Orthodontium Schwägrichen, 1827.

Orthodontium has been traditionally placed in the family Bryaceae. Recent DNA sequence data suggests that it is best viewed as a member of a separate family. It will probably be identified in the field as a Dicranaceae by an uninitiated worker. The erect and unbranched stems have leaves that appear under the hand-lens to have laminal cells too long and too small to be a Bryaceae. Even with a hand-lens, however, one would be able to see the enlarged alar cells characteristic of Dicranum. Without enlarged alar cells, one might think of such members of the Dicranaceae as Dicranella, but Orthodontium lives on trees and logs, whereas Dicranella lives on soil and on rocks with a bit of soil. In California, Orthodontium is apparently restricted to the perhumid forests near the Pacific Coast, generally among the coastal Sequoia.

Key to Orthodontium

Mosses included in this section are relatively small acrocarps with very narrow leaves but with the cells of the mid-leaf thin-walled. The leaves may be somewhat distorted when dry but they are not truly crispate. The leaf margin is plane to somewhat recurved, and it is nearly entire except at the extreme apex.

Species included are in Orthodontiaceae:
Orthodontium gracile Schwägrichen ex Bruch & W. P. Schimper
Orthodontium pellucens (W. J. Hooker) Bruch & W. P. Schimper in C. Müller Hal.

2008 KEY, P. Wilson

A. Leaves narrowly lanceolate, at mid-leaf the distance from the margin to the costa <3× width of costa, narrowed from base to apex; costa cross-section without stereids (walls only slightly thicker than walls of laminal cells); antheridia placed only a few leaf axils below the perichaetium; exostome teeth evenly tapering from a broad base closely striate with a zig-zag median commissural line .....Orthodontium gracile, common in redwood forest
A. Leaves broader, at mid-leaf the distance from margin to costa >3× width of costa, broadest near the middle; costa cross-section with stereids; antheridia on a short branch near the base of the perichaetial stem; exostome teeth widely separated, bluntly linear and lightly papillose without a median commissural line .....Orthodontium pellucens, fairly rare in California