Pterogonium Swartz, 1801.

Pterogonium gracile, the only worldwide species of the genus, shares with Antitrichia a large suite of characters. Among the most noteworthy of these features are (1) costate leaves with the costa flattened basally; (2) coronate-papillose terminal cells of many of the leaves; (3) tapering and determinate lateral branching; (4) strongly julaceous main stems and branches; (5) long acicular perichaetia; (6) elongate-cylindrical, exserted capsules. The only distinguishing feature between the genera is the presence of prorate-papillosity on the median cells of Pterogonium. Pterogonium is most easily confused in the field with Antitrichia californica, a plant with similar julaceous and tapering axes. A quick hand-lens assessment will, however, show the recurved leaf apices and narrowly but regularly recurved margins of the Antitrichia. When dry, the plants of Pterogonium have a pattern of curling of the tapered lateral branches that, uniquely among mosses, may resemble the profile of a many-toed bird's foot.
see key to Antitrichia Etc.

Species included:
Pterogonium gracile (Hedwig) J. E. Smith