Rhytidiadelphus (Limpricht) Warnstorf, 1906.

In California, Rhytidiadelphus is one of our more important "feather mosses," so named because of the plumose branching from a somewhat elevated, decumbent or erect, central stem axis. Most of these feather mosses are quite large, and they usually form extensive, nearly pure colonies on soil or on thin soil over rock outcrops. Rhytidiadelphus stands out among the feather mosses as a plant without paraphyllia, and with a strong double costa that ends near mid-leaf.
see key to Hylocomium Etc.

Species included:
Rhytidiadelphus loreus (Hedwig) Warnstorf
Rhytidiadelphus squarrosus (Hedwig) Warnstorf
Rhytidiadelphus subpinnatus (Lindberg) T. Koponen, not known from CA
Rhytidiadelphus triquetrus (Hedwig) Warnstorf

Rhytidiadelphus in California is infrequently encountered and mainly restricted to the northwest part of the state. Rhytidiadelphus squarrosus is, however, beginning to spread as a lawn weed in that area.