Mezoneuron hildebrandtii Vatke, 1882

Clark, Ruth P., 2016, A Taxonomic Revision of Mezoneuron (Leguminosae: Caesalpinioideae: Caesalpinieae), Phytotaxa 274 (1), pp. 448-450 : 448-450

3. Mezoneuron hildebrandtii Vatke

Linnaea 43: 338-340. 1882. (as Mezoneurum )

Type:— MADAGASCAR: NW Madagascar, Nosi-Be, Hildebrandt 3399.

Lectotype (here designated):—JE (JE00000390, image!); isolectotypes JE (JE00000391, image!, JE00000392, image!), (K000232354!), L (L0651495!), M (M0108401, image!), P (P00131733!).

Synonym. Caesalpinia hildebrandtii (Vatke) Baillon Bull. Mens. Soc. Linn. Paris i: 371. 1883.

Synonym. Caesalpinia grevei Baillon. In Grandidier, Hist. Phys. Madagascar, Plantes, Atlas 1: plate 24B & 24CA. 1887.

Type:—Illustration in loc. cit., Atlas 1: plate 24B & 24C

K

Scrambling or thicket forming shrub, or liana, to 10 m in length. Stems with recurved prickles, older stems with robust, woody, spine-tipped tubercles; glabrous. Stipules caducous, triangular, 1–2 × 1–2 mm, glabrous. Leaves with (2–) 3–8 (–9) pairs pinnae; 4–7 (–8) pairs leaflets per pinna; petiole 3–6.5 cm; rhachis 8–25 (–30) cm, with recurved prickles paired at the pinna insertion points, and scattered on the internodes; pinnae 6–10 cm; leaf rhachis,

10 • Phytotaxa 274 (1) © 2016 Magnolia Press

CLARK petiole, and pinna rhachis sparsely to moderately tomentose. Leaflets opposite to alternate; the terminal leaflets slightly obovate, base oblique, apex rounded to retuse, 1.4–3 × 0.8–2 cm; lateral leaflets elliptic to oblong, suborbicular, or slightly obovate, base oblique, apex rounded to retuse, 1.3–2.6 × 0.7–2 cm; all leaflets with upper surface glabrous, lower surface glabrous, or with few hairs on lower midvein; 2˚ venation anastomosing, 3˚ venation reticulate, not or scarcely visible above, slightly visible below. Inflorescence a panicle, terminal and in the upper leaf axils, to 30 cm; sometimes with scattered recurved prickles on the lower axes; the axes glabrous; pedicels 3–7 mm, not articulated, glabrous. Bracts persistent, semicircular to triangular, ca. 1 × 1 mm, glabrous; bracteoles caducous, lanceolate, long-acuminate, 2–3 × 0.5–1 mm, glabrous. Flowers with a hypanthium ca. 1 × 3–4 mm; lower calyx lobe 5–6 × 2–3 mm, the margin usually with small, irregular teeth; other lobes 3–5 × 2–3 mm; hypanthium and calyx lobes glabrous. Median petal obovate, with pronounced transverse flap of tissue on inner surface between claw and blade; 3–5 × 2–3 mm, the flap of tissue and margins of the claw tomentose. Upper lateral petals obovate to suborbicular, ca. 3–6 × 2–3 mm including claw ca. 1 mm; outer surface glabrous, inner with few hairs on claw and lower blade. Lower lateral petals obovate, ca. 6 × 2.5 mm, including claw ca. 1 mm long; outer surface glabrous, inner with few hairs on claw and lower blade. Stamen filaments flattened, 7–10 × 0.5 mm long; densely villous on the basal half on inner surface; anther 1–1.5 mm. Ovary 5–10 mm long, style ca. 5–8 mm long; both glabrous; stigma funnel-shaped, ca. 1 mm wide, the rim papillate. Fruit chartaceous, elliptic, base attenuate, with stipe 2–5 mm, apex acute to acuminate, or retuse; 6.5–14 × 2–4 cm; wing arising basally ca. 6–10 mm along the central vein, 5–12 mm wide, fruit surface glabrous, glossy; venation reticulate, raised and clearly visible on fruit body, not visible on the wing; hypanthium persistent. Seeds 1–2 (–3) per fruit; discoid to ovatediscoid, visible in outline on fruit exterior when mature, 7–9 × 6.5–8 × 2.5–3 mm, smooth, matte, olive green or tinged brown.

Distribution:—Endemic to Madagascar: W & N Madagascar, from Antsiranana south to Morondava, including the Sambirano (but absent from south-west Madagascar) ( Du Puy et al. 2002). ( Fig. 4).

Habitat and ecology:— Deciduous woodland and scrubland, often in exposed situations including bare limestone ‘tsingy’ and along river margins, on limestone or sandy soils. Deciduous forest, scrub, red laterite soil. Elevation sea level to 600m.

Phenology:—Flowering April–June, fruiting May–June.

Conservation assessment:—The species has a wide distribution range across Madagascar, where it appears to

A TAXONOMIC REVISION OF MEZONEURON

Phytotaxa 274 (1) © 2016 Magnolia Press • 11 be generally common and no major threats are known to affect the species at present, therefore Mezoneuron hildebrandtii is rated as Least Concern ( IUCN 2015).

Field notes:—Flowers white.

Taxonomic notes:—The lectotype was selected on the basis of being housed at JE, the institution at which the specimens of author of the species name, Vatke, are primarily stored, and on being representative of the species.