Grimmiaceae. Genus Coscinodon

1. Leaves not plicate, ovate, with comparatively wide acumen; basal laminal cells at leaf margins quadrate to oblate; peristome teeth weakly perforate, covering urn mouth when moist; Russian Far East 1. C. yukonensis

The species is sporadic in Russian Far East, from Kamchatka to Southern Kuril Islands. It is locally abundant, though very rarely producing sporophytes. Grows on cliffs and rock surfaces in a wide range of altitudes, without any preference to substrates rich in heavy metals. C. yukonensis differs from most species of the genus in non-plicate leaves, which are ovate, usually cucullate and unistratose. Its capsules are deeply immersed, urns short, turbinate, and peristome teeth xerocastique. When sterile, its plants resemble Grimmia reflexidens; however, leaves of the latter species are not cicullate at apex; it is often fruiting, having exserted cylindrical capsules.

Leaves deeply longitudinally plicate, with comparatively narrow acumen; basal laminal cells at leaf margins quadrate or elongate rectangular; peristome teeth perforate, covering urn mouth when moist or not; widespread 2
2. Capsule deeply immersed in perichaetial leaves; peristome teeth squarrose when moist; European and Asian Russia 4. C. cribrosus

The species with wide, but disjunct distribution, in Russia known from scattered localities in the Caucasus, Altai Mts. and Transbaikalia. It grows in xeric habitats, often on rocks rich in heavy metals, but sometimes on other types of rocks. It has strongly plicate leaves, with deep plicae often extending to the base of leaf, partally or completely bistratose distal leaf lamina and long or, occasionally, short hair-points, widened at base but not decurrent, finely scabrose. It differs from all other species of the genus in hygrocastique perstome, with teeth moving outwards when the plants are wetted.

Capsule emergent; peristome teeth covering urn mouth when moist; Asian Russia eastwards from Jenisei River 3
3. Leaves plicate distally; capsule short cylindrical, rounded at base; peristome teeth cribrose 2. C. hartzii

The species is rather widespread in permafrost zone in Asian Russia, from Chukotka and Kamchatka in the north-east to Taimyr in the west, being locally common in Suntar Khayata and Chersky Mountain Ranges in Yakutia; its southernmost localities are in Zabaikalsky Territory. Grows on dry and wet cliffs and rock outcrops, in open and shaded places, often with Mielichhoferia mielihhoferiana, which indicates a high content of heavy metals. It differs from C. cribrosus in shorter plicae in leaves, not extending to the leaf base, emergent capsules on longer seta, and xerocastique peristome.

Leaves plicate from apex to base; capsule elongate, gradually tapering at base; peristome teeth moderately perforated, not cribrose 3. C. pseudohartzii

The species was described from the southern coast of Baikal Lake and also presumably recognized in two collections, from Primorsky Territory and eastern North America (both specimens were sterile). In Baikal Lake area it grew on rock outcrops with high content of copper in mixed birch and larch forest, and in Primorsky Territory on cliffs at the sea shore. In gametophyte characters it is very similar to C. cribrosus, having leaves with deep and long plicae, while its sporophytes resemble C. hartzii, capsules being even longer exserted and with xerocastique peristome.