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| Petalidium matupaense Swanepoel & A.E.van Wyk, in Swanepoel et van Wyk, 2026. |
Abstract
Petalidium matupaense, first collected in May 2019, is here described as a new species. It is a range-restricted species, only known from the mountainous region bordering the Cunene River in southwestern Angola in the Kaokoveld Centre of Endemism. The species grows amongst boulders on hillsides of the Kunene Igneous Complex, along ephemeral riverbeds and in intermontane valleys. Diagnostic characters for P. matupaense include its slender stems and the dense white indumentum of mainly short-stalked dendritic trichomes on the vegetative parts (glabrescent with age) and inflorescences, giving a matted appearance. The flowers are distinctive in having all lobes similarly coloured adaxially, carmine, peach, vermillion (orange-red), or mauve, the anterior lobe with two yellow narrowly triangular nectar guides, and all lobes discolorous in being abaxially paler or cream-brown. A comparison of key morphological features distinguishing Petalidium matupaense from P. cirrhiferum and P. sebrabergense, its morphologically most similar relatives, is provided. Based on IUCN Red List criteria, the species is provisionally assessed as Endangered (EN).
Eudicots, Cunene Province, endemism, Kunene Anorthosite Complex, Oncocua, Ruellieae, Serra Matupa, taxonomy, ultramafic rocks, Zebra Mountains
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| Petalidium matupaense. A, B. Flowering shoots with foliaceous bracts, bracteoles and flowers; axes and bracts densely clothed in a white, matted indumentum. C. Mature foliage leaves becoming glabrescent and appearing greenish in contrast to the dense whitish indumentum of a flowering shoot bearing foliaceous bracts and persistent bracteoles. Photographs by W. Swanepoel. |
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| Petalidium matupaense. Morphology of flowers. A–C. Flowers in front view. Colour of corolla lobes varies adaxially: carmine, peach, vermillion (orange-red), or mauve. D. Flower with bracteole in side view. Corolla lobes abaxially paler or cream-brown. E. Flower and bracteoles viewed from below. F. Flower in oblique side view, with leaves, foliaceous bracts, and bracteoles; note dense white indumentum of leaves and bracts. Photographs by W. Swanepoel. |
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| Petalidium matupaense. Habitat and habit. A. Dwarf shrub ca. 900 mm tall with long, slender stems. B. Dwarf shrub with flowers ca. 700 mm tall, growing among dark leucotroctolite rocks in a seasonal drainage line; distal flower-bearing stem portions with foliaceous bracts and appear white due to a dense, matted indumentum consisting predominantly of short-stalked dendritic trichomes. C. Dwarf shrub ca. 700 mm tall with mostly older glabrescent leaves, growing in whitish anorthosite-derived soil. Photographs by W. Swanepoel. |
Petalidium matupaense Swanepoel & A.E.van Wyk, sp. nov.
Diagnosis:—A woody dwarf shrub up to 1.2 m tall, morphologically most similar to Petalidium cirrhiferum and P. sebrabergense, differing by having the indumentum on new vegetative growth and inflorescences similar, matted (vs. indumentum on vegetative parts and inflorescences dissimilar [P. cirrhiferum & P. sebrabergense], matted or floccose [P. cirrhiferum], scattered [P. sebrabergense]), mainly consisting of dendritic trichomes (P. matupaense & P. cirrhiferum) (vs. mainly consisting of stalked glandular trichomes [P. sebrabergense]); bracteoles with all dendritic trichomes short-stalked, not visible to the naked eye (vs. some very long-stalked, up to 5 mm long, clearly visible to the naked eye [P. cirrhiferum]); flowers with corolla lobes adaxially carmine, peach, vermillion (orangered) or mauve (vs. heliotrope, magenta or purple-red [P. cirrhiferum], lilac or mauve [P. sebrabergense]).
Etymology:—The specific epithet refers to Serra Matupa [Matupa Mountain] in southwestern Angola, which is the type locality.
WESSEL SWANEPOEL and ABRAHAM E. VAN WYK. 2026. Petalidium matupaense (Acanthaceae), A New Species from Angola. Phytotaxa. 784(2); 188-200. DOI: doi.org/10.11646/phytotaxa.784.2.4 [2026-11-12]
