Otostylis Schlechter (1918b: 38)

Thiago E. C. Meneguzzo, José F. A. Baumgratz & Cássio Van Den Berg, 2015, Taxonomic studies in the Aganisia complex (Orchidaceae, Zygopetalinae), Phytotaxa 238 (1), pp. 1-39 : 22

4. Otostylis Schlechter (1918b: 38) .

Type (designated by Senghas & Gerlach 1993b: 1698): — Aganisia lepida Linden & Rchb. f. in Reichenbach (1869: 15).

Etymology:— From Greek, αυτί, ear and στήλη, column, due to the column with conspicuous stigmatic wings.

Terrestrial herbs with sympodial growth, caespitose. Roots thick, spongy. Flowering pseudobulb inconspicuous, homoblastic, orbicular in transverse section; cataphylls in the base, leafy, non-scarious, articulate. Leaves 2–4 per pseudobulb, petiole conduplicate, distinct from blade, margin hyaline; blade articulate, plicate, linear to lanceolate, base cuneate, apex acute, abaxial face with 3 primary nerves. Inflorescence racemose, rarely doubly racemose, erect, pedunculate, axillary to inner cataphyll, rachis lax, blooming acropetally; bracts adpressed, lanceolate to deltoid; bracteole 1, shorter than the ovary. Flowers resupinate, pedicellate. Sepals free, elliptic, the lateral ones adnate to column foot and oblique. Petals free, elliptic, narrowly elliptic or obovate, rare oblique. Lip free, motile, trilobed, unguiculate, convex; lateral lobes strongly reduced, deltoid; midlobe orbicular or elliptic, base unguiculate, apex rounded, obtuse or truncate, constricted or not in the base portion; centre of lip with a hippocrepiform callus, tuberculate or composed of digiform processes, apex emarginate or tricuspidate. Column semi-clavate, column foot shorter than the column, apex with trapezoid to oblong conspicuous stigmatic wings; anther incumbent, clinandrium not projecting over the anther, margin entire, external face of anther cap bilobed, apex obtuse-denticulate, inner face bilocular; pollinia 4, in 2 pairs, juxtaposed, oblong-ellipsoid, laterally compressed, unequal in size and shape, tegula oblong-elliptic, caudicle amorphous, sticky, viscidium oblong-elliptic; stigma transverse; rostellum trilobed, midlobe narrowly triangular, lateral lobes reduced, margin concave, lateral lobes reduced, not exceeding the stigma; rostellum remnant trilobed, midlobe acute and unequal to the lateral ones, laterals truncate. Capsules fusiform, 6-carinate, surface smooth; seeds not seen.

Distribution and habitat:— The genus has a similar distribution to that of Aganisia : Trinidad, northern and western South America, Amazon and Solimies Basins, Guyana and Guaporé Shields, but not southern Bahia. Otostylis alba is restricted to the area around Mount Roraima in the Guyana-Venezuelan border, in boggy grassy fields on the edge of moist forests, 900–1,200 m. Otostylis brachystalix is widespread and found near streams, frequently associated with boggy and sandy soils with accumulation of organic matter, in grassy vegetation with the palm Mauritia flexuosa Linnaeus (1782: 454) . In Brazil it grows in biome Amazônia in campinarana and buritizal, which are called in Venezuela morichal; in biome Cerrado in vereda, from sea level to 600 m (all in boggy, grassy fields). TDWG code: 81 TRT-OO 82 GUY-OO SUR-OO VEN-OO 83 CLM-OO PER-OO 84 BZC-MT BZN-AM BZN-PA BZN-RO.

Diagnostic characters:— The genus is distinguished by its medium-sized plants (35–75 cm tall) with caespitose, not rhizomatous, inconspicuous pseudobulbs covered by leafy, articulate, and non-scarious cathaphylls, articulate leaves, petiole with hyaline margin, plicate blade, inflorescence longer than the leaves, lax rachis, medium-sized flowers (sepals up to 1.5 cm long), free sepals, lip entire, constricted in medium of proximal portion, base cordate, callus hippocrepiform with tuberculate or digiform processes, and column with conspicuous stigmatic wings.

Nomenclatural note:— Alrich & Higgins (2011) stated that Pupulin et al. (2009b: 515) selected Zygopetalum brachystalix as the type of the genus. However, it cannot be considered an effective typification because it was not made in an explicit way ( McNeill et al. 2012: art. 7.10), and the type designation was only made in a definitive manner by Senghas & Gerlach (1993b).

Key to the species of Otostylis

1 Lip callus composed of digiform processes, apex emarginate; column length ½ of the lip length.......................................... O. alba

- Lip callus composed of tuberculate processes, apex tricuspidate; column length ⅓ of lip length.............................. O. brachystalix