Wadithamnus artemisioides (Vierh. & O.Schwartz) T.Hammer & R.W.Davis, 2017

Hammer, Timothy A., Davis, Robert W. & Thiele, Kevin R., 2017, Wadithamnus, a new monotypic genus in Amaranthaceae, Phytotaxa 295 (2), pp. 173-184 : 180-182

Wadithamnus artemisioides (Vierh. & O.Schwartz) T.Hammer & R.W.Davis , comb. nov.

Basionym: Aerva artemisioides Vierhapper & Schwartz in Schwartz (1939: 43).

Type (lectotype here designated):— YEMEN. Hadramaut: Wadi Dhaurûten nordwestlich von Râs Farták., 07 March 1897, S. Paulay s.n. (WU-0066481!, image of the lectotype available at http://herbarium.univie.ac.at/database/detail.php? ID =306580). Syntypes: YEMEN. Hadramaut: Wadi Dhaurûten nordwestlich von Râs Farták., 07 March 1899, S. Paulay s.n. (WU-0066482!; WU-0066483!; WU-0066484!; HBG-503185!) ; Fût angeblich vom Djebel Rikbêt, 15° N 50° E, 25 February 1902, W. Hein s.n. (WU-0066485!) .

Description:— Shrub, up to 1 m high. Stems terete, white-tomentose with dendritic hairs, these sometimes contracted so appearing stellate. Leaves flat, alternate, grey-green, linear-oblong, obovate, narrowly oblanceolate to elliptic (4–40 × 2–12 mm), with dense, shortly dendritic hairs; base cuneate to long-attenuate, sessile to petiolate (petiole to 4 mm long); apex rounded. Synnflorescences terminal (loosely panicle-like), dense with 3(7)-flowered cymes, each cyme 1.5–8.0 mm long, 4–7 mm wide; inflorescence branches, bracts, bracteoles and flowers densely covered with short, white or pale grey, dendritic hairs; bracts ovate (1.0–1.4 × 0.7–1.1 mm); bracteoles ovate (1.1–1.4 × 0.6–1 mm). Flowers shortly pedicellate; tepals 6; outer tepals 2, oblong to broadly ovate (1.2–2.0 × 0.6–1 mm), adaxially glabrous, broadly membranous at margins; inner tepals 4, linear to narrowly lanceolate (1.0–1.5 × 0.4–0.6 mm), adaxially glabrous, narrowly membranous-margined. Staminal cup symmetrical, glabrous, 0.3–0.5 mm long; appendages present, triangular. Stamens 4; filaments glabrous, dilating slightly towards base, 0.2–0.4 mm long; anthers 0.20–0.35 mm long. Ovary globose-compressed (0.4–0.9 × 0.4–0.7 mm), glabrous; stigma sessile, capitate. Seeds globose (0.8 × 0.7 mm), pale brown, smooth and glossy.

Typification:— The protologue of Aerva artemisioides consisted of a detailed diangosis, the provenance (“In Arabien”), and the citation of specimens collected by W. Hein and S. Paulay. The collections by S. Paulay are mounted on four sheets at WU (one from 1897 and three from an expedition in 1899) and one sheet at HBG from the 1899 expedition; the collection from W. Hein is also deposited at WU and from 1902. These specimens are syntypes according to the Art. 9.5 of ICN ( McNeill et al. 2012). The earliest specimen collected by S. Paulay is preserved at WU (code 0066481) and it bears two pieces (detached flowering shoots) of the same plant, and a label reporting “ Wadi Dhaurûten nordwestlich von Râs Farták / 7 iii 1897 / leg. St. Paulay ” ; an additional label is marked “Typus!” and “! O. Schwartz 1934” (presumably in Schwartz’ handwriting). The label data matches those reported in the protologue, and the exsiccatum morphologically matches the diagnosis. As a consequence we here designate the WU-0066481 as the lectotype of the name Aerva artemisioides .

Distribution: — Wadithamnus artemisioides is restricted to near-coastal mountain ranges along the Arabian Sea coastline of the Arabian Peninsula.

Habitat: —Dry rocky slopes and wadi banks at 20 ‒ 650 m a.s.l.

Morphological notes: —Two subspecies are here recognized according to Miller & Nyberg (1994, sub Aerva ):

1. Leaves linear-oblong to linear-oblanceolate, 10–40 × 2–5 mm, long-attenuate at base into petiole or sessile ................................... ............................................................................................................................................................................. subsp. artemisioides

- Leaves elliptic to ovate, 4–25 × 5–12 mm, base cuneate, petiole short .................................................................. subsp. batharitica