Species New to Science's Journal

[Botany • 2019] Euphorbia rimireptans (Euphorbiaceae, Articulofruticosae) • A New Species from the Skeleton Coast, Namibia

Euphorbia rimireptans Swanepoel, R.W.Becker & Alma Möller

in Swanepoel, Becker, Mӧller & de Cauwer, 2019.

DOI: 10.11646/phytotaxa.414.4.2

Abstract

Euphorbia rimireptans, here described as a new species, is known only from the northern part of the Skeleton Coast (part of the Namib Desert) in the Kaokoveld Centre of Endemism, northwestern Namibia. These perennial shrublets grow on rocky outcrops of latite under harsh desert conditions. Diagnostic characters for E. rimireptans include the procumbent, sometimes pendant habit, the soft, rubber-like terete or slightly tapering branches that are curved or ± straight, frequently orientated in the same direction from the base, and the glabrous or sparsely hairy capsule, which releases verrucose ovoid seeds. A comparison of some of the more prominent morphological features to differentiate between E. rimireptans and its possible nearest relative, E. giessii, is provided.

Keywords: endemism, flora, Kaokoveld Centre of Endemism, latite, Namib Desert, taxonomy

FIGURE 2. Euphorbia rimireptans. A. Staminate cyathia. B. Pistillate cyathia, in different stages of development. C. Capsule. D. Inflorescences, staminate plant. Photographs by W. Swanepoel.

FIGURE 1. Habit of Euphorbia rimireptans. A. Pendant. B. Procumbent, all branches orientated in one direction, showing grey base. C. Procumbent, branches intertwined. Photographs by W. Swanepoel.

FIGURE 4. Euphorbia rimireptans plant (foreground, centre) in its natural habitat. Photograph by W. Swanepoel.

Euphorbia rimireptans Swanepoel, R.W.Becker & Alma Möller sp. nov.

Diagnosis:— Succulent shrublet up to 0.5 m in its greatest diam., similar to E. giessii, from which it differs in being procumbent, sometimes pendant (vs. erect, up to 0.8 m high); branches, shorter and thinner (up to 0.5 m long, 2.8–6.0 mm diam.), soft, rubber-like, terete or only slightly tapering [vs. longer and thicker (up to 0.8 m long, 4–12 mm diam.), rigid, firm, tapering]; leaf lamina not panduriform, of uniform thickness, glabrous (vs. somewhat panduriform, thickened towards apex, densely hairy at base adaxially); bracts dissimilar to the leaves, hairy adaxially at base only, otherwise glabrous (vs. bracts similar to the leaves, hairy adaxially); gland shape mostly variable on each involucre, oblong, oblong-elliptic, elliptic, reniform, ovate or flabellate (vs. gland shape uniform on each involucre, oblongelliptic, elliptic or sub-circular); staminate flowers with filaments glabrous, shorter (0.4–0.8 mm long), anther theca pale yellow [vs. filaments glabrous or with long hairs, longer (0.9–1.2 mm long), anther theca pale green]; capsule glabrous or sparsely hairy, rarely dotted, pedicel ± 0.6 mm diam. (vs. sparsely to densely hairy, seldom glabrous, conspicuously dotted, pedicel ± 1.1 mm diam.); seed verrucose.

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Etymology:— The specific epithet is derived from Latin and refers to the habit of Euphorbia rimireptans: ‘rimireptans’ = creeping from rock fissures.

FIGURE 3. Euphorbia rimireptans plant that was pressed as the type specimen, showing subtuberous root. Photograph by W. Swanepoel.

Wessel Swanepoel, Rolf W. Becker, Alma Mӧller and Vera de Cauwer. 2019. Euphorbia rimireptans (Euphorbiaceae, Articulofruticosae), A New Species from the Skeleton Coast, Namibia. Phytotaxa. 414(4); 165–173. DOI: 10.11646/phytotaxa.414.4.2