Cyathea atrocastanea Labiak & Matos (2009: 476)

Lehnert, Marcus, 2016, A synopsis of the exindusiate species of Cyathea (Cyatheaceae-Polypodiopsida) with bipinnate-pinnatifid or more complex fronds, with a revision of the C. lasiosora complex, Phytotaxa 243 (1), pp. 1-53 : 11

18. Cyathea atrocastanea Labiak & Matos (2009: 476) . Type:— BRAZIL. Espírito Santo: Santa Teresa, Estação Biológica de Santa Lúcia—Museu de Biologia Melo Leitão, 19°53'48"S, 40°36'11"W, 600 m, 11 July 2007, P.H. Labiak et al. 4008 (holotype UPCB n.v., isotypes RB-804639!/-804640!, SP n.v.).

Trunks to 3 m tall, to 8 cm diameter. Fronds to 3 m long. Petioles to 1 m long, turberculate to muricate, with dense castaneous scurf consisting of congested trichomidia and squamules. Laminae to 200 × 160 cm, bipinnate-pinnatifid, apices gradually reduced. Costules and midveins abaxially glabrescent, with scattered trichomidia ca. 0.2 mm long, and flattish, ovate to ovate-lanceolate, reddish brown scales, 0.4–0.8 × 0.3–0.4 mm. Segments rounded or obtuse, margins crenulate, fertile veins forked, sori proximal to subproximal, exindusiate, paraphyses longer than the sporangia.

See Labiak & Matos (2009) for full description and illustration.

Distribution and habitat:— Eastern Brazil, in montane forests at 600– 800 m.

Remarks: — Cyathea atrocastanea is very similar to Cyathea lasiosora , especially the Bolivian populations, which have a similar weak pubescence. Cyathea atrocastanea differs in the soral position (proximal to subproximal vs. ± medial in C. lasiosora ), the shape of laminar squamules (predominantly ovate and flat vs. broadly to narrowly lanceolate and bullate) and the absence of crenate segment margins (subentire vs. subentire to strongly crenate in C. lasiosora ). The gradually reduced laminar apices of C. atrocastanea are not utile for distinguishing both species because the apices of C. lasiosora vary between being abruptly to gradually reduced, correlating with the provenance (mainly gradually reduced in Andean populations, abruptly reduced in northern Amazonian populations).