Thismia selangorensis differs from other species of Thismia sect. Geomitra in the following combinations of characteristics: the flower is white to brownish with peach colouration; the distal part of inner tepals is arrow-like with distinct basal lobes, perfectly connate to each other when young, partly splitting on the sutures with age; mitre is wide and resembling a large umbrella, convex and trilobed when viewed from above in younger flowers, flat and irregularly hexalobed in old flowers.

Figure 2. 

Thismia selangorensis. A. Plants with flowers and roots; B. Top view of mitre (inner tepals); C. Side view of inner tepal; D. Ovary, stigma, and style; E. Floral tube with mitre removed and minute triangular outer tepal; F. Longitudinal section of floral tube with three stamens; G. Outer view of three pendulous stamens; H, I. View of inner side of floral tube, upper part (H), lower part (I); J. Bract; K. Leaf. Drawn by Mohammad Aidil Nordin from the spirit material (FRI 79179 & 79180).

Malaysia. Peninsular Malaysia: Selangor, Hulu Langat District, Taman Eko Rimba Sungai Chongkak, ca. 184 m elev., 27 November 2023, Siti-Munirah MY, Gim Siew T & Mohd Faizal MT, FRI 79179 (holotype KEP!, spirit collection, barcode no. SC13204).

Achlorophyllous ground herb, ca. 10 cm tall. Roots short, clustered, coralliform, light brown to whitish, surface covered with trichomes. Stem ca. 3 cm tall, ca. 2–3 mm in diameter, erect, unbranched, light brown, glabrous. Leaves scale-like, spirally arranged, denser at the stem tip, up to 4 mm long and 1–2 mm wide at the base, triangular-ovate to lanceolate, with pointed to acuminate tip, pale brown, glabrous. Bracts crowded, scale-like, ca. 1 cm long, 2 mm wide at the base, slightly larger than the upper leaves; triangular-ovate to lanceolate, apex acute to acuminate, brown. Pedicels ca. 2 cm long, 2–3 mm wide during the anthesis. Inflorescence near the top of stem. Flower solitary or in clusters, up to 6 cm long (including the ovary, floral tube and appendages). Perianth actinomorphic, with 6 tepals fused into a floral tube that develops into an umbrella-shaped mitre with 3 slender, claviform appendages at the tip. Floral tube narrowly urceolate, ca. 16 mm long and 4–6 mm wide, constricted above the ovary and widest in the upper part; outer surface white, peach to brownish, with 12 pale brown longitudinal stripes on the upper part, with 6 longitudinal ribs, glabrous; inner surface with 12 brown longitudinal ribs, without transverse bar but covered by a translucent white reticulation. Tepals 6; outer tepals 3, erect, minute, triangular, brownish; inner tepals 3, erect, narrowly stemmed and broadly lobed (arrow-like), apically connate and forming a mitre shape together; mitre dome to umbrella-like, convex in younger flowers and flatten as they mature (with increasing age the lobes split and change shape during anthesis), white-brownish-peach, glabrous, somewhat papery, with 3 lateral, rectangular openings, each up to ca. 10 mm tall, ca. 6 mm wide; mitre appendages 3, up to 3 cm long, 1 mm wide, broad and flattened at the base and forming a furrow in the middle of the mitre, with a club-shaped tip, brown, paler toward base and tip, glabrous. Annulus absent. Stamens 6, hanging down from the apical edge of the floral tube; filaments dark-grey-whitish to bluish coloured, bent downwards, with the bases protruding slightly beyond the apex of the floral tube, not fused, forming 6 openings visible from above. Connectives broad, bluish, fused laterally into a tube, ca. 8 mm long, each connective with conspicuous longitudinal rib extending along the entire length of the inner surface (convex on the inner surface, concave on the outer surface); supraconnective apex with a longer central lobe (an extension of the longitudinal rib) and two smaller lateral lobes with pointed tips, all glabrous; lateral appendage box-shaped, bright blue, projecting towards the floral tube without reaching the supraconnective apex, glabrous on the surface and sparsely hairy at the horn-like corners; thecae 2 on each stamen, elongated, ca. 0.8 mm long, blue-whitish; interstaminal glands elliptic-oblong, translucent, inserted at the fusion line between the connective tissues. Ovary obconical, ca. 5 mm long, 4 mm wide, dark brown, with 6 longitudinal ribs; placentae 3; style short, ca. 1 mm long, blackish; stigma 3-lobed, blackish, each lobe oblong, ca. 1 mm long and slightly bifid at the apex, the surface slightly papillose. Fruit a cup-shaped capsule.

Figure 3. 

Thismia selangorensis. A. A plant with full flower and coralliform roots; A1. Claviform tip of mitre appendage; B. Outer tepal and filaments; C. Inner tepal forming a mitre; D. Floral tube and mitre; E. Mitre viewed from above; F. Floral tube with ovary and flower bud surrounded by bracts and tepals split on apex; G. Longitudinal section of floral tube, showing inner part (H); H. Inner surface of floral tube; I. Top view of stamens; J. Inner view of a stamen; K. Outer view of a stamen; L. Six stamens viewed from below; M. Stigma. Photos by Siti-Munirah MY and Mohd Faizal; all from FRI 79179 & 79180; images not to scale (see dimensions in description and Fig. 2).

Figure 4. 

Thismia selangorensis in its natural habitat. A. Young flower that is not yet fully developed (uncollected plant); B. Mature flower living just beside the roots of a tree buttress (uncollected plant); C. A clump of T. selangorensis at different stages in its natural habitat (FRI 79182); D. A clump of flowers showing a different stage of mitre (FRI 79179 & FRI 79180). Photos by Gim Siew (A–C) and Mohd Faizal (D).

(paratypes). Peninsular Malaysia: Selangor, Hulu Langat District, TER Sungai Chongkak, ca. 184 m elev., Siti-Munirah MY, FRI 79180 (KEP, spirit collection SC13205), FRI 79182 (KEP, spirit collection SC13206).

Endemic to Peninsular Malaysia, Selangor. Currently only known from the type locality.

In lowland forests, on moist soil in the closed canopy, hidden between tree buttresses, also in tree hollows, near an open area (picnic site; Fig. 5). This species occurs in a river basin at an altitude of approximately 184 m. The site is located in a public recreational forest managed by the Selangor Tourism Authority and the Forestry Department within a watershed/riverine vegetation. The flowering season is from October to February. The forest area is a major tourist attraction for picnicking and camping. Apart from where the plant was found, part of the area looks like an intact lowland dipterocarp forest. The areas near the river are all flat and have places for a campsite. Fortunately, a few known subpopulations of T. selangorensis exist on the riverbank and near tree roots; thus, there is no known direct impact from the campground or nearby playground. However, the status of these populations may also be uncertain because activities occurring along the river could result in trampled plants.

Figure 5. 

Thismia selangorensis habitat at TER Sungai Chongkak. A. Main river of TER Sungai Chongkak and a picnic site; B. T. selangorensis type locality area; C–E. T. selangorensis living in trunk base (red arrow) beside the river; D. Plant in July 2024; E. Plant in November 2023. Photos by Siti-Munirah MY (A, C–E) and Mohd Faizal (B).

The epithet refers to the state, Selangor, where it was found.

Thismia selangorensis is a newly described species found in TER Sungai Chongkak, a recreational forest in Selangor. The species was discovered growing in moist, shaded areas near tree buttresses along the riverside. Since its initial discovery in 2023, several surveys have been conducted in the area, and fewer than 20 individual plants were recorded. All the individuals found form a single population sensu IUCN (2024). While the extent of occurrence (EOO) cannot be calculated from a single point, the area of occupancy (AOO) is formally estimated at 4 km². This species appears to be rare and only blooms at certain times of the year. It is mycoheterotrophic and typically only visible when flowering. Its flowers are often small, inconspicuous, and hidden beneath leaf litter or root buttresses. Thismia selangorensis is fragile and vulnerable to disturbances due to its small size. It is particularly threatened by trampling, especially in the main picnic area. Plants growing near the river are also at risk of being destroyed by flooding during heavy rain. Consequently, according to the IUCN (2024), this species is assessed as Critically Endangered based on B2ab(iii, v), D.

In some species of the genus Thismia, the inner tepals are fused together in the upper part and form a roof-, hat-, or umbrella-like structure known as a mitre. These species are divided into two groups: 1.) species with mitral appendages (Thismia section Geomitra and also Thismia sect. Scaphiophora); 2.) species without appendages (Thismia section Sarcosiphon). Based on the infrageneric classification of Kumar et al. (2017), Thismia selangorensis belongs to Thismia subgenus Thismia, section Geomitra (Becc.) Kumar & S.W. Gale. This classification is primarily based on the presence of inner tepals that form a mitre with three filiform appendages. According to Shepeleva et al. (2020), T. selangorensis is possibly related to the species forming Clade 3 due to its coralliform roots, fused inner tepals forming a mitre, and free mitral appendages extending from a central point. Currently, a total of seven species are assigned to section Geomitra (Table 1). In terms of species diversity within Thismia, this section represents a small group compared to other sections. To date, all known species of this section are distributed exclusively in Southeast Asia. Of the Geomitra species, only five – T. clavigera, T. clavigeroides, T. limkokthayi, T. kelantanensis and T. selangorensis – are currently found in Malaysia, with the latter three species being endemic to Peninsular Malaysia and known only from their type localities.

Morphologically, the species of section Geomitra can be easily distinguished from those of other Thismia sections by the presence of a mitre with three long appendages. In Geomitra species, the appendages are generally similar in shape and size. However, the mitre formed by the inner tepal lobes varies and produces different shapes, such as flat, concave, cap-like, umbrella-like, or bonnet-like structures. In Peninsular Malaysian species, flower colouration is also species-specific. Besides that, another important distinguishing feature of all Geomitra species compared with other Thismia species is the stamen morphology. All Geomitra species have a central rib extension in the middle of each stamen. The same stamen morphology, characterised by a central rib extension in the middle of each stamen, is also found in T. goodii, T. kelabitiana, and T. coronata (Dančák et al. 2020b). This means it is not a unique trait of species of Thismia sect. Geomitra, and the T. goodii group is probably closely related to T. sect. Geomitra species. However, the supraconnective apex of the stamens differs morphologically among T. sect. Geomitra species, being either strongly different in itself (e.g. T. limkokthayi) or only slightly different from each other (e.g. between T. clavigeroides and T. selangorensis).

In summary, it can be stated that T. selangorensis is easily recognised by a combination of the following characteristics: coral-shaped roots; mitriform inner tepals with three erect claviform appendages; absence of annulus; absence of transverse bars on the inner side of the floral tube but presence of reticulation on the inner surface; stamens with a central rib extension (convex on the inner surface, concave on the outer surface); two lateral lobes (each with pointed tips); and a blackish stigma. Thismia selangorensis shows different morphological features when compared with closely related species. A detailed comparison can be found in Table 2.