This is a family of five genera, viz., Aulacopilum Wils., Erpodium (Brid.) Brid., Solmsiella C. Müll., Venturiella C. Müll, and Wildia (C. Müll.) Broth. A sixth genus, Microtheciella Dix., was segregated into the family Microtheciellaceae (Miller & Harrington 1977). Solmsiella is often combined with Erpodium (Crum 1972, Touw 1992, Vital 1980). Stone (1997) recently combined Aulacopilum, Wildia, and Venturiella with Erpodium, thus reducing the family to a single variable genus. Only Erpodium and Solmsiella are present in Central America.

The Erpodiaceae are usually placed in the diplolepidous-series of mosses near the Orthotrichaceae. Most Erpodiaceae are eperistomate, but E. coronatum (Hook. & Wils.) Mitt. has a peristome reduced to an irregular membrane, and Venturiella sinensis (Vent. ex Rabh.) C. Müll. and Wildia solmsiellacea C. Müll. & Broth. have 16 narrowly triangular peristome teeth. Noguchi (1952) and Edwards (1979) have shown that the peristome in Venturiella is endostomial in position with somewhat stronger deposition on the outer (dorsal) surface than the inner (ventral) surface, and that its peristomial formula is 4:2:2. Edwards (1979) thought this peristome could be haplolepidous. On the basis of such a peristomial interpretation as well as rbcL-gene sequences Goffinet et al. (1998) placed the Erpodiaceae in the Haplolepideae, La Farge et al. (2000) put the taxon in the Pottiales, and Buck & Goffinet (2000) transferred the family to the Dicranales.

As noted by Edwards (1979), however, some members of the Orthotrichales have the same peristomial formula and type of secondary thickening as the Venturiella peristome. Furthermore, the E. coronatum peristome-type, a reduced irregular membrane, is also seen in the Bryaceae (e.g., Mielichhoferia or Brachymenium). This type of peristome reduction, although probably analogous in the Erpodiaceae and Bryaceae, has no counterpart in the Haplolepideae and so argues for placing the Erpodiaceae in the Diplolepideae. In our view the confidence levels of the rbcL gene analyses (e.g., LaFarge et al. 2000 assign Bootstrap values to their analyses of 51, 52, <50) are so low that these data are inconclusive. Finally, the presence of rhizoidal initials clustered at the abaxial leaf insertion (see Noguchi 1952, fig. 2 and Stone 1982, fig. 1 a–b) is a characteristic feature of Diplolepideous mosses (see Hedenäs 1987).