Steiropteris glabra A.R.Sm. & M.Kessler, 2017

Smith, Alan R. & Kessler, Michael, 2017, Prodromus of a fern flora for Bolivia. XXX. Thelypteridaceae, Phytotaxa 331 (1), pp. 1-34 : 30-32

Steiropteris glabra A.R.Sm. & M.Kessler , sp. nov. ( Fig. 5 )

Possibly most closely related to Steiropteris gardneriana , but differing by its smaller size; glabrous rachises, costae, and veins; indistinct, hairless sinus keels, or keels lacking; veins clearly meet the segment margins above the sinuses, thus contrasting with most other closely related species of subg. Steiropteris .

Type:— BOLIVIA. La Paz: Prov. Franz Tamayo, Parque Nacional Madidi, Sector Tanhuara parasando el Río Pelechuco , por el camino Telechuco/Apolo, 14º44’45”S, 68º56’48”W, 1834 m, A. F. Fuentes 14356, with J. Salas and R. Huasurco (holotype UC!; isotype MO) .

Plants terrestrial; stems arching to erect, caudices to ca. 7 × 0.8 cm, scales brown, ovate, glabrous or nearly so, 1.5–2.0 mm long and nearly as broad; leaves few, ca. 4 per plant, clustered, to ca. 45 cm long; blades thin-chartaceous, pinnate-pinnatifid, proximal 1–2 pinna pairs deflexed, about as long as next several pairs, apex confluent and pinnatifid; petioles stramineous, darkened at bases, to ca. 15 cm × 1–1.5 mm, glabrous, basally with scattered scales resembling the rhizome scales; rachises stramineous, glabrous abaxially and along sides, hairy only along the adaxial ridges, hairs hyaline, 0.5– 1.5 mm long, hyaline to yellowish, mostly 1–2 mm; pinnae sessile, subopposite throughout blade, to 8 × 1.7 cm, deeply pinnatifid to approximately 1 mm from costae, segments 3–4 mm wide; aerophores lacking at pinna bases; laminar buds lacking; veins to 7 pairs per segment, lowermost pair from adjacent segments meeting margins just above sinuses, sinus keels lacking or very weakly developed, lacking hairs; costal scales lacking abaxially, costae, veins, and segment margins glabrous abaxially, laminar surfaces between veins also glabrous, glands lacking, indument adaxially on costae and costules of spreading, acicular hairs mostly 0.5–1 mm, veins and surfaces between veins glabrous, or with rare hairs on veins; sori medial, round; indusia with hairs ca. 0.2 mm long, receptacles lacking glands.

Rang e:— Bolivia ( LP).

Ecology:— Rare, known only from the type; terrestrial; 1850 m.

Notes:— Steiropteris glabra is one of the smaller species in the genus, and is named for its glabrous blades, which are very atypical or unknown for other species in the genus. Steiropteris parva (A.R.Sm. & M.Kessler) Salino & T.E.Almeida , a still smaller species with conspicuous abaxial costal hairs, is also known only from Bolivia, from the Departments of Cochabamba, La Paz, and Santa Cruz ( Smith & Kessler 2008).

Figures

FIGURE 5. Steiropteris glabra. A. Habit. B. Medial pinna. C. Pinna segments, abaxial surface detail. D. Pinna segments, adaxial surface detail. E. Sorus. (All from the holotype: A.F. Fuentes 14356)