1. Primary stems rhizomatous with abundant rhizoids; outer surface of the exostome teeth regularly thickened, more or less papillose; endostome not adhering to the exostome, basal membrane and cilia present............. 2
1. Primary stems with a few rhizoids; outer surface of exostome teeth often irregularly thickened, smooth; endostome variable, often adhering to the exostome, basal membrane and cilia often absent.......................... 5
2. Secondary stems often simple, usually loosely and irregularly branched; costae double, short and weak....
.......................................................................................................................................................... 3. Garovaglia
2. Secondary stems frondose, often complanately branched in upper parts of stems; costae single or forked................................................................................................................................................................................ 3
3. Leaf costae short, single (less than 1/4 the leaf length) or double; capsules cylindrical......... 13. Trachyloma
3. Leaf costae long, single (more than 3/4 the leaf length); capsules ovoid to spherical...................................... 4
4. Pseudoparaphyllia absent; leaves narrowly ovate; median and upper leaf cells unipapillose....................... 6. Osterwaldiella
4. Pseudoparaphyllia present; leaves cordate; leaf cells smooth................................................... 7. Penzigiella
5. Leaf costae absent or short, double........................................................................................................................ 6
5. Leaf costae single.................................................................................................................................................... 9
6. Leaves auriculate at the base; alar and basal cells not differentiated........................................ 5. Meteoriella
6. Leaves without auricles at the base; alar and basal cells differentiated........................................................... 7
7. Leaves gradually becoming shortly acuminate at the apex...................................................... 11. Pterobryopsis
7. Leaves abruptly constricted into a slender apex.................................................................................................... 8
8. Stems not differentiated into frond and stipe; leaves serrulate at the apex; setae 6–8 mm long
................. 2. Eumyurium
8. Stems differentiated into frond and stipe; leaves usually entire or only denticulate near the apex; setae 2–3 mm long......................................................................................................................... 12. Symphysodontella
9. Leaves cordate and auriculate at the base................................................................................. 1. Calyptothecium
9. Leaves not cordate and not auriculate at the base............................................................................................... 10
10. Leaves not or only slightly concave; alar cells not or only slightly differentiated.................................... 11
10. Leaves distinctly to strongly concave; alar cells clearly differentiated...................................................... 12
11. Leaves ovate-lingulate, acute to obtuse at the apex; endostome filiform............................ 4. Hydrocryphaea
11. Leaves ovate-lanceolate, long-acuminate at the apex; endostome reduced, adhering to the exostome...........
.......................................................................................................................................................... 10. Pterobryon
12. Leaves ovate-lanceolate, slenderly long-acuminate at the apex.............................. 12. Symphysodontella
12. Leaves oblong-oval, blunt or shortly apiculate at the apex......................................................................... 13
13. Leaf costae subpercurrent to shortly excurrent; capsules exserted.................................................. 8. Pireella
13. Leaf costae extending to the mid-leaf or somewhat beyond; capsules immersed.................................................. 9. Pseudopterobryum