Australian Journal of
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Hibbertia elachophylla K.R.Thiele & T.Hammer, sp. nov.
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Type: Western Australia: Narkal, between Bencubbin and Koorda, c. 100 m E of the junction of Narkal North Road and Narkal Road, along the track parallel to the rail line, 19 Aug. 2021, K.R. Thiele 5697 (holo: PERTH 9428119; iso: AD, CANB, MEL).

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Figure 3. Hibbertia elachophylla, K.R. Thiele 5697.

Spreading to straggling shrubs 0.2–0.3(–0.5) m high, rather intricately but openly branched, multi-stemmed at base and probably resprouting after fire; young branchlets sparsely white-woolly at first, soon glabrous. Leaves mostly crowded at stem apices, erect at first then spreading, oblong, 2–3(–5) mm long, 0.6–1.2 mm wide, the margins revolute and meeting each other, obscuring the abaxial lamina and the rather weak, sunken midrib; petiole 0.6–1 mm long, the hypopetiole dark, ± glabrous and forming a peg on the stem when the leaves are mature, the epipetiole very short and densely white-woolly; adaxial lamina minutely muricate, glabrous except at the base where there are dense, curled-woolly, white hairs when young; abaxial surface and midrib (usually visible by dissection only) densely white-woolly; apex obtuse and pungently apiculate. Flowers sessile, terminal on short-shoots, closely subtended by crowded leaves; flower-subtending bracts 5–8, reddish brown, scarious, triangular, acute, the primary bract 2–2.5 mm long, the secondary bracts smaller. Sepals ovate, 4–5 mm long, sparsely to moderately pubescent with flexuose, sub-appressed to spreading hairs; midribs not prominent; outer sepals pungently acuminate to shortly mucronate; inner sepals similar to the outer but less acuminate and broader. Petals 5, yellow, obovate, 6–9 mm long, deeply emarginate. 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; anthers rectangular, 1.5–2 mm long, dehiscing by introrse, longitudinal slits. Staminodes absent. Carpels 2; ovaries compressed-globular, densely pubescent; styles curving excentrically from the carpel apex, 1.2–1.5 mm long. Ovules 4 per carpel. Fruiting carpels and seeds not seen.

Other specimens examined. WESTERN AUSTRALIA: (All PERTH): Between Bencubbin and Koorda (3069745, 6232957, 9428127).

For full specimen details, see the following batch search of the ALA for the above set of specimens: https://biocache.ala.org.au/occurrence/search?q=qid%3A1710635504518&qualityProfile=ALA&disableQualityFilter=scientific-name#tab_mapView

Figure 3. Hibbertia elachophylla, K.R. Thiele 5697.

Diagnostic features. May be discriminated from all other species of Hibbertia in Western Australia by the combination of very small (2–3(–5) mm long) ericoid leaves with margins that recurve to each other, hiding the midrib, 10 stamens, and 4-ovulate carpels.

Phenology. Flowering specimens have been collected from mid-August to early October.

Distribution and habitat. Occurs in south-western Western Australia, where known only from the area around Narkal, between Bencubbin and Koorda. Occurs in low, open mallee-heath on a yellow sandplain.

Conservation status. Hibbertia elachophylla is known from only two localities, one of which is in a conservation reserve. Its conservation status should be assessed.

Etymology. From the Greek elachys (small, short) and phyllon (a leaf), in reference to the notably small leaves of the species.

Notes. Hibbertia elachophylla has unusually small leaves, but in other respects is morphologically fairly similar to H. arenicola and H. erioclada. Those species differ in having leaves with a robust midrib that the recurved margins tightly abut, rather than a weak, sunken midrib. Hibbertia axillibarba differs in having longer leaves and larger flowers with 2-ovulate carpels.{p}