Steiropteris alstonii Salino & A.R.Sm., 2018

Salino, Alexandre & Smith, Alan R., 2018, Steiropteris alstonii (Thelypteridaceae), a new species from Colombia, and some new combinations in the family, Phytotaxa 340 (2), pp. 175-180 : 176

Steiropteris alstonii Salino & A.R.Sm. , sp. nov. ( Figs. 1–2 )

This is one of the smaller species of Steiropteris , lacks aerophores, and has inconspicuous false veins. Steiropteris alstonii is somewhat similar to S. gardneriana in habit but differs by having smaller pinnae 2–4.1 × 0.7–1.65 cm (versus 4.5–12 × 1.6–2.7 cm), pinnae slightly undulate to incised to 1/3 or rarely to 1/2 their width (versus 2/3 to 3/4), veins 2–4 pairs per segment (versus 6–10 pairs), and scattered, adpressed, stipitate-capitate glandular hairs (0.08–0.15 mm) mainly on the costae (versus costae abaxially with setose hairs).

Type: — COLOMBIA. Department of Nariño: between Paramo and Barbacoas, 500 m, 07 May 1939, A. H. G. Alston 8464 (holotype BM 000592158, isotype MO 3765956).

Plants terrestrial. Rhizomes erect; rhizome scales 2–3 mm long, lanceolate with long-acuminate apices, castaneous, with acicular hairs. Fronds 23–42 cm long, monomorphic; petioles 10–21 cm long, 0.7–1.25 mm diam., slightly sulcate adaxially, sparsely scaly at bases, scales like those of rhizomes, moderately to densely covered by acicular, arcuate hairs 0.2–0.3 mm long in the adaxial grooves; laminae 13–21 cm long, elliptic, chartaceous, 1-pinnate-pinnatifid, each with a confluent, pinnatifid, caudate apex; rachises pilose like the petioles, but with hairs on all surfaces; aerophores absent; buds absent; pinnae 2–4.1 × 0.7–1.65 cm, 9–16 pairs, alternate to opposite, arcuate to ascending, the proximal pair reduced to 60% of the size of the next distal pair, pinnae slightly undulate to incised to 1/3 (rarely to 1/2) their width, sessile in the distal half of laminae and stalked 1 mm in the proximal half, lanceolate with apices rounded to acute, bases truncate to slightly cordate in the proximal pinnae; abaxial surfaces with scattered, adpressed, stipitate-capitate glandular hairs, these 0.08–0.15 mm long, mainly on costae, costules, and veins; adaxial surfaces with acicular hairs 0.2–0.3 mm long only on the costae; segments 2.9–3.9 mm wide, arcuate, entire, obtuse to acute apically; veins 2–4 pairs per segment, unbranched, with clavate tips adaxially, the basal vein pairs from adjacent segments connivent at sinuses or meeting margins just above the sinuses, distal vein of each pair arising from a costule or costa near the costule; sinus keels slight developed and hairy. Sori round, medial; indusia persistent, round or round-reniform, with setose hairs; sporangia glabrous.

Distribution and habitat: — Steiropteris alstonii is known only from the type collection in Colombia, where it apparently grows in rain forests on steep banks at ca. 500 m.

Etymology: — Steiropteris alstonii is named for Arthur Hugh Gart Alston (1902–1958), a British pteridologist and Selaginella expert who worked at the Natural History Museum, London (BM Herbarium) and also collected the type specimen.

Notes: —In Bolivia there are two small endemic species of Steiropteris : S. parva ( Smith & Kessler 2008: 57) Salino et al. (2015: 47) and S. glabra Smith & Kessler (2017: 30) . The former has even smaller fronds 6.5–10 cm long (versus 23–42 cm) and conspicuous acicular hairs 0.3–2.2 mm long on costae and veins abaxially (versus scattered, adpressed, stipitate-capitate glandular hairs, these 0.08–0.15 mm long on costae, costules, and veins abaxially). The latter species has rhizomes forming caudices to 7 cm long (versus rhizomes erect, but not forming caudices), larger, sessile pinnae 8 × 1.7 cm long (versus 2–4.1 × 0.7–1.65 cm), that are deeply pinnatifid to approximately 1 mm from the costae (versus pinnae slightly undulate to incised to 1/3, rarely to 1/2). In addition, there is no overlap in the area of occurrence in Colombia with S. gardneriana because that species occurs only in the region of Magdalena and S. alstonii only in the Department of Nariño.

Figures

FIGURE 1. Image of the holotype of Steiropteris alstonii (A.H.G. Alston 8464, BM).

FIGURE 2. Steiropteris alstonii. A. Detail of the abaxial side of segments showing venation, false veins and sori. B. Detail of the setose indusium.