Iguanura chaiana Kiew (1979: 144)

Henderson, Andrew, 2025, A revision of Iguanura (Arecaceae, Arecoideae, Areceae), Phytotaxa 690 (2), pp. 135-188 : 154

7. Iguanura chaiana Kiew (1979: 144) . Type:— MALAYSIA. Sarawak, 2 nd Division, Bukit Ubah-Ribu, Ulu Sg. Kaup, Lubok Antu, 12 March 1974, P. Chai S.33784 (holotype SAR!, isotype BH!).

Stems length not recorded, 1.9 cm diameter, solitary. Leaf sheaths 16.6(15.5–18.0) cm long, open and more or less persistent, not cleanly falling, initially covered with dense, woolly indumentum; ocreas scarcely developed; petioles 4.9(1.0–9.5) cm long; rachises 91.7(80.0–114.0) 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 18(14–27) per side of rachis; middle pinna 33.0(24.0–41.5) cm long, 2.5(2.1–2.8) cm wide. Inflorescences branched to 2 orders; prophylls and peduncular bracts inserted some distance apart, more or less persistent; peduncles 80.3(66.0–104.0) cm long, not wooly tomentose; rachises 18.3(12.0–25.0) cm long; rachillae 26(18–35), 18.3(12.0–23.0) cm long, 0.6(0.5–0.7) mm diameter, not diverging from rachis, the proximal, adaxial rachilla surfaces flat, lying close to the flat rachis surface, proximal part of rachillae with markedly distantly spaced triads, glabrous or sparsely tomentose, filiform with superficial, distantly spaced triads; rachilla bracts not elongate; distal triad bracteoles well-developed; distal part of flower pits densely tomentose; staminate flowers 2.0– 2.5 mm long with blunt apices; anther margins undulate; fruits 8.7 mm long, 5.7 mm diameter, ellipsoid, ridged, the surfaces drying pebbled, white or whitish-yellow; endocarp polygonal in cross-section; endosperm homogeneous.

Distribution and habitat:— Malaysia ( Sarawak) in hill Dipterocarp forest, riparian forest, or sub-montane forest at 748(500–1,120) m elevation ( Fig. 8 ).

Taxonomic notes:— Preliminary species Iguanura chaiana had a unique combination of character states and is recognized as a phylogenetic species. It is characterized by its rachillae that do not diverge from the rachis, the proximal, adaxial rachilla surfaces flat, lying close to the flat rachis surface, and filiform rachillae with superficial, distantly spaced triads. It is notable for its short petiole, long rachis with 14–27 pinnae per side (more than any other species), inflorescence with numerous rachillae, and flower pits with a dense tuft of hairs distally.

The staminate flowers are so small it is difficult to see whether the anthers are undulate or not. They were reported by Kiew (1979) to be non-undulate. On the specimen (Julaihi S.77542) with the most mature staminate flowers they appear to be slightly undulate, and are so scored. Kiew (1979) described the fruits as not ridged, but the fruits of the isotype, possibly not seen by Kiew, and of other specimens, are clearly ridged.

Figures

FIGURE 8. Distribution of Iguanura brevipes, I. bruneiensis, I. chaiana, and I. curvata.