Adiantum squamulosum J.Prado & A.R.Sm., Amer. Fern J.

Kessler, Michael, Smith, Alan R. & Prado, Jefferson, 2017, Prodromus of a fern flora for Bolivia. XXVII. Pteridaceae, Phytotaxa 332 (3), pp. 201-250 : 239

Adiantum squamulosum J.Prado & A.R.Sm., Amer. Fern J. 92(2): 105(–107), fig. 1. 2002.

Range: — Bolivia (BE, PA); endemic.

Ecology: —Rare (known from only 3 collections), terrestrial in forests; 150–250 m.

Notes: —For additional comments and characterization, see Prado & Smith (2002). A member of the Adiantum tetraphyllum group (Huiet et al. in prep.), with rhizomes stout, short-creeping, nodose, copiously scaly rachises, and more numerous pinnules (41–46 pairs per pinna) than related species. Blades 2-pinnate, (3–)4–9 pairs of lateral pinnae; pinnules ca. 2 times longer than wide, with scales on veins on both surfaces; indusia oblong, bearing lanceolate scales with pectinate bases.

Adiantum terminatum Kunze ex Miq., Verslagen Meded. Vier. Kl. Kon. Ned. Inst. Wetensch. Letterk. Schoone Kunsten 1842: 187 . 1843.

Range: —Southern Mexico to Panama; Colombia to Trinidad, Guianas, and Bolivia (BE, CO, LP, PA, SC); Brazil.

Ecology: —Common in lowland wet forests; 150–600(–1200) m.

Notes: —Most closely related to A. humile , in the A. tetraphyllum group, and notable especially by the relatively small frond size, pinnules abaxially with long, septate, brown hairs, adaxially glabrous, and by the finely serrulate margins of sterile pinnules. Rhizomes short-creeping, nodose; rachises sparsely scaly, scales narrowly lanceolate; blades with 2–4 pairs of lateral pinnae; pinnules ca. 3 times longer than wide, 8–15 pairs per pinna, reduced toward pinna bases and apices, distal pinnules less than half the size of largest ones; indusia with reddish brown hairs.

Buchtien 1099 (UC) is similar to A. terminatum and A. humile in having sterile pinnules varying from oblong to round, but it differs by its regularly dentate sterile pinnules, sparsely scaly laminae abaxially (the scales each with a pectinate base), and oblique idioblasts in the laminar tissue visible on both surfaces. This collection might represent a new species, but because it is sterile, we are choosing not to describe it at this time (awaiting further collections to confirm its distinctness).