Studies of herbarium samples and field surveys in Southern California during the fall of 2008 led to the discovery of several new collections of mosses lacking exostome teeth belonging to Orthotrichum Hedw. subgenus Pulchella (Schimp.) Vitt. Some of them are ascribable to O. anodon F. Lara, Garilleti & Mazimpaka even though they display a set of characters not noticed before, considerably broadening the morphological variability of this species and making necessary an updated description. Other materials, from scattered localities along a wide latitudinal range, correspond to a here described new species, Orthotrichum mazimpakanum Garilleti & F. Lara, differentiated by a set of unambiguous characters, including almost smooth, hyaline endostomial segments and partially bistratose leaves. Both mosses are illustrated with SEM and LM photographs, and their similarities and differences are discussed.