Macromitrium tumidulum Mitten, J. Linn. Soc., Bot. 12: 201. 1869

Plants reddish brown. Branch leaves with distal leaves widest mid leaf or distally, oblong to oblong-lingulate, 1-1.8 mm; margins entire; apex rounded-obtuse, mucronate, not fragile; costa prominent, ending just below or in mucro; distal laminal cells rounded-hexagonal, 6-9 µm. Sexual condition pseudautoicous, dwarf male plants on leaves and tomentum. Seta 3-5 mm. Capsule oblong to oblong-ovate, 1-1.5 mm. Spores anisosporous, 15-22 µm.

Rock, trees, horizontal branches 1-3 m high; low elevations; Fla.; Mexico; West Indies; Central America; South America.

Groutiella tumidula is distinguished by non-rugose leaves with a length-width ratio of less than 5:1, and by erect branches less than 5 mm high. The apex of the leaf is mucronate and never strongly apiculate, and the leaves are broadly longitudinally plicate when moist.