Mezoneuron nitens (F. Mueller ex Bentham) R. Clark & E. Gagnon, 2016

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

17. Mezoneuron nitens (F. Mueller ex Bentham) R. Clark & E. Gagnon comb. nov.

Holotype:— AUSTRALIA: Queensland, Mt. Mueller, near Edgecombe Bay , 12 Deca. 1863, J. Dallachy s.n., MEL (MEL48871!)

Basionym. Pterolobium nitens F. Muell. ex Benth. Fl. Austral. 2: 279. 1864.

Synonym. Caesalpinia nitens (F. Muell. ex Benth.) Pedley. Austrobaileya 5: 99. 1997.

Scrambling shrub or liana, height unknown. Stems with scattered recurved prickles, older stems with spine-tipped tubercles and longitudinal corky ridges; sparsely whitish tomentose, glabrescent when older. Stipules persistent, triangular, 1 × 0.5–1 mm, sparsely to moderately pale orange tomentose. Leaves opposite to subopposite; 2–4 [–5] pairs pinnae; 2–4 (–5) pairs leaflets per pinna; petioles 1–2.5 cm; leaf rhachis 1.5–6 (–8) cm, with recurved prickles in pairs at the pinna insertion points, and sometimes scattered on the internodes; pinnae 1.5–5 cm, pinna rhachis with a single recurved prickle at the base of each leaflet, sometimes with scattered prickles on the internodes; leaf rhachis, petiole, and pinna rhachis sparsely to moderately pale orange to pale golden tomentose. Leaflets alternate to subopposite; the terminal leaflets elliptic to obovate, base oblique, apex rounded to retuse, (1.2–) 1.7–2.5 (–3) × (0.8–) 1.2–2.2 cm; lateral leaflets elliptic, base oblique, apex rounded to retuse, (0.9–) 1.7–2 × (0.7–) 1–1.5; all leaflets glabrous or sparsely appressed hairy above and below, hairs denser on midvein; 2˚ venation anastomosing, 3˚ venation reticulate, veins slightly raised on both surfaces. Inflorescence a terminal few-branched panicle, the racemes opposite, relatively short, to ca. 12 cm, with scattered recurved prickles up to 2 mm in length along entire length of peduncle; moderately golden to orange tomentose; pedicels 2–3 mm, articulated ca. 1 mm below the hypanthium, moderately golden or orange tomentose. Bracts persistent, triangular, 1 × 1 mm, sparsely pale orange tomentose; braceoles caducous, lanceolate, 2–4 × 1 mm, moderately pale orange tomentose on both surfaces. Flowers with a hypanthium 1–2 × 2–3 mm, sparsely golden or orange tomentose; lower lobe 5–6 [–7.5] × 2–3 mm; sparsely to moderately golden or orange tomentose; other lobes 4–5 × 2 mm; sparsely to moderately golden or orange tomentose, sometimes hairs only on central area and the margins, inner calyx glabrous. Median petal obovate, ca. 6 × 3 mm, blade ca. 4 mm long, claw ca. 1.5–2 mm long; circular patch of orange hair between claw and blade, the margins of the claw tomentose, outer surface glabrous. Upper lateral petals ca. 6 × 3–4 mm; blade obovate, ca. 4 mm long, claw ca. 2 mm long; claw tomentose on inner surface, petal otherwise glabrous. Lower lateral petals obovate, ca. 6 × 3–4 mm; blade ca. 5 mm long, claw ca. 1 mm long; claw tomentose on inner surface, petal otherwise glabrous. Stamen filaments flattened, [6–] 7–8 mm long, moderately pale orange tomentose on basal ½ on inner surface; anther 0.5–1 mm long. Ovary ca. 2 mm long, style ca. 7 mm long, both glabrous; stigma narrowly funnel-shaped, the rim papillate; 0.5–0.75 mm wide. Fruit unknown. Seeds unknown.

Distribution:—Endemic to Australia (Queensland). ( Fig. 20).

Habitat and ecology:—Notophyll forest; monsoon rainforest; on basalt/volcanic rock. Phenology:—Flowering October–December, fruiting time unknown.

A TAXONOMIC REVISION OF MEZONEURON

Phytotaxa 274 (1) © 2016 Magnolia Press • 33

Preliminary conservation assessment:—Extent of Occurrence 69,060.480 km 2 = LC; Area of Occupancy 76.000 km 2 = EN.

Category assigned:—Vulnerable (VU). Notophyll forests, which are characterised by a predominance of notophyll leaf sizes in the canopy layer (Webb 1958; www.wettropics.gov.au, accessed 2016), were subject to extensive logging prior to 1987, and are now heavily fragmented and restricted to inaccessible locations. These forests are subject to further threat from infection by the plant pathogen Phytophthora cinnamomi Rands , and degradation due to edge effects (www.wettropics.gov.au, accessed 2016). If M. nitens occurs only in notophyll forest, its habitat area is limited, and is subject to ongoing threats. Therefore, although the EOO of the species determines it as LC according to IUCN criteria, the higher threat category of Vulnerable is here assigned.