Mickel, John T. & Smith, Alan R. 2004. The pteridophytes of Mexico. Mem. New York Bot. Gard. 88: 1-1054.
Aspleniaceae
Species Description - Roots fibrous, not proliferous; rhizomes suberect; rhizome scales brown, clathrate, 3–4 x 1–1.3 mm, entire; fronds clumped, mostly 12–45 cm long; stipes green to brownish green, 4–18 cm x 1–2 mm, 1/3–1/2 of frond length, glabrous or with rare to sparse scales 0.8–1 mm long, non-alate or very narrowly alate; blades thick-chartaceous to subcoriaceous, narrowly deltate, 11–40 x 3–12 cm, 1-pinnate, apices pinnatifid, not proliferous; rachises similar to stipes, glabrous, with wings 0.5 mm wide; pinnae narrowly lanceolate, 12–20 pairs, 2–6 x 0.5–1.2 cm, stalked 1–4 mm, bases narrowly to broadly cuneate, apices attenuate to obtuse, margins sharply bidentate; indument abaxially of rare to scattered hairlike, clathrate scales 0.5–1 mm long, especially in pinna axils, also with scattered clavate hairs on and between veins; veins obscure, 1-forked, tips evident adaxially; sori 4–8(–12) pairs per pinna; indusia 3–4 x 0.3–0.5 mm, margins entire; spores reniform, tan, 64 per sporangium; 2n=144 (Jam).
Type. Jamaica. Swartz s.n. (S; isotype B).
Unverified, Doubtful, or Mistaken Reports. Qro (Takaki s.n., ENCB, cited by Di´az-Barriga & Palacios-Rios, 1992, and Arregui´n et al., 2001, but specimen not found, and the identification is suspect). Asplenium macilentum Kunze ex Klotzsch is sometimes regarded as distinct (e.g., by Adams (in Davidse et al., 1995: 309), but we regard its placement as problematic (see comments under A. monodon). Asplenium levyi, treated as a synonym of A. macilentum by Adams, differs from A. auritum only its slightly more coriaceous segments and more nearly entire pinnae. Another synonym is A. plumbeum Christ, also treated as a synonym of A. macilentum by Adams. The A. auritum complex, which in Mexico includes A. auritum, A. cuspidatum, A. monodon, and A. sphaerosporum, needs modern biosystematic study. Morton and Lellinger (1966) treated this complex as two species, A. auritum (with 6 varieties) and A. cuspidatum (with 5 varieties). Until more detailed morphological, cytological, and isozymic studies are made, the division of this complex into taxa based mainly on blade and pinna dissection, blade texture, and spore type will have to stand. The blade dissection series seen in the auritum/cuspidatum complex varies from 1-pinnate in A. auritum, to deeply pinnatepinnatifid to 2-pinnate with dentate segments in A. cuspidatum, to 2-pinnate-pinnatifid to 3-pinnate in A. fragrans. This series is roughly paralleled in the dissection series seen in A. monodon (blades 1-pinnate with superior auricles to pinnate-pinnatifid proximally) to A. sphaerosporum (2-pinnate). Asplenium monodon and A. sphaerosporum differ from the first three species in having globose, blackish spores numbering only 32 per sporangium (indicating an apogamous life cycle) compared with the tan to brown, reniform spores, numbering 64 per sporangium in sexual diploids and tetraploids. All five of these species are basically epiphytic (occasionally epipetric) and occur at somewhat different, but overlapping, elevations in Mexico. Asplenium auritum is found at 100–800 m, A. cuspidatum at (350–)800–2500 m, A. fragrans at (300–)1500–3050 m, A. monodon at 100–1600(–2300) m, and A. sphaerosporum at 650–2700 m.