Grimmiaceae. Genus Codriophorus
1. Leaves lingulate to ovate; apices broadly rounded; margins serrate to entire —
— Leaves oblong-lanceolate to ovate-lanceolate; apices narrowly rounded; margins entire —
2. Costae subpercurrent, ending shortly below leaf apices, unbranched or occasionally shortly branched near tips; upper leaf margins coarsely serrate —
1. C. acicularis
Rather frequent in Kola Peninsula and Karelia, sporadic in the Urals, known from a few localities in NE European Russia and in the Caucasus. It can be recognized by its rather large, stiff plants and ovate leaves with rounded apices and coarsely serrate upper leaf margins.
— Costa 1/2-3/4 leaf length, often forked; upper leaf margins entire or minutely serrulate —
2. C. mollis
Known from a few localities in southern Kuriles (Kunashir Island), southern Kamchatka and Kommander Islands (Bering Island). Its softer plants with leaves that have shorter costae and less strongly serrate margins differentiate it from C. acicularis. In addition, the two species are allopatric in Russia.
3. Costae stout, 100-180 µm wide at base, in transverse sections at mid-leaf with 4-7 ventral guide cells equal in size to the median/dorsal cells; leaf cells pellucid; leaf apices obtuse —
3. C. aquaticus
Sporadic mainly in the Black Sea coastal area of the Caucasus, and known from a single, disjunct locality in the Southern Urals (Bashkortostan). Confusion with C. acicularis is unlikely because the two species have different distributions in Russia (see also differences in key), as well as different leaf shapes (oblong-lanceolate vs. ovate) and upper leaf margins (entire vs. coarsely serrate).
— Costae moderately slender, 80-105 µm wide at base, in transverse sections at mid-leaf with 2 ventral guide cells larger than other costal cells; leaf cells opaque; leaf apices obtuse or with short hyaline tip —
4. C. carinatus
A rare species known from southern Kamchatka, Primorsky Territory and southern Kuriles (Kunashir Island). It can be separated from all other Far Eastern species of Codriophorus and Dilutineuron by the combination of narrow, lanceolate leaves with very short hyaline apicula; stout subpercurrent costae that in transverse sections have enlarged guide cells; and short leaf cells. D. brevisetum differs from it mainly in having leaves with bistratose costae and ± serrate upper margins.