Aerangis bovicornu Hermans, Kew Bull. 76: 40 (2021).
Description:
Short monopodial epiphytic herb up to 5 x 6.5 cm, with a short woody stem c. 8 mm in diam., covered in brown corrugate sheaths, bearing numerous somewhat hirsute orange-brown roots becoming grey with age, c. 1.5 mm in diam. Leaves 3 - 5, leathery, on a short 3 - 5 mm conduplicate petiole, ovate to elliptic, 20 - 33 x 16 - 22 mm, somewhat convex, emarginate at the tip, laevigate, more or less brownish-orange on the upper surface, greyish-green, punctate underneath with the central vein darker. Inflorescence very short, up to 2.5 cm long, bearing 2 - 3 flowers and an aborted bud. Rachis 3 -5 mm in diam., orange-brown, almost entirely covered with 2 - 3 conduplicate to almost tubular bracts, 3.4 - 4.8 x 1.8 - 2.1 mm. Floralbracts thin, amplexicaul, 1.8 - 2.3 x 1.8x2 mm. Flowers c. 10 x 10 mm without the spur, about 10 mm apart, stellate, not opening fully; petals, sepals and lip white with the tips sometimes tinged with orange, the ovary and spur orange-brown, the buds green. Pedicel and ovary straight, rounded, slightly ridged, 8 - 12x 1.9 -2.3 mm. Dorsal sepal ovate-elliptic, acuminate, 7.8 - 8.6 x 3.6 - 3.9 mm, narrowed, reflexed towards the base. Lateral sepals obliquely lanceolate, acuminate, 8.7 - 8.9 x 3.5 - 3.7 mm. Petals ovate elliptic, obtuse, 8.3 - 8.6 x 3.8 - 4.1 mm. Lip ovate-lanceolate, attenuate, 7.6 - 8.2 x 3.9 - 4.1 mm; spur slender, horn-shaped, terete at the tip, a little broadened towards the base, 20 - 23 x 0.9 - 1.3 mm. Column short, stout, slightly winged, broadly mucronate at the apex, rostellum ligulate-ensiform, up to 5 mm long; anther broadly obovoid with a small rounded swelling at the apex, up to 1.4 x 1.6 mm; pollinia globose c. 0.8 x 0.6 mm, stipes short and slender, viscidium elongate, narrow. Seed capsule fusiform, glabrous, brown, 16 x 5 mm.
Etymology:
The epithet refers to the typical shape of the spur, resembling a bull’s horn, especially that of the local Madagascan zebu cattle.
Recognition:
Aerangis bovicornu is a few-flowered compact plant with small flowers that do not open fully, ovate to elliptic leaves which are brownish-orange on top and greyish-green underneath; the stellate flowers have a short horn-shaped spur and white perianth with an orange-brown ovary and spur and long rostellum and anther with a small rounded swelling at the apex. It is undoubtedly most closely related to Aerangis fastuosa (Rchb.f.) Schltr. (Schlechter 1914: 598) but differs substantially in its flowers which are consistently a third of the size, the straight slender, up to 23 mm long, spur which is consistently much shorter (vs a minimum of 76 mm in A. fastuosa), the perianth tips and spur coloured brownish-orange (vs generally white), the narrower column apex and the obovoid anther with a small rounded swelling at the apex (vs conical with a long beak).
Habitat:
Epiphyte on small moss- and lichen-covered trees in remnants of forest on granite inselberg. Elevation c. 1800 m.
Phenology:
Flowering in December to January.
Notes:
At first sight Aerangis bovicornu could be considered another local variant of Aerangis fastuosa, especially as it comes from a relatively accessible region but closer examination proves otherwise. They share the leaf shape, short rachis, shape of the perianth and the long rostellum but size of all the floral parts, spur length, column and anther shape and colour are all very different. The characteristics of the new species were found to be consistent within the local colony of about 20 plants which consisted of plants with flowers that were just opening and others that had almost wilted.
Distribution:
Endemic to south-central Madagascar, Fianarantsoa province, only known from the type collection.
References:
New species in Orchidaceae from Madagascar by Johan Hermans, Landy Rajaovelona & Phillip Cribb. KEW BULLETIN Published online: 15 March 2021; POWO (2022). "Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/ Retrieved 18 November 2022."
Images:
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