Mezoneuron nhatrangense Gagnep.

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

6. Mezoneuron nhatrangense Gagnep.

Bull. Mus. Natl. Hist. Nat. sér. 2, 24: 318. 1952.

Type:— VIETNAM: Prov. Khanh Koa, Nui Han Heo, pres de Nha Trang, Poilane 4855. Lectotype:—P (P 03232908!), Larsen et al. 1980; isolectotypes K (K000980293!), L (L0651585!).

Remaining syntypes:— VIETNAM: à 7 km de Nhatrang, route de Ninh-hoa, Poilane 4749; Nhatrang, réserve de Suoi-cat, Chevalier 39005, K !.

Scandent shrub to 8 m in length. Stems with scattered recurved prickles, glabrous, lenticellate. Stipules persistent, oblong, apex acuminate, 1 × 2 mm. Leaves with 4–5 pairs pinnae; 4–5 [–6] pairs leaflets per pinna; petioles 2–2.8 cm; leaf rhachis 8.5–14.5 cm, with recurved prickles in pairs and pinna insertion points, and usually scattered on the internodes; pinnae 4–7 cm; leaf rhachis, petiole, and pinna rhachis glabrous. Leaflets opposite to subopposite; the terminal leaflets elliptic, base oblique, apex obtuse to acute, 3.4–6.1 × 1.6–3 cm; lateral leaflets elliptic, base strongly oblique, apex obtuse to acute, 3.5–5.3 × 1.5–2.7 cm; all leaflets glabrous on both surfaces, glossy above; 2˚ veins anastomosing, 3˚ veins reticulate, veins visible on both surfaces, more prominent below, midvein sunken above, raised below. Inflorescence a panicle, terminal or axillary, to 30 [–40] cm; sometimes with scattered recurved prickles on axes and pedicels, these ca. 1 mm long; axes with (very) sparse pale orange pubescent hairs, glabresecent on basal peduncle; pedicels slender, 5–14 [–20] mm, articulated 0–1 mm below hypanthium, with few minute recurved prickles ca. 0.5 mm, very sparsely orange tomentose, hair denser at articulation. Bracts persistent, semicircular or triangular, ca. 1–1.5 × 1–2 mm, subglabrous or sparsely tomentose; bracteoles caducous, lanceolate, acuminate, 0.5–1 × 1–2 mm, sparsely tomentose. Flowers with a hypanthium 1–2 × 3 mm, glabrous or sparsely orange tomentose, sometimes at base only; lower calyx lobe 7–8 × 2–3 mm, other lobes 4–6 × ca. 2 mm; all lobes lobes sparsely orange tomentose on both surfaces, glabrescent. Median petal strongly reflexed backwards, 6–7 mm long, blade 3–4 × 3 mm, claw 2–3 × 1–2 mm; inner claw sparsely to moderately orange pubescent, petal otherwise glabrous. Upper lateral petals 7–10 mm long, blade ovate, 6–7 [–9] × 4 [–6] mm, glabrous, claw ca. 1 mm, with a few hairs on the inner surface, petal otherwise glabrous. Lower lateral petals 7–10 mm long, blade obovate, 6–7 × 3 mm glabrous, claw 1 mm long, with a few hairs on the inner surface, petal otherwise glabrous. Stamen filaments flattened, ca. 7 mm long, orange pubescent on inner face to the basal ½ of, or nearly entire length; anther 0.5–1 mm long. Ovary laterally somewhat inflated; 2–3 mm long, style ca. 5–12 mm long; ovary moderately orange pilose, style glabrous or subglabrous; stigma funnel-shaped, the rim papillate. Fruit unknown. Seeds unknown.

Distribution:—Endemic to Vietnam, vicinity of Nhatrang. ( Fig. 7)

Habitat and ecology:—Unknown.

Phenology:—Flowering September–October.

Preliminary conservation assessment:—Extent of Occurrence 131.115 km 2 = EN; Area of Occupancy 12.000 km 2 = EN.

Category assigned:—Endangered (EN). In the absence of further data, this is the appropriate assessment for this species. However, considering that there are only three herbarium specimens of this species known, and that the most recent of these was collected in 1932, it is likely that the species is more endangered than EOO and AOO values conclude, and may even be extinct. It is not possible to verify either of these possibilities without a detailed survey of the Nhatrang area.

A TAXONOMIC REVISION OF MEZONEURON

Phytotaxa 274 (1) © 2016 Magnolia Press • 15