Timmiella (De Notaris) Limpricht in Rabenhorst, 1888.

These mosses are plane margined acrocarps dentate near the leaf apices, and high mammillose on the adaxial leaf surface. The leaves are strongly crispate when dry, and in that condition, the pearly white costa seems of radically different coloration from the adjacent leaf.

Key to Timmiella

Timmiella is readily recognized in the field by the combination of plane leaf margins, crispate and opaque leaves (a product of the high mammillose adaxial cells of the bistratose lamina). When moist, Timmiella has an intense green, unlike so many other mosses that seem by comparison mild and translucent.

Species included in this key are in Pottiaceae:
Timmiella anomala (Bruch & W. P. Schimper) Limpricht
Timmiella crassinervis (Hampe) L. Koch

Determination of plants to species may be quite difficult. Plants with sporophytes are easily determined by the straight peristome teeth of Timmiella crassinervis as opposed to the spirally twisted exostome of Timmiella anomala. Unfortunately neither species of Timmiella has sporophytes in any frequency. Even gametangia will often be difficult to find, and so the monoicous sexual condition of Timmiella anomala may be difficult to determine. Without great conviction, we include in the key below the character of leaf base definition – a character mentioned by Crum and Anderson (1981). When sporophytes allow determination, we have found that plants from the humid northwest of the state are usually Timmiella crassinervis, while plants from the drier half of the state are usually Timmiella anomala. Timmiella is almost restricted to seasonally dry mineral soil, usually clayey, often on eroded banks.

A. Leaf bases markedly broader than limb with the contraction to that limb rather abrupt; peristome and exothecial cells of operculum not twisted; plant dioicous .....Timmiella crassinervis
A. Leaf bases hardly broader than limb with no definition of shoulders at base-limb junction; peristome and exothecial cells of operculum twisted about one full spiral; plant monoicous .....Timmiella anomala