TABLE 1. Prominent morphological differences among Petalidium etendekaense, P in Petalidium etendekaense (Acanthaceae), a new species from Namibia, with notes on the taxonomic identity of P. glutinosum

TABLE 1. Prominent morphological differences among Petalidium etendekaense, P. glutinosum, and P. variabile.
CharacterP. etendekaenseP. glutinosumP. variabileIndumentum (vegetative parts)Tomentose-strigulose: usually few trichomes unevenly bifurcate or dendritic; scattered stalked glandular trichomes of various sizes in additionDensely strigulose; often with scattered short stalked glandular trichomes ca. of uniform size in additionDensely strigulose; often with scattered short stalked glandular trichomes ca. of uniform size in additionLamina (shape)Ovate or elliptic, rarely suborbicularNarrowly ovate, ovate or ellipticNarrowly ovate, elliptic, lanceolate sensu Lindley (Beentje 2016: 73), lanceolate, oblanceolate or obovateInflorescencesAxis and lateral branches becoming spiny with age; spines tapering, with a sharp or blunt tipAxis not spiny, or becoming spiny with age; spines needle-like with a blunt tip or spines taperingAxis not spiny, or becoming spiny with age; spines needle-like with a blunt tipBracts (shape)Oblanceolate or narrowly ellipticOblanceolate or lanceolate (sensu Lindley)Oblanceolate or lanceolate (sensu Lindley)Bracteoles (shape & reticulation)Narrowly ovate or ovate, narrowly elliptic or lanceolate; laterally compressed or notNarrowly ovate or ovate; laterally compressed or notElliptic-oblong (laterally compressed) or narrowly ovateBracteoles (indumentum, abaxially)Scattered stalked glandular trichomes of various sizes; sometimes sparsely puberulous in placesScattered stalked glandular trichomes of various sizes, usually interspersed with long simple irregular trichomes (appearing villose), sometimes sparsely striguloseDensely strigulose (similar to leaves); often interspersed with short stalked glandular trichomes of ca. uniform size, rarely with widely spaced long simple trichomes in additionCorolla (length with lobes straightened) (mm)22–2622–2616–21Corolla (ratio length of expanded vs. narrow portion)1:1.5–1.81:1.0–1.51:1.5–2.8Corolla (lobes orientation)Ascending spreadingUpper lobes in line with tube to sub-patent or ascending-spreading, other lobes patentUpper lobes in line with tube to sub-patent or ascending-spreading, other lobes patentCorolla upper lobes (shape)Ovate; connate for a third of the lengthOblong-ovate; connate for a third to half the lengthNarrowly ovate, to oblong-elliptic; connate for a third to half the lengthCorolla lateral lobes (shape)Oblong-ovateOblong-ovateObovate or ellipticCorolla anterior lobe (shape)Ovate, longer than broadBroadly obovate, suborbicular or spathulate, broader than longBroadly obovate or suborbicular, broader than longCorolla ratio anterior lobe vs. lateral lobes (width at base)1.0–1.5:1ca. 2:1ca. 2:1Corolla (lobes colour, adaxially)All lobes similarly colouredFront lobes differently coloured or shaded than othersFront lobes differently coloured or shaded than othersDistributionNamibia: northwest and west of Bergsig to the Skeleton Coast National Park and the Samanab River. Southwest and south of Bergsig to the northern side of the lower Huab River Valley.Namibia: from the Bergsig area southwards towards the Swakop River drainage area.Namibia: from the lower Huab River southwards to west central Namibia and in northern Namibia near Otavi and Grootfontein.