Flora of North America species comparison

Sanionia uncinata is the only North American species of the genus with a perfect peristome and usually curved and horizontal capsules. When the shoot is examined from the dorsal side, the leaves of normally developed shoots appear to be combed, with leaves pointing stiffly, obliquely forwards-outwards; weak plants growing in relatively dry situations on rocks or tree stems may have less distinctly combed leaves that are sometimes non-plicate or almost so. From all except S. symmetrica, S. uncinata is separated by the structure of the alar and supra-alar cells. Sanionia uncinata is usually somewhat smaller and more regularly pinnate than S. orthothecioides.

The identity of Hypnum uncinatum var. plumulosum Bruch & Schimper [Drepanocladus uncinatus var. plumulosum (Bruch & Schimper) Warnstorf] is somewhat unclear because no type material seems to be extant; most of the North American material referred to this name belongs to typical Sanionia uncinata. Type material of Hypnum (Harpidium) moseri Kindberg (Hypnum uncinatum subsp. moseri) could not be found among material of Kindberg in Stockholm. However, since this taxon should differ from S. uncinata mainly in its non-plicate leaves, and non-plicate leaves occur in some expressions of the latter, it is unlikely to represent a separate taxon.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species 4 (4 in the flora).

Sanionia is characterized by its well-developed hyalodermis, plicate leaves, hyaline, thin-walled, inflated alar cells forming a transversely triangular or ± isodiametric group, sometimes prorate distal cell ends on the abaxial lamina, and, except in the strongly specialized S. nivalis, very long-acuminate inner perichaetial leaves. Except for S. nivalis, the species generally occur in drier habitats than members of, for example, Drepanocladus, Scorpidium, or Warnstorfia. The other members of the traditional, widely circumscribed genus Drepanocladus in the broad sense that are most closely related to Sanionia are now placed in Drepanocladus and Pseudocalliergon; the latter two genera lack a hyalodermis, have 1–3 rather than 1–8 distal cells of the axillary hairs, and have generally non-plicate rather than plicate leaves. However, because some small phenotypes of Sanionia may also have nearly to entirely non-plicate leaves, the last character should be used with caution. The structures of the alar regions are different, and the exostome margins are more weakly dentate than in S. uncinata, which is the only Sanionia species with an unspecialized peristome. Features separating Sanionia from Hamatocaulis, Loeskypnum, Sarmentypnum, Scorpidium, or Warnstorfia are pointed out in the discussion of 61. Calliergonaceae.

(Discussion copyrighted by Flora of North America; reprinted with permission.)