Plants 0.2--3.0(--6.0) cm, creeping stolons becoming erect, inclined or horizontal to form simple or pinnately branched leafy stems, often with a basal stipe region; flagelliform branches frequent; dark or yellowish green. Stem cortex of orange-brown, thick-walled cells, central strand not differentiated; paraphyllia absent; pseudoparaphyllia filamentous, uniseriate, hyaline; rhizoids mostly restricted to stolons; axillary hairs 2--3 per axil, of 1--2 short brownish basal cells and 2--4 longer hyaline cells. Leaves on stolons scale-like, 0.2--1.25 mm, short-acute or long-acuminate, usually ecostate; in stipe region appressed, erect or recurved from a clasping base, triangular to ovate-acuminate, costa double or single, shorter in distal stem leaves; in stem region leaves erect to spreading or squarrose, lanceolate, ovate-acuminate or orbicular, 1.3--2.6 mm; margins plane, rarely revolute to apex, entire to serrulate distally; costa single to mid-leaf or percurrent, or short and double; cells at insertion dark yellow, thick-walled, porose and irregular; medial laminal cells sinuose, smooth or prorate, rarely with one or two papillae over the cell lumen, walls often porose; distal laminal cells shorter; alar cells little differentiated or rhombic to quadrate in several rows up margin, rarely oblate in many rows extending up margin in lower third of leaf; branch leaves concave, narrowly ovate-acuminate, smooth or weakly plicate, smaller or similar to distal stem leaves. Specialized asexual propagation frequent, clavate gemmae in clusters in leaf axils, reddish brown, uniseriate, of 4--12 quadrate or rectangular cells, thick-walled and verrucose. Sexual condition dioicous. Perigonia on stem and branches, bud-like, with a few scale-like leaves, uniseriate paraphyses and 5--10 antheridia. Perichaetia on stem and branches, urceolate; perichaetial leaves 8--12, the interior ovate-acuminate, abruptly narrowed to long erect awns; multiseriate paraphyses often present. Seta red-brown, 3.0--12.4 mm. Capsule erect, exserted, red-brown, ovate-cylindrical, narrowed to mouth, smooth; stomates absent; operculum rostrate from low, rounded or conic base, rostrum inclined. Peristome with prostome; exostome reduced, teeth 16, often in 8 irregular pairs, incurved when dry, erect when moist, lanceolate, often irregular, inserted below mouth, mostly smooth; endostome consisting of remnants adhering to back of exostome. Calyptra cucullate, fully or partially covering the capsule, with scattered archegonia and paraphyses or smooth, not plicate. Spores spherical, 20--35µm diameter, granulose, green.
Genera ca. 16, species ca. 200 in Pterobryaceae s.str. (3 genera, 4 species in the flora): tropical and subtropical regions worldwide.
The family is highly diverse, and has frequently been the depository of odd tropical taxa excluded from other families. The description above applies only to taxa in the flora area. Few features unite the family as currently circumscribed, and even these are not present in all taxa: tropical, primarily epiphytic habitats; a frondose habit frequently with a differentiated stipe, although this may only be apparent in juvenile plants; uniseriate filamentous pseudoparaphyllia (B. H. Allen 1987); no stomates; reduced peristomes, often with a prostome, and a highly reduced endostome.
The inclusion of Henicodium in the family is questionable on morphological grounds, since the presence of papillae centrally located over the lumen and a revolute leaf margin is otherwise not known in the family. However molecular studies indicate some affinity between Henicodium and Orthostichopsis (W. R. Buck et al. 2000), although Pterobryon, the type genus, is usually placed distantly from both these exemplars (A. E. Newton et al., in prep.). Henicodium is accepted here pending resolution of the family circumscription.
Allen, B. H. 1987. On distinguishing Pterobryaceae and Meteoriaceae by means of pseudoparaphyllia. Bryol. Times 42: 1-3. Arzeni, C. B. 1954. The Pterobryaceae of the southern United States, Mexico, Central America and the West Indies. Amer. Midl. Naturalist. 52: 1--67. Buck, W. R. 1989. Henicodium replaces Leucodontopsis (Pterobryaceae). Bryologist 92: 534. Buck, W. R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82. Buck, W. R., B. Goffinet and A. J. Shaw. 2000. Testing morphological concepts of orders of pleurocarpous mosses (Bryophyta) using phylogenetic reconstructions based on trnL-trnF and rps4 sequences. Mol. Phylog. Evol. 16: 180-198. Newton, A. E. 1993. Phylogenetic systematics of the tropical moss genus Pireella (Pterobryaceae: Musci). Ph.D. Dissertation, Duke University, Durham, North Carolina.
Version History for Pterobryaceae:
Version 2: June 2001
Version 1: May, 2001