Plants terrestrial, epipetric, or epiphytic, sometimes rheophytic; roots blackish, wiry, inserted radially or ventrally (Hymenasplenium), proliferous or non-proliferous; rhizomes usually odorless, rarely with the odor of wintergreen (e.g., Asplenium longissimum Blume), short- to long-creeping, or suberect, branched or more commonly unbranched, sometimes massive and forming a detritus-collecting basket (e.g., Asplenium nidus L.), bearing scales; rhizome scales lanceolate, clathrate, usually with  blackish cell walls and hyaline lumens, sometimes brown or golden-brown, the margins glandular or not, entire to dentate or  ciliate, without distinct pubescence; leaves green and not covered in mucilage during any stage of development, usually  monomorphic, sometimes hemidimorphic, spirally arranged or distichous and dorsal (Hymenasplenium), occasionally bulbiferous, the bulbils frequently at the leaf apex, in a distal pinna axil, or at the base of the lamina, leaves usually closely spaced, sparsely to densely scaly, occasionally pubescent, rarely glandular (e.g., Asplenium platyneuron (L.) Britton, Sterns & Poggenb.), also frequently with minute filiform proscales; petioles dull and greenish, gray, or brownish, or lustrous and castaneous, atropurpureous, or ebenous, the bases expanded in Hymenasplenium, otherwise not usually expanded, persistent or not, articulate to the rhizome in Hymenasplenium, otherwise not; petiolar vascular bundles two, each with C-shaped xylem, the bundles distally uniting to form a single X-shaped bundle; laminae soft-herbaceous to coriaceous, simple to 4-pinnate, the apex usually pinnatifid or non-conform, occasionally conform (e.g., Asplenium davisii Stolze), the leaf marginal cells usually not differentiated; pinna axes not articulate, among species with divided leaves the axes usually alate, with wings derived from a decurrent and thickened leaf margin, or the wings thin, fragile, and apparently derived from the rachis; rachis axes usually not sulcate adaxially, without a free central ridge; veins free or anastomosing, the areoles without free included veinlets, reaching the leaf margin or terminating before it, some species with a sub-marginal collecting vein, the vein endings forming hydathodes, or not differentiated; sori elongate, along one side of the vein, rarely paired back to back, and then usually not along the same vein, and if so then usually where groups of veins converge, indusiate; soral receptacle flat; indusia lateral, essentially flat, glabrous or sometimes glandular, opening along the lateral margin; sporangia with stalks one cell wide in the middle; spores monolete, non-chlorophyllous, brown, the perispore with sharp ridges or broad folds, sometimes echinulate, fenestrate, or reticulate; chromosome base numbers x = 36 (most species, e.g., Bir & Shukla, 1967; Walker, 1973a; Smith & Mickel, 1977), 38 (Hymenasplenium; Murakami, 1995), and 39 (Hymenasplenium; Kato & al., 1990; Murakami, 1995).

The Aspleniaceae family includes about 700 species in 10 genera of which the largest is Asplenium. Identification of the family is usually not difficult, the linear sori with lateral indusia that lie along one side of a vein usually being diagnostic. Those that appear to lie on both sides of a vein are probably the result of reduction or fusion of the lamina. 

Aspleniaceae are somewhat unusual considering their species-richness, in that they show strong patterns of diversification in both  temperate and tropical areas (rather than being predominantly tropical), and have approximately equal numbers of epiphytic and terrestrial species (Schneider & al., 2004a). These two major habit types—epiphytic versus terrestrial—are both scattered across the Aspleniaceae phylogeny, although there is some evidence that the most recent common ancestor of the Aspleniaceae crown clade was epiphytic (Schneider & al., 2004a). Our circumscription is identical to that of Smith & al. (2006), who include further information on this family.

Thulin, M. (1993) Aspleniaceae in Flora of Somalia 1: 13-14

Plants ferns, epiphytic or terrestrial, rhizomatous. Leaf blades  1-several times pinnately divided. Sori usually linear, borne on the costal side of veins, usually covered by an indusium (a flap of tissue that is an outgrowth of the epidermis.

The Aspleniaceae is now considered to include only two genera, Asplenium and Hymenasplenium, and 740 species. Many of the species now in Asplenium were once placed in different genera, such as Ceterach. This means that only one genus is now considered to be present in Somaliland, Asplenium.

 ©Trustees of the Royal Botanic Gardens, Kew. Reproduced with permission.  

Global distribution of Aspleniaceae. from GBIF.

Rothfels C.J., M.A. Sundue, L-Y. Kuo, A. Larsson, M. Kato, E. Schuettpelz & K.M. Pryer. (2012) A revised family-level classification for eupolypod II ferns (Polypodiidae: Polypodiales) Taxon 61: 515-533.

Smith A.R., K.M. Pryer E. Schuettpelz, P. Korall, H. Schneider & P.G. Wolf. (2006) A classification for extant ferns. Taxon 55: 705-731.