Species description:
Genus name meaning "little twisted" in reference to the cork­screw twisted peristome teeth. Species name referring to the contorted leaves, when dry.

Reproduction:
Sporophytes occasional, maturing in spring to summer, red-brown and with markedly corkscrew twisted red-brown peristome teeth.

Distinguishing characteristics:
The pinwheel-like arrangement of the leaves at the apex of the stem (best viewed when plants are damp), the pale yellow-green leaves that have undulate margins, the remarkably contorted leaves when dry, and the frequent restriction to calcium-rich sites are useful characters. The leaf, when removed shows a clear basal area of elongate cells that form an M-shaped area as it merges with the opaque elongate point of the leaf. This characterizes the genus Tortella.

Habit:
Forming dense turfs of bright yellow-green plants in which the shoot apex is often formed of pinwheel-like radiating leaves. Leaves strongly contorted when dry.

Similar Species:
T. fragilis has rigid leaves in which the tips break off readily; T. inclinata has bluntish leaf apices; T. humilis is a small plant and the leaves lack undulating margins. Oxystegus tenuirostris is superfi­cially similar but lacks the M-shaped area of clear basal cells; these clear cells gradually merge with the opaque cells. Geheebia gigantea usually produces reddish-brown plants in which the leaves are markedly re­curved and lack the hyaline basal area. Leptodontium recurvifolium has markedly toothed recurved leaves and lacks the basal hyaline area. Ulota obtusiuscula is similar in colour and in the contorted leaves when dry but plants are epiphytic and tufted, and the sporophytes are usually present and bear a hairy calyptra. Trichostomum arcticum can resemble Tortella, especially in the pinwheel-like arrangement of the leaves at the shoot apices. In Trichostomum arcticum, however, the leaf base has a hyaline area that grades gradually into the opaque point, rather than forming an M-shaped area.