P. distichaceum (Mitt.) Iwats., J. Hattori Bot. Lab. 63: 449. 1987.
Stereodon distichaceus Mitt., J. Linn. Soc, Bot. Suppl. 1: 105. 1859.
Plagiothecium subfalcatum Aust., Musci Appal. 366. 1870.
Isopterygium distichaceum (Mitt.) Jaeg., Ber. Thatigk. St. Gallischen Naturwiss. Ges. 1876-77: 439. 1878.
I. subfalcatum (Aust.) Jaeg., Ber. Thatigk. St. Gallischen Naturwiss. Ges. 1876-77: 438. 1878.
Plagiothecium elegans var. subfalcatum (Aust.) Rau & Herv., Cat. N. Amer. Musci 43. 1880.
Hypnum subfalcatum (Aust.) Lesq. & James, Man. Mosses N. Amer. 371.1884.
Isopterygiumpoasense Ren. & Card., Bull. Soc. Roy. Bot. Belgique 41(1): 141. 1905.
Taxiphyllum howellianum Crum & Anders., J. Elisha Mitchell Sci. Soc. 74: 38. 1958.
Though easily recognized by distant, squarrose-spreading, complanate, cultriform leaves, the Mexican plants differ somewhat from plants occurring elsewhere in North America. The leaves are smooth rather than undulate, the upper cells are uniformly smooth (rather than having some cells dorsally promlose), and there are no twisted-vermiform brood bodies in upper leaf axils.
The species is easily differentiated from P. elegans (Brid.) Iwats. (common in some parts of North America and perhaps to be expected in Mexico) by its asymmetric, often cultriform leaves. When propagula are present, their location and morphology are distinctly different: Pseudotaxiphyllum distichaceum has twisted-vermiform propagula with 1-5 acute teeth at the apex in leaf axils at or near the stem tips. By contrast, P. elegans has axillary, microphyllous propagula somewhat resembling the parent plants below the stem tips.