Iguanura sarawakensis Henderson, 2025

Henderson, Andrew, 2025, A revision of Iguanura (Arecaceae, Arecoideae, Areceae), Phytotaxa 690 (2), pp. 135-188 : 176-179

27. Iguanura sarawakensis Henderson , sp. nov. Type:— MALAYSIA. Sarawak, Gunung Terpalak, Sarawak / Kalimantan border, 1 st Division, 25 September 1987, Yii Puan Ching S. 61307 (holotype SAR!, isotype NY-02326117!). Plate 10.

Stems length not recorded, 1.1(0.8–1.3) cm diameter, solitary or clustered. Leaf sheaths 11.8(8.0–14.0) cm long, tubular, mostly closed opposite the petiole, cleanly falling, covered with a thin layer of indumentum; ocreas scarcely developed; petioles 11.4(7.5–15.5) cm long; rachises 41.5(29.0–63.5) cm long; leaf blades divided, not rounded at the apex, with a deep split; leaf veins parallel; adaxial leaf veins prominent, rectangular in cross-section; pinnae 3–5 per side of rachis; middle pinna 21.9(18.0–33.0) cm long, 4.3(2.1–6.3) cm wide. Inflorescences branched to 1 or 2 orders, rarely spicate; prophylls and peduncular bracts inserted some distance apart, more or less persistent; peduncles 41.8(24.5–61.0) cm long, not wooly tomentose; rachises 3.0(0.0–9.0) cm long; rachillae 5(1–13), 15.5(8.0–25.0) cm long, 1.3(0.9–2.1) mm diameter, widely diverging from the rachis, proximal part of rachillae not with distantly spaced triads, glabrous or sparsely tomentose, not filiform with triads sunken in shallow, more or less closely spaced pits; rachilla bracts not elongate; distal triad bracteoles well-developed; distal part of flower pits glabrous; staminate flowers 2.0– 2.5 mm long with blunt apices; anther margins undulate; fruits 10.7(8.5–13.9) mm long, 6.4(5.6–7.4) mm diameter, ellipsoid, ridged, the surfaces drying smooth, white, white to red, or orange; endocarp polygonal in cross-section; endosperm homogeneous.

Distribution and habitat:— Malaysia (western Sarawak) in submontane mossy forest, montane rainforest, or forest on sandstone at 1,038(730–1,200) m elevation (Fig. 14).

FIGURE 14. Distribution of Iguanura sarawakensis , I. tenuis , I. thalangensis , and I. tomentosa .

PLATE 10. Isotype of Iguanura sarawakensis .

Taxonomic notes:— Preliminary species Iguanura myochodoides was polymorphic for four variables (stem branching, orders of inflorescence branching, rachillae diameter, pit tomentum). Three of these were treated as traits, and the fourth (rachillae diameter) was used to split preliminary species I. myochodoides into two groups. One of these was represented by a single specimen, the type of I. myochodoides . This had the same combination of characters as I. remotiflora , and is included there. The second group is recognized as a phylogenetic species, I. sarawakensis . It is characterized by its scarcely developed ocreas, non-filiform rachillae, and ellipsoid fruits.

One specimen (Jamree S.75873) has a loose packet containing staminate flowers that are 3.5 mm long. They probably do not belong to this specimen, possibly to Jamree S.75823 (here unidentified, see notes under I. magna ). Three specimens (Croat 53166, Jamree 73736, 75867) from the Serian region have spicate inflorescences and are somewhat tentatively included here.