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| Petalidium kaokoense Swanepoel in Swanepoel, 2020. |
Abstract
Petalidium kaokoense, here described as a new species, is only known from the Hartmann Mountains and one other location on the inland plateau in the Kaokoveld Centre of Endemism, northwestern Namibia, where it grows on hillsides and mountain slopes. Diagnostic characters for P. kaokoense include the stout trunk on older plants, white bark, peeling on the younger branches in long, narrow strips, stellate trichomes, short inflorescences of racemoid dichasia with acute linear-oblanceolate or linear-lanceolate bracts, flowers with maroon corollas with the two upper lobes connate towards the base and the lower lobe with two yellow spots near the base. A comparison of some of the more prominent morphological features to differentiate between Petalidium kaokoense and its presumed close relative, the morphologically similar P. physaloides, is provided. Based on IUCN Red List categories and criteria, a conservation assessment of Vulnerable (VU D1) is recommended for the new species.
Keywords: endemism, flora, Hartmann Mountains, Kaokoveld, taxonomy, General
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| Figure 1. Petalidium kaokoense Swanepoel. A. Flowers and leaves; greyish leaves are still densely covered in trichomes. B. Flowering shoot; leaves almost glabrous. Photographs: W. Swanepoel. |
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| Figure 2. Petalidium kaokoense Swanepoel. Plant in natural habitat at the type locality, Hartmann Mountains, Namibia, growing as a shrub about 1 m tall. Photograph: W. Swanepoel. |
Petalidium kaokoense Swanepoel, sp. nov.
Diagnosis:— A woody shrub up to 1.2 m tall, morphologically similar to P. physaloides, from which it differs in having white bark on distal
branches peeling in long narrow strips (vs. fawn bark, not peeling); leaf apex rounded, obtuse or acute (vs. acute); flowers usually
in short racemoid dichasia (vs. inflorescences with flowers solitary or paired); inflorescence axis up to 60 mm long, sometimes
becoming spiny with age (vs. up to 310 mm long, not becoming spiny with age); anticous calyx lobe entire or indistinctly bifid (vs.
distinctly bifid); corolla with upper lobes connate over half their length, lateral and upper oblong, front one obovate (vs. upper lobes
almost free to base, all lobes ovate).
Etymology:— The specific epithet refers to the Kaokoveld in northwestern Namibia, a region forming part of the Kaokoveld Centre of Endemism (Van Wyk & Smith 2001, Craven 2009). This biogeographically well-defined region extends into southwestern Angola.
Wessel Swanepoel. 2020. Petalidium kaokoense (Acanthaceae), A New Species from Namibia. Phytotaxa. 468(3); 236-242. DOI: 10.11646/phytotaxa.468.3.1
