Orchidantha micrantha Škorničk. & A.D.Poulsen, 2017

1. Orchidantha micrantha Škorničk. & A.D.Poulsen View in CoL , sp. nov. — Fig. 1 View Fig , 2 View Fig

Similar to O. borneensis in the small habit and dark purple petals and labellum but differs in the overlapping lateral sepals supporting the labellum from below while the dorsal sepal arches above it (resulting in claw-like appearance of the flower vs sepals spreading),petals with irregularly serrate margin at apex (vs ± entire) and the curved labellum with prominently undulate margin (vs labellum more or less flat without undulate margin). — Type: A.D. Poulsen , H. B. Mathisen, Vilma B. & Jinaidi L. 2943 (holo SAR;iso E, SING), Malaysia, Sarawak, trail between Kubah National Park and Matang Wildlife Centre, N1°36ʹ46.14ʺ E110°10ʹ6.7ʺ, 50 m elevation, 19 Feb. 2014, flowering GoogleMaps .

Etymology. The epithet refers to the small flowers relative to other species of the genus.

Clump-forming herb, up to 0.8 m tall, 7–14 leaves per shoot; juvenile plants as well as adult plants with distinctly petiolate leaves; leaves to c. 1.2 m long, petiole 20–65 cm, lamina unequal, narrowly elliptic, 23–55 × 7–11 cm, base asymmetrical, obtuse to attenuate, apex attenuate. Inflorescence on a slender, branched, pale to cream-coloured, burrowing stem with prominent bracts and/or their scars; prophyll triangular, two-keeled, c. 8 mm long; second bract c. 16 mm long, shortly sharply cuspidate; third bract c. 22 mm long, shortly sharply cuspidate; floral bract appearing above the soil or with the proximal part subterranean, pale green, sometimes tinged ± purple towards apex, 35 mm long. Flowers emitting a pungent smell; pedicel c. 7 mm long; ovary extension c. 27 mm long, white to pale greenish; sepals greenish white, narrowly elliptic, shortly sharply cuspidate at apex, glabrous, entire; dorsal sepal c. 23 mm long, c. 7 mm wide; lateral sepals overlapping, often crossing and supporting the labellum, c. 25 mm long, 6–7 mm wide; lateral petals overlapping at base covering stamens and style, dark purple, elliptic, 8–8.5 mm long, c. 3 mm wide, outer margin undulate at the distal half, irregularly serrate at apex with a prominent mucro to 1 mm long; labellum ovate to elliptic with raised midrib ( 1–1.5 mm wide), c. 23 mm long (incl. the 1 mm long acuminate tip), c. 10 mm wide, dark purple throughout, with the very tip fading to a dirty orange in 2nd day flowers; sides reticulate with vertical lines much more pronounced, margin prominently undulate distally. Stamens c. 5 mm long; filaments 1.5–2 mm long; anther thecae introrse, 3–3.5 mm long, longitudinally dehiscent throughout their length. Style c. 3.5 mm long; stigma 3.5 mm long, deeply 3-lobed, conduplicate, margin irregularly denticulate, median lobe c. 2 mm long; lateral lobes c. 1.5 mm long; viscidium bluntly heart-shaped and extending from the base to about 1/3 of the lateral lobe (pronounced in side view); side of the heart-shape 1.5–2 mm long. Fruit a 3-locular, loculicidal capsule, ovoid, narrowing to a beak at apex, bluntly trigonous, c. 40 mm long (incl. the 5–8 mm long beak), c. 15 mm diam (young fruit 27 × 10 mm), dark violet to almost black externally, straw-coloured with pink-purple shades internally, dehiscing longitudinally; seeds (from not fully mature fruit) c. 6 × 4 mm, glabrous, ampulliform with a seed coat swelling at base forming a neck that bears 2–4 aril threads, aril threads up to 8–11 mm long, curled, glabrous.

Distribution — So far known only from two locations on the western side of Kubah National Park near Kuching, distanced within one kilometre from each other.

Habitat & Ecology — Kerangas forest, flat area near river ( Poulsen et al. 2029) and low dipterocarp forest, on sandy soil ( Poulsen et al. 2943). Flowering recorded in February and July.

Other specimen examined. MALAYSIA, Sarawak, Sungai Rayu , N1°37ʹ E110°10ʹ, 50 m elevation, 2 July 2003, flowering and fruiting, A. D. Poulsen, Effendy Supot, Jais & Jugah 2029 ( AAU, E, L, SAR, Sarawak Biodiversity Centre) GoogleMaps .

Conservation status — Orchidantha micrantha is reported from two populations each of several individuals a few hundred metres apart at the same general habitat within a protected area with no perceived threats. As the number of mature individuals is <1 000, it may be considered ‘Vulnerable’ (VU) D1 ( IUCN Standards and Petitions Subcommittee 2017).

Notes — 1. In Borneo, this species is most similar to O. borneensis due to its small habit, and similarity in size and colour- ing of the flower although the differences in flower structure as outlined in the diagnosis makes the two species unmistakeable. Further differences between the two species, based on examination of the type specimen of O. borneensis which has two well-preserved flowers ( Fig. 3 View Fig ) can be outlined as follows: Orchidantha micrantha has petals where the margin at apex is irregularly serrate, an ovate to elliptic labellum c. 23 × 10 mm with a prominent midrib throughout the entire length, and the margin to the stigma is irregularly denticulate whereas O. borneensis in comparison has petals with an entire margin, a linear c. 21 × 3.5 mm labellum where the midrib is only prominent in the lower half, and the stigma margin laciniate. The recently described O. ranchanensis from Sarawak also has spreading sepals and is therefore easy to distinguish from O. micrantha .

2. In continental Asia, the morphologically most similar species would be O. stercorea H.Đ.Tr ần & Škorničk. (colour figure in Trần & Leong-Škorničková 2010) and O. laotica K.Larsen (colour figure in Zou et al. 2017). Both species are small and have flowers with a dark labellum in a claw-like arrangement of pale-coloured sepals. Neither of these species has an undulate labellum margin. In addition, O. laotica has lamellate yellow stripes at the base of the labellum, while the flowers of O. stercorea are larger than those of O. micrantha .