Costus acutissimus Maas &amp; H. Maas 2016, sp. nov.
Creators: name: Kamer 1, H. Maas-van de
name: Maas 1, P. J. M.
name: Wieringa 1, J. J.
name: Specht, C. D.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Zingiberales
Costaceae
Costus
Costus acutissimus

description: <b> 1. <i>Costus acutissimus</i> Maas &amp; H.Maas</b> , <i>sp. nov. —</i> Fig. 3; Map 2 <i>Costus acutissimus</i> is characterized by narrow leaves with a long-acute apex (hence the specific name),a very short ligule (1–2 mm long), a globose inflorescence (6–8 cm diam) terminating a separate flowering shoot, green appendaged bracts and white flowers with yellow nectar guide. — Type: <i>Van Valkenburg et al. 2768</i> (holo WAG 3 sheets [WAG0120332, WAG0120333, WAG0120334]; iso BR, LBV [LBV0003152, LBV0003153], MO, P), Gabon, Nyanga, Moukalaba, Doudou National Park, Chantier SFN-Bakker, 250 m, 16 Feb. 2004. Terrestrial herb to c. 3 m tall. <i>Leaves</i> many; sheaths 0.5–2 cm diam, falling apart into separate fibers with age and leaving a distinct horizontal rim at the nodes near the base of the shoot; ligule chartaceous, 2-lobed, 1–2 mm long; petiole 1–3 mm long; sheaths, ligule and petiole glabrous to sparsely covered with minute appressed hairs &lt;1 mm long and upper margin of ligule and sheaths with irregular curly fibers to c. 10 mm long; lamina narrowly elliptic, 17–30 by 3.5–7 cm, glabrous on both sides, base obtuse to cordate, apex long-acute to sometimes acuminate (acumen to c. 20 mm long). <i>Inflorescence</i> manyflowered, globose, 6 – 8 by 6 –8 cm, terminating a separate leafless shoot 10–30 cm long; bracts, appendages of bracts, bracteoles, calyx, ovary and capsule sparsely covered with appressed hairs &lt;1 mm long to glabrous; margin of bracts and calyx lobes densely covered with irregular curly fibers c. 1 mm long. <i>Flowers</i> 2 per bract; bracts pale green, chartaceous, broadly ovate-triangular, 2–4 by 2–3 cm, callus absent; ap-pendages green, ascending, broadly ovate-triangular, 1– 2 by 1–2 cm; bracteole boat-shaped, 20–25 mm long, callus absent; calyx 25–28 mm long, sometimes split to the base on one side, lobes narrowly triangular, 5–7 mm long, callus absent; corolla white (not seen); labellum white, inner side with yellow nectar guide (not seen); stamen yellow (not seen). <i>Capsule</i> ellipsoid to obovoid, 10–17 by 7–10 mm. <i>Seeds</i> c. 1.5 by 1–1.5 mm. Distribution — Central Africa (Cameroon, Gabon). Habitat &amp; Ecology — In moist valley bottom and on steep hill side. At elevations of 250– 500 m. Flowering and fruiting: February, May. IUCN Conservation Status — Based on an AOO of only 8 km 2 in two quite disjunct locations that both are part of National Parks, we assess this species as Vulnerable (VU): D2. <i>Other specimen examined.</i> CAMEROON, <b>South-West Province</b>, S of Esukutang, 300–500 m, 25 May 1988, <i>Thomas et al. 7938</i> (MO). Note — Young shoots of <i>C. acutissimus</i> often show swollen nodes and small bulbils in the upper part of the shoot (Fig. 3b). Old shoots have distinct horizontal rims of c. 1 mm high, presumably remnants of withered sheaths (Fig. 3a).
description: Published as part of <i>Kamer 1, H. Maas-van de, Maas 1, P. J. M., Wieringa 1, J. J. &amp; Specht, C. D., 2016, Monograph of African Costaceae, pp. 280-318 in Blumea 61 (3)</i> on page 290, DOI: 10.3767/000651916X694445, http://zenodo.org/record/7570023