(Calliergon megalophyllum)
Plants large or very large, green, brownish, or yellowish. Stems regularly radially pinnate; axillary hair apical cell elongate-rectangular to short-linear. Stem leaves rounded ovate, broadly rounded ovate, or rounded ovate-cordate; costa single, 74- 105 -m wide near base, ending shortly before apex; alar region sharply delimited, oblong or sometimes triangular, from margins 35-60(-65)% distance to costa; medial laminal cells 84-195 - (7-)8-13-m. Sexual condition dioicous. Spores 13-21 -m.