0.6) m high, with several to many stems at base and resprouting after fire; young branchlets glabrous or sometimes with scattered, minute, simple to sub-stellate hairs below the leaf insertions, with tufts of short hairs in the leaf axils. Leaves spreading, scattered, narrowly oblong, ovate, elliptic or obovate, (3–)4–6(–25) mm long, 1–3(–5) mm wide, thick-textured, usually distinctly but shallowly incurved, the margins usually rather loosely recurved and the abaxial surface visible (rarely tightly recurved to the midrib); adaxial surface smooth (rarely obscurely tuberculate), glabrous except for some minute hairs at the base and on the margins of the petiole; abaxial surface glabrous; apex obtuse but the midrib shortly excurrent and ± pointed, straight to incurved. Flowers sessile, terminating short-shoots or main stems; flower-subtending bracts 3–6, ovate, chartaceous, 2.2–5 mm long, acute, glabrous except for the minutely ciliolate margins, the lowermost sometimes with reduced leaf blades. Sepals ovate, 4.5–8 mm long, glabrous except for the minutely ciliolate margins; midribs not prominent; outer sepals acute; inner sepals similar in size and apex shape to the outer but broader, slightly thinner and with scattered, minute, sub-stellate hairs. Petals 5, yellow, broadly obovate, 8–12 mm long, emarginate or entire. Stamens 10(11), all on one side of the gynoecium and curving over it like a hand of bananas; filaments 0.5–1 mm long, fused at the base into a robust claw; anthers rectangular, 2–2.5 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, 1.2–2.2 mm long. Ovules 2 per carpel. Fruiting carpels and seeds not seen.

Selected specimens examined (all PERTH): Badgingarra (6934242, 6313035, 3069478, 9330348), Beckenham (3043789), Cannington (3043851, 3043843), Cataby (9394087), Cockleshell Gully (3043134, 3070034, 3043711, 3021424), Coorow (3069354, Eneabba (3070018, 3021408, 8828210, 8035377, 5685915), Gingin (3044084, 3043398, 3043797), Gnangara (3043800), Green Head (9330291, Kenwick (9128018), 9247173), Kulin (5802199), Lake Indoon (3069672), Lake Logue (3069583), Muchea (5379377), Mullering Brook (3044076, 3044068), Regan's Ford (3069443), Wanneroo (9259201). 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:1665049023584#tab_mapView

Diagnostic features. Distinctive within the Hibbertia crassifolia-H. aurea species group in having leaves that are smooth and glabrous both adaxially (except for some minute hairs at the base and on the margins of the petiole) and abaxially, with margins that are usually rather loosely recurved so that the glabrous abaxial surface is visible, and with the lamina usually slightly incurved.

Phenology. Flowers from late June to early October, with a peak in September.

Distribution & habitat. Occurs in south-western Western Australia, from Eneabba south to Perth, mostly in a narrow strip immediately east of the eastern boundary of the Swan Coastal Plain IBRA Region (Fig. 6). Two disjunct collections are from Coorow (c. 60 km east of the main range), and near Kulin (c. 230 km ESE of the main range); both specimens appear typical for the species. Occurs in open woodlands with heathy understories, on sand.

The disjunct specimen from Kulin is surprising given the overall distribution of the species. More collections from that area would be welcome.

Conservation status. Hibbertia coracula is widely distributed, including in a number of national parks and nature reserves, and is not considered to be under threat.

Etymology. From the Gaelic curachan, anglicised as 'coracle', a small, rounded, woven boat, in reference to the unusual, often somewhat boat-shaped leaves.

Notes. Hibbertia coracula is a distinctive member of the H. aurea-H. crassifolia species group. The (usually exposed) glabrous abaxial lamina and rather incurved, boat-shaped leaves are distinctive. Some specimens from the vicinity of Badgingarra (e.g. Thiele 5639, Hayes BRTA 152) have broadly elliptic leaves with the margins scarcely recurved and the abaxial lamina fully visible, while in others (e.g. Cranfield 1474) the margins are strongly recurved to the midrib and the abaxial lamina is almost entirely hidden. There are clear intermediates between these extremes and more average specimens, where the leaves are somewhat but not strongly recurved.