Megalastrum sparsipilosum R.C.Moran & J.Prado
Descripción
Megalastro pulverulento quoad folia usque ad 4 m longa et 4-pinnato-pinnatisecta simile, sed ab eo pinnarum rhachidibus costulis et venis subglabris vel abaxialiter sparsim pubescentibus glandulsisque differt.
Rhizomes to 0.4 m tall; leaves up to 4.6 m long; scales of the petiole base 20–50 × 2–3 mm, linear-lanceolate, spreading, golden to yellowish brown, denticulate throughout; laminae up to 3 m long, 4-pinnate-pinnatisect at base, medially 3-pinnate-pinnatisect; basal pinnae c. 1 m long, strongly inequilateral (elongated basiscopically); pinna rachises abaxially sparsely glandular, sparsely scaly, glabrous to sparsely pilose, the glands c. 0.1 mm wide, spherical, brownish, the scales to 2–3 × 0.2–0.5 mm, linear to lanceolate, appressed to slightly spreading, strongly denticulate, the hairs 1.0–1.5 mm long, c. 8-celled, adaxially glandular, densely pilose, the glands c. 0.1 mm wide, spherical, sessile, brownish, the hairs 1–2 mm long, 7–9-celled, spreading, light brown, the scales like those abaxially; costules abaxially sparsely glandular, sparsely pilose to nearly glabrous, sparsely scaly, the hairs 1.5–2.0 mm long, 8–12-celled, erect, the scales 0.8-1.0 mm long, strongly denticulate, appressed to slightly spreading, reddish brown, slightly shiny, the scales like those on the pinna rachises, proscales numerous, appressed, adaxially with indumenta like that of the pinna rachises; laminar tissue between the veins abaxially non-glandular, glabrous, adaxially sparsely glandular to nearly non-glandular; veins on both surfaces visible, abaxially non-glandular, sparsely pilose, the hairs 0.5–0.7 mm long, 3- or 4-celled, adaxially pilose, sparsely glandular, the hairs 1.0–2.0 mm long, 3–8-celled, spreading, the glands sessile, spherical; hydathodes evident; lamina margins sparsely ciliate to nearly glabrous, the hairs 0.2–0.4 mm long, 2–4-celled, nonglandular; indusia minute, fugacious, apparently consisting of a cluster of reddish proscales, c. 0.1 mm long, protruding from the centre of the sorus.A
Rhizomes to 0.4 m tall; leaves up to 4.6 m long; scales of the petiole base 20–50 × 2–3 mm, linear-lanceolate, spreading, golden to yellowish brown, denticulate throughout; laminae up to 3 m long, 4-pinnate-pinnatisect at base, medially 3-pinnate-pinnatisect; basal pinnae c. 1 m long, strongly inequilateral (elongated basiscopically); pinna rachises abaxially sparsely glandular, sparsely scaly, glabrous to sparsely pilose, the glands c. 0.1 mm wide, spherical, brownish, the scales to 2–3 × 0.2–0.5 mm, linear to lanceolate, appressed to slightly spreading, strongly denticulate, the hairs 1.0–1.5 mm long, c. 8-celled, adaxially glandular, densely pilose, the glands c. 0.1 mm wide, spherical, sessile, brownish, the hairs 1–2 mm long, 7–9-celled, spreading, light brown, the scales like those abaxially; costules abaxially sparsely glandular, sparsely pilose to nearly glabrous, sparsely scaly, the hairs 1.5–2.0 mm long, 8–12-celled, erect, the scales 0.8-1.0 mm long, strongly denticulate, appressed to slightly spreading, reddish brown, slightly shiny, the scales like those on the pinna rachises, proscales numerous, appressed, adaxially with indumenta like that of the pinna rachises; laminar tissue between the veins abaxially non-glandular, glabrous, adaxially sparsely glandular to nearly non-glandular; veins on both surfaces visible, abaxially non-glandular, sparsely pilose, the hairs 0.5–0.7 mm long, 3- or 4-celled, adaxially pilose, sparsely glandular, the hairs 1.0–2.0 mm long, 3–8-celled, spreading, the glands sessile, spherical; hydathodes evident; lamina margins sparsely ciliate to nearly glabrous, the hairs 0.2–0.4 mm long, 2–4-celled, nonglandular; indusia minute, fugacious, apparently consisting of a cluster of reddish proscales, c. 0.1 mm long, protruding from the centre of the sorus.A
Ejemplar revisado
Chiapas: Rayón, Selva Negra 10 km above Rayón Mezcalapa along road to Jitotol, [17°10′ N, 92°10′ W], 1700 m, 25 Jan. 1973, Breedlove 32364 (F, NY); La Independencia, third ridge along logging road from Las Margaritas to Campo Alegre, [15°20′ N, 92°34′ W], 2300 m, 18 Feb. 1973, Breedlove 33687 (F, NY); SE side of Volcán Tacaná above Talquian, 2200 m, 16 Jan. 1973, Breedlove 31677 (F, NY); Motozintla de Mendoza, 45–50 km NE of Huixtla along rd to Motozintla, [15°22′ N, 92°13′ W], 1900 m, 17 Nov. 1971, Breedlove & Smith 22622 (F, MO, NY); Hidalgo: Chapulhuacán, [21°10′ N, 98°54′ W], 0 m, 27 Nov. 1937, Kenoyer 720 (F); Chapulhuacán, [21°10′ N, 98°54′ W], 0 m, 23 Nov. 1937, Kenoyer 689 (F); Puebla: Tehuacán area, above Teotitlan del Camino on the road to Huautla, [18°28′ N, 97°23′ W], 0 m, 3 Aug. 1961, Smith et al. 4139 (F, US); Teziutlán, Agua de Obispo, [19°48′ N, 97°21′ W], 1400 m, 28 Jan. 1970, Ventura A 399 (MICH, NY); San Marcos: between Finca El Porvenir and Loma Corona, 9 miles W of el Porvenir, SW facing slopes of Volcán Tajumulco, [15° 01′ N, 91°55′ W], 0 m, 14 March 1949, Steyermark 37750 (F, US); vic. of Tajumulco, NW slopes of Volcán Tajumulco, [15°01′ N, 91°55′ W], 0 m, 28 Feb. 1940, Steyermark 36867 (F, US); Veracruz: Huayacocotla, El Salto, [20°39′ N, 98°26′ W], 1650 m, 13 March 1980, Ramírez 645 (F); 10 km de la carretera Teziutlán-Nautla, [20°13′ N, 96°46′ W], 0 m, Dec. 1945, Sánchez 345 (US).A
Elevación
1400 – 2300 mA
Tipo de vegetación
Bosque de neblina/mesófiloA
Categoría IUCN
No incluidaB
Categoría NOM-059-SEMARNAT-2010
No incluidaC
Discusión taxonómica
Megalastrum sparsipilosum is characterised by large leaves (to 4.5 m long), laminae sparsely pilose on both surfaces, and strongly denticulate scales on the axes. It resembles M. heydei and M. pulverulentum in the large size and dissection of the leaves but differs from the former by longer hairs on both surfaces of the pinna rachises (these hairs only 0.1-0.2 mm long in M.heydei), and from the latter species by sparsely pilose pinna rachises, costules, and veins on abaxial surface of the laminae (versus densely pubescent in M. pulverulentum).
The specific epithet sparsipilosum refers to the sparse pubescence on the abaxial surface of the laminae, especially when compared to M. pulverulentum. Specimens of Megalastrum sparsipilosum from Chiapas and Guatemala are more sparsely pubescent than those from Honduras. In some, it is difficult to find hairs on the lamina margins — a characteristic unusual in the genus. The variation in pubescence does not appear to correlate with other characters and is therefore interpreted here as variation in a single species.
A
The specific epithet sparsipilosum refers to the sparse pubescence on the abaxial surface of the laminae, especially when compared to M. pulverulentum. Specimens of Megalastrum sparsipilosum from Chiapas and Guatemala are more sparsely pubescent than those from Honduras. In some, it is difficult to find hairs on the lamina margins — a characteristic unusual in the genus. The variation in pubescence does not appear to correlate with other characters and is therefore interpreted here as variation in a single species.
A