Iguanura bicornis Beccari (1889: 188)

Henderson, Andrew, 2025, A revision of Iguanura (Arecaceae, Arecoideae, Areceae), Phytotaxa 690 (2), pp. 135-188 : 148

3. Iguanura bicornis Beccari (1889: 188) . Lectotype (designated by Lim 1998 a):— MALAYSIA. District of Perak in the Malay Peninsula, G. Ijuk , August 1884, B. Scortechini 1186 (lectotype FI-014158!). Plate 2.

Stems 1.5 m long, 0.7(0.5–1.0) cm diameter, solitary or clustered. Leaf sheaths 11.0(8.0–15.5) cm long, tubular, mostly closed opposite the petiole, cleanly falling, covered with a thin layer of indumentum; ocreas scarcely developed; petioles 13.9(5.8–21.5) cm long; rachises 38.1(24.0–53.0) cm long; leaf blades divided, not rounded at the apex, with a deep split; leaf veins diverging; adaxial leaf veins not prominent, triangular in cross-section; pinnae 5(2–8) per side of rachis; middle pinna 15.1(12.8–19.7) cm long, 5.9(3.5–9.5) cm wide. Inflorescences branched to 1 order; prophylls and peduncular bracts inserted close together at base of peduncle and both early deciduous before anthesis; peduncles 2.5(1.0–4.7) cm long, not wooly tomentose; rachises 2.5(0.5–6.0) cm long; rachillae 6(3–12), 9.8(5.5–17.0) cm long, 1.4(0.9–2.2) 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 scarcely developed or absent; distal part of flower pits glabrous; staminate flowers 2.0– 2.5 mm long with blunt apices; anther margins not undulate; fruits 12.1(9.9–14.0) mm long, 5.7(4.8–6.8) mm diameter, obovoid, bilobed at apex, not ridged, the surfaces drying pebbled, red or white; endocarp circular in cross-section; endosperm homogeneous.

Distribution and habitat:—Southern Peninsular Thailand and northwestern Peninsular Malaysia in evergreen forest or hill Dipterocarp forest at 809(210–1,300) m elevation ( Fig. 7 ).

Taxonomic notes:— Preliminary species Iguanura bicornis was polymorphic for one variable (stem branching). This was treated as a trait. It then had a unique combination of qualitative character states and is recognized as a phylogenetic species. It is characterized by its fruits that are bilobed at the apices ( Plate 2). It has densely reddish-brown tomentose stems, at least when first exposed from the leaf sheath, and this distinguishes sterile specimens from the sympatric I. polymorpha . Saw (2023) included Burkill 6299 in I. bicornis , but the immature fruits do not appear lobed, and the inflorescence appears more like those of I. polymorpha , where it is here placed.

Subspecific variation:—Specimens of I. bicornis are from three, separate areas ( Fig. 7 ). There are two specimens from Peninsular Thailand, near the northwestern Thailand-Malaysia border. These do not appear to differ from the second group of specimens, from the central region of the Thailand-Malaysia border. The third group is from Bukit Larut in Perak, Peninsular Malaysia. These specimens are from higher elevations and are noticeably smaller than the others. They have narrower leaf blades with fewer pinnae and less diverging veins, with the distalmost pair of pinnae wider than the others. One specimen (Mhd. Haniff SFN 9090) at SING has two leaves, one undivided and the other with three pinnae per side of the rachis. This third group of specimens is from the same locality as I. brevipes .

Figures

FIGURE 7. Distribution of Iguanura australis, I. beccarii, I. bicornis, and I. borneensis.