Bulbophyllum sungaiutikense F.H.Kurniawan, Yudistira & Mustaqim, sp. nov. (Figs 1, 2)

Type:— INDONESIA. Kalimantan Barat Province: Kapuas Hulu Regency, Embaloh Hulu District, Batu Lintang Village, Sungai Utik Hamlet, 19 Jan 2022, fl., Kurniawan 01 (holotype: FIPIA).

Bulbophyllum sungaiutikense is similar to B. nabawanense Wood & Lamb in Chan et al. (1994: 73), but differs in having tetragonal lateral sepals with more elongate triangular apical part and length per width ratio of 2.4−2.6 (vs. triangular, apex acute, length per width ratio 1.3−1.4), petal with an elongate acuminate apex (vs. acute), labellum longer (length per width ratio 2.7−3.2 vs 1.0−1.3), caudate (vs. acute to obtuse) and verrucose surface (vs. somewhat wrinkled).

Epiphytic or creeping terrestrial herbs. Rhizome 1.0− 1.5 mm in diameter, distance between pseudobulbs 2.0− 3.7 cm. Pseudobulbs subconical cylindric, slightly flattened, 3.0−3.4 × 0.6−0.7 cm. Leaf petiole 0.5−1.0 cm long, blade elliptic to ovate, 8.8−9.8 × 2.5−3.7 cm, length per width ratio 2.6−3.5, acuminate, margin entire. Inflorescence from the base of pseudobulb, more or less patent, 6.6−9.5 cm long, 1-flowered, peduncle 5.5−9.4 cm, with 4 flowerless bracts, uppermost bract ovate, 9.2−9.5 × 4.5−4.9 mm, apex acute, basal node of pedicel approximately level with the floral bract attachment. Flowers opening widely, fragrance of rotten fish at anthesis, pedicellate ovary 12−15 mm long, straight, ribs rounded, glabrous. Sepals and petals yellow to cream with purple veins and margins, labellum purple at margins, paler towards the middle, dorsal sepal free, somewhat incurved, narrowly triangular-ovate, 27.2−34.1 × 6.8−8.4 mm, length per width ratio 3.9−4.1, acute, margins entire, glabrous, 5-veined, lateral sepals oblique, the lower 4/5 tetragonal, upward narrowly triangular, 31.7−34.6 × 12.4−14.7 mm, length per width ratio 2.4−2.6, petals triangular, slightly falcate, 22.2−24.8 × 6.5−6.7 mm, length per width ratio 3.4−3.7, acute, margins entire, recurved at the base, glabrous, 5-veined, labellum slightly recurved in lowest third, dorsoventrally flattened near the base, subsagittate, 22.7−24.0 × 7.2−9.0 mm (not flattened), length per width ratio 2.7−3.2, apex long caudate, margin curved upward, entire, adaxially concave from the basal towards apical part due to upturned margins, more slightly so towards the apex, with shallow, longitudinal median furrow from the base to near the apex, gradually verrucose toward the margin, verrucae conical, abaxially with distinctly grooved on the base, upward with two thin ridges towards the apex, glabrous; column including stelidia 2.9−3.2 mm long, glabrous, stelidia deltoid, obtuse to rounded, with additional short antrorse subcuspidate part, c. 1.0 mm long, tooth present, patent to horizontal, distinct in half of the lower margins, narrowly triangular, 2.38−2.40 mm long, tapering toward the blunt tip, anther cap obdeltoid, the anterior part of connective drawn out, slightly erose, ridge distinct abaxially, glabrous. Pollinia 4, in two pairs.

Distribution:— Endemic to Indonesian Borneo, Kalimantan Barat Province, known only from the type locality (Fig. 3).

Etymology:— Named for Sungai Utik, the hamlet where the type specimen was collected.

Habitat and ecology:— Growing terrestrially in peat swamp hummus or epiphytically in shrubs or treelets, no more than 1 m above the ground, in warm (23–33°C) conditions with high humidity (80–90%) and canopy cover between 75–85%, in podzolic soil at 70–100 m.

Phenology:— Flowering January–March.

Conservation status: —Known from the type locality with the surrounding forests poorly explored. At present, the forest is sacred and protected by the local people from conversion (e.g. to palm oil production), and therefore disturbance is unlikely in the foreseeable future. Using guidelines of IUCN (2012) and IUCN Standard Petition and Committee (2022), we propose this species as data deficient (DD) until further study/exploration.

Notes:— Bulbophyllum sungaiutikense belongs to the B. sect. Beccariana Pfitzer (1889: 179) due to its singleflowered inflorescence, flat bracts, 5-veined sepals with the dorsal sepals free with an entire margin, either glabrous or papillose (Vermeulen et al. 2015). The most similar species is B. nabawanense, an endemic of Nabawan, Sabah, which also known from a single locality at a higher elevation (400–500 m; Vermeulen et al. 2015).

Following the key to B. sect. Beccariana in Borneo by Vermeulen et al. (2015), this species appears to be morphologically allied to B. aeolium Ames (1914: 429), from which B. sungaiutikense differs in its single-flowered inflorescence (vs. multiple flowered), labellum with the lateral profile highest near the base (vs halfway of its length) and longer length per width ratio (2.7−3.2 vs 1.0−1.4) and the drawn-out connective (vs short).

Due to its single-flowered inflorescence and ovate to triangular petals, winged stelidia and glabrous labellum, this species could be considered a member of the B. uniflorum- group with four other Bornean species (Vermeulen et al. 2015): B. artvogelii Vermeulen, O’Byrne & Lamb in Vermeulen et al. (2015: 208), B. aeolium, B. uniflorum (Blume 1825: 309) Hasskarl (1844: 39) and B. ericssonii Kraenzlin (1893: 522). From all these species, B. sungaiutikense is distinguished by its subsagittate long labellum (> 20 mm long) with adaxial verrucose surface and central groove, the anterior portion of which is connective drawn out and slightly erose.

Additional specimen examined:— INDONESIA. Kalimantan Barat Province: Kapuas Hulu Regency. Embaloh Hulu District, Batu Lintang Village, Sungai Utik Hamlet, 13 Mar 2022, fl., Kurniawan 02 (BO).