Monographs Details: Fulfordianthus Gradst.
Authority: Gradstein, S. Robbert. 1994. Lejeuneaceae: Ptychantheae, Brachiolejeuneae. Fl. Neotrop. Monogr. 62: 216. (Published by NYBG Press)
Family:Lejeuneaceae
Scientific Name:Fulfordianthus Gradst.
Synonyms:Thysanopsis R.M.Schust., Lejeunea pterobryoides Spruce, Fulfordianthus pterobryoides (Spruce) Gradst.
Description:Genus Description - Plants dendroid, differentiated into a creeping, stoloniform primary stem which gives rise to several erect, leafy secondary stems, the secondary stems 1-10 cm long × 1.5-4 mm wide, regularly spatiated and densely pinnately, sometimes irregularly branched (forked in female parts), dull dark-green with glossy light-green growing points, becoming brownish on age. Branches thecal, Lejeunea-type, flagelliform branches lacking. Stems rigid, 0.2-0.5 mm in diam., differentiated into a dark brown, thickwalled cortex (4-5 cells across) surrounding a colorless, thin-walled medulla, cortical cells as large as or smaller than the medullary cells, epidermal layer consisting of ca. 60-120 rows of cells; ventral merophyte numerous cells wide (more than 10). Leaves widely spreading and plane or loosely deflexed when dry, convex when moist, leaf lobes ovate to oblong, apex with or without a sharp point, margins plane, crenulate to sharply dentate; leaf cells mostly isodiametrical and small, ca. 10-15 µm long, at leaf base narrowly elongated, 20-40 µm long, forming an obscure, short vitta, all cells (also those of stems) evenly thickened, trigones lacking, oil bodies lacking. Lobules small, up to 1/5× leaf length, never reduced, ovate, at apex with a long (5-10 cells), curved tooth. Underleaves obcuneate, 3-4× stem width, apex deeply emarginate, margins toothed, bases subauriculate, line of insertion straight. Asexual reproduction lacking. Dioicous. Androecia in terminal or intercalary spikes on branches, bracts in 3-25 series, somewhat smaller than leaves, lobules strongly swollen and almost as long as lobes, hypostatic; antheridia two per bract. Gynoecia terminating lateral Lejeunea-type branches or innovations, with paired, repeatedly fertile pycnolejeuneoid innovations forming dichasia, bracts in one series, suberect, toothed, deeply divided into a lobe and a long lobule ca. 2/3× lobe length, keel without wing; bracteole as long as bracts, oblong, sharply keeled-folded over its entire length, apex truncate, margins toothed. Perianths large, cylindrical, 2-3 cm long, sharply 3-keeled, keels entire or slightly toothed towards apex, inner surface of perianth mamillose near apex. Sporophyte: seta not articulate; elaters 72 per capsule; otherwise as in the tribe. Vegetative reproduction not observed.

Discussion:The species of Fulfordianthus grow in the understory of virgin rain forest on bark and occasionally on rock.

Fulfordianthus has traditionally been associated with Thysananthus but has recently been segregated from the latter because of its dendroid growth, regularly pinnate branching, the strongly differentiated subepidermis of the stem, the small isodiametric leaf cells with evenly thickened walls, lacking any trace of trigones, the lack of oil bodies, and the pycnolejeuneoid innovations (Gradstein, 1992). Thiers (1985) recorded the occasional presence of lejeuneoid innovations but I have observed pycnolejeuneoid innovations only. The lack of oil bodies is the most striking feature of this genus and is unique among Lejeuneaceae.

The genus closest to Fulfordianthus is Dendrolejeunea (Spruce) Lacout., a monotypic genus which is widely distributed in tropical Asia (Gradstein, 1992). The only neotropical genus which may be confused with Fulfordianthus is Bryopteris, which has the same growth habit. Bryopteris has many different morphological features, however, and is wholly unrelated to Fulfordianthus. Differences are discussed under F. pterobryoides.

The lack of oil bodies and trigones in Fulfordianthus and the dendroid habit are unusual features within the family Lejeuneaceae and make this genus a highly specialized taxon. Morphological specialization is also found in many other endemic hepatic genera of tropical America and is suggestive of a relatively recent, Tertiary (or late Cretaceous) origin of these taxa (Schuster, 1990). Most of the endemic neotropical hepatics are found in the Antilles, the northern Andes and in the Guayana Highland and adjacent Amazonian lowlands. Fulfordianthus constitutes the first example of a highly apomorphic endemic from the Choco.

Schuster (1992) has recently published a very different description of the ramification system in Fulfordianthus (as Thysanopsis nom. inval.). According to this author, the main axis produces several to many Frullania-type (!) branches prior to ending in a gynoecium; Lejeunea-type branches would be restricted to rather undeveloped microphyllous branches. No mention is made of the dendroid growth habit.

Distribution and Ecology: Fulfordianthus is a neotropical genus with two species in Central America and northwestern South America, at elevations ranging from sea level to 1500 m. The genus is largely restricted to the Choco geographical province, an area which includes the very wet Pacific coast of northern South America and adjacent Central America and which is known for his its high level of endemism among vascular plants (Gentry, 1982). A few records of Fulfordianthus come from western Amazonia. The species of Fulfordianthus grow in the understory of virgin rain forest on bark and occasionally on rock. Fulfordianthus has traditionally been associated with Thysananthus but has recently been segregated from the latter because of its dendroid growth, regularly pinnate branching, the strongly differentiated subepidermis of the stem, the small isodiametric leaf cells with evenly thickened walls, lacking any trace of trigones, the lack oil bodies, and the pyscnolejeuneoid innovations (Gradstein, 1992). Theirs (1985) recorded the occasional presence of lejeuneoid innovations but I have observed pycnolejeuneiod innovations only. The lack of oil bodies is the most striking feature of this genus and is unique among Lejeuneaceae. The genus closest to Fulfordianthus is Dendrolejeunea (Spruce) Lacout., a monotypic genus which is widely distributed in tropical Asia (Gradstein, 1992). The only neotropical genus which may be confused with Fulfordianthus is Bryopteris, which has the same growth habit. Bryopteris has many different morphological features, however, and is wholly unrealted to Fulfordianthus. Differences are dicussed under F. pterobryoides.

The lack of oil bodies and trigones in Fulfordianthus and trigones in Fulfordianthus and the dendroid habit are unusual feather within the family Lejeuneaceae and make this genus a hihgly specialized taxon. Morphological specialization is also found in many other endemic hepatic genera of tropical American and is suggestive of a relatively recent, Tertiary (or late Cretaceous) origin of these taxa (Schuster, 1990). Most of the endemic neotropical hepatics are found in the Antilles, the northern Andes and in the Guayan highland and adjacent Amazonian lowlands. Fulfordianthus constitutes the first example of a highly apomorphic endemic from the Choco.

Schuster (1992) has recently published a very different description of the ramification system in Fulfordianthus (as Thysanopsis nom. inval). According to this author, the main axis produces several to many Frullania- type(!) branches prior to ending in a gynoecium; Lejeunea - type branches would be restricted to rather undeveloped microphyllous branches. No mention is made of the dendroid growth habit