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Issue: Vol. 728 No. 1: 11 Nov. 2025
Type: Article
Published: 2025-11-11
DOI: 10.11646/phytotaxa.728.1.2
Page range: 17-30
Abstract views: 165
PDF downloaded: 110

Petalidium sebrabergense (Acanthaceae), a new species from Namibia

Independent Researcher, P.O. Box 21168, Windhoek, Namibia; H.G.W.J. Schweickerdt Herbarium, Department of Plant and Soil Sciences, University of Pretoria, Pretoria, 0002 South Africa; Ongava Research Centre, Private Bag 12041, Windhoek, Namibia
H.G.W.J. Schweickerdt Herbarium, Department of Plant and Soil Sciences, University of Pretoria, Pretoria, 0002 South Africa; South African National Biodiversity Institute, Private Bag X101, Pretoria, 0001 South Africa
anorthosite endemism Epupa flora Kaokoveld Centre of Endemism Kunene Igneous Complex Kunene Region Kunene River Ruellieae Swartbooisdrif taxonomy ultramafic rocks Zebra Mountains Eudicots

Abstract

Petalidium sebrabergense, first collected in May 2024 and easily mistaken for P. cirrhiferum, is described here as a new species. It is a range-restricted species, only known from Namibia’s Zebra Mountains, within the Kaokoveld Centre of Endemism. It typically grows on plains, hillsides, and along ephemeral riverbeds and drainage lines, primarily in soils derived from anorthosite and gabbro of the Kunene Igneous Complex. Key distinguishing features for P. sebrabergense include the pale green appearance of the plants, vegetative parts with indumentum of dense, simple, multi-cellular stalked glandular trichomes, frequently interspersed with widely spaced eglandular simple and bifurcate trichomes, often with some leaves additionally bearing sparsely branched dendritic trichomes. The flowers are borne in racemose dichasia and are notable for having the corolla lobes lilac or mauve, with both sides concolorous. A comparison of key morphological features distinguishing P. sebrabergense from P. cirrhiferum, its closest look-alike, is provided. Brief comparisons are also made with P. huillense, P. subcrispum, and P. welwitschii, species with which it can be confused, particularly in herbarium specimens. Based on IUCN Red List criteria, a provisional conservation status of Critically Endangered (CR) is recommended for the new species.

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How to Cite

Swanepoel, W. & Wyk, A.E.V. (2025) Petalidium sebrabergense (Acanthaceae), a new species from Namibia. Phytotaxa 728 (1): 17–30. https://doi.org/10.11646/phytotaxa.728.1.2