A taxonomic synopsis and morphological characterization of Myoxanthus (Orchidaceae: Pleurothallidinae) Author Rojas-Alvarado, Gustavo 0000-0002-8918-0823 Jardín Botánico Lankester, Universidad de Costa Rica, Cartago, Apartado 302 - 7050, Costa Rica & gustavo. rojasalvarado @ uc. ac. cr; https: // orcid. org / 0000 - 0002 - 8918 - 0823 gustavo.rojasalvarado@uc.ac.cr Author Blanco, Mario A. 0000-0001-7369-5411 Jardín Botánico Lankester, Universidad de Costa Rica, Cartago, Apartado 302 - 7050, Costa Rica & Centro de Investigación en Biodiversidad y Ecología Tropical, Universidad de Costa Rica, Apdo. 11501 - 2060 San José, Costa Rica & Escuela de Biología, Universidad de Costa Rica, Apdo. 11501 - 2060 San José, Costa Rica & mario. blancocoto @ ucr. ac. cr; https: // orcid. org / 0000 - 0001 - 7369 - 5411 mario.blancocoto@ucr.ac.cr Author Karremans, Adam P. 0000-0001-5987-7710 Jardín Botánico Lankester, Universidad de Costa Rica, Cartago, Apartado 302 - 7050, Costa Rica & Naturalis Biodiversity Center, Endless Forms, Sylviusweg 72, Leiden 2333 BE, The Netherlands & akarremans @ gmail. com; https: // orcid. org / 0000 - 0001 - 5987 - 7710 akarremans@gmail.com text Phytotaxa 2021 2021-06-10 507 3 211 258 http://dx.doi.org/10.11646/phytotaxa.507.3.1 journal article 10.11646/phytotaxa.507.3.1 1179-3163 5425729 35. Myoxanthus panamense Rojas-Alvarado & Karremans , spec. nov. ( Fig. 16 ) TYPE :— PANAMA . Epiphytic along the El Llano-Carti road, 300 m , flowers greenish, cultivated at SEL , 4 Mar 1976 , Luer et al. 1018 ( holotype : MO !, illustration in Luer 1992 t. 34!). Similar to M. scandens but with greenish translucent sepals and petals vs. sepals dark purple and petals stripped with purple, the column sometimes suffused with purple vs. greenish; lip scarcely trilobed with a short bilobed convergent basal callus and a longitudinal pair of low rounded calli near the base extending to nearly the apex vs . lip with a longitudinal pair of conspicuous lamellar keels near the apex. Epiphytic, caespitose, proliferous herbs, up to 40 cm long. Roots fibrous, 1 mm in diameter, branching. Ramicauls cylindrical, flexible, 1 mm in diameter, up to 25 cm long, with up to 12 internodes, the basal ones shorter, producing up to 6 prolific stems at the apex enclosed by tubular, hispidulous sheaths. Sheaths acute, rusty coloured when young, covered by trichomes, imbricate, overlapping up to 5 mm the next internode, the uppermost generally covering the base of the leaves up to 1.5 cm . Leaves narrowly ovate to linear, conduplicate, acute, 3.0–11.0 × 0.2–0.5 cm , subpetiolate, narrowly cuneate basally, minutely tridentate, abscission layer evident. Inflorescence with a reduced peduncle, enclosed during early development by a 3 mm long spathe that frequently disintegrates when old, producing single-flowered coflorescences in succession. Pseudopeduncle 3–4 mm long, whitish with minute trichomes, subtended by a 1.0– 2.5 mm long bract with trichomes to the apex. Floral bract 2.0– 2.5 mm long, covered with minute trichomes. Pedicel 2.0– 2.5 mm long, with a 1.0 mm long filament emerging at the apex. Ovary cylindrical, 1.5‒2.0 mm long, greenish, cellular glandular. Sepals and petals greenish, sometimes with purple spots. Dorsal sepal greenish translucent, ovate, acute 3.0‒4.5 × 1.5 mm , 5-veined. Lateral sepals ovate, acute, 3.0‒3.5 × 1.5–2.0 mm, oblique, 4-veined, connate at the base forming a mentum, sometimes with minute trichomes. Petals wider in their basal half, then gradually contracted into a thickened apex with serrulate margins, 3.0– 3.5 mm long, 2.0 mm wide basally, triveined. Lip oblong, weakly trilobed, 1.5–2.0 × 1.0 mm, suffused with deep purple and yellowish in the middle, hinged to the column foot, apex retuse; lateral lobes erect near the middle, obtusely angled; the base subtruncate with an auricle on each side and a short bilobed convergent callus, the disc with a longitudinal pair of parallel, rounded calli extending from the near the base to near the apex, elevated in the middle. Column semiterete, sometimes suffused with purple, 2 mm long, winged, slightly arched, with an acicular to narrowly acute tooth on each side of the stigma, the clinandrium shortly irregular, dorsally elongate; the anther incumbent, the stigma ventral, column foot 1 mm long. Anther cap 0.5 mm wide, greenish, with purple at the apex. Pollinia two, yellow, obovoid, laterally flattened, 0.3 mm wide, with a pair of small, flat, white caudicles. Fruits capsular, ellipsoid, 7 × 5 mm , dry perianth persistent. Etymology:— Referring to the provenance of this species. Distribution:— Panama . Habitat and ecology:— Found from 50–600 m . It has been collected from Bocas del Toro to the west of Panama Province and recorded flowering all year round . Additional material examined: — PANAMA . Bocas del Toro : hill slope at Boca Chica creek , 5.8 km SE of the community Charco La Pava ,, 550 m , epiphyte on fallen branch, flowers yellow with purple spots, lip heavily spotted purple to dark purple, 21 Oct 2007 , Laube et al. SL 545 ( PMA , Fig. 17 A ) . Colon : Teck Cominco Petaquilla mining concession, forested slopes, epiphytic, perianth translucent white with purple markings, 100 m , 25 Jun 2008 , McPherson 20659 ( PMA ) ; Donoso , Coclé del Norte , Cerca del Río Escribano , área del helicad BL03, bosque húmedo tropical, 46 m , 24 Aug 2012 , Martínez 972 ( PMA ) ; Donoso , Coclé del Norte , Área del helicad C10 , Bosque húmedo tropical, al borde del Río Belencillo , 104 m , 28 Aug 2012 , Martínez 1034 ( PMA ) . Cocle : La Pintada , Palmarazo Río San Juan , Parque Nacional G . D. Omar Torrijos H . Área de Calle Larguita ( Palmarazo ), bosque al norte del área de acampar, Río San Juan , epifita en árbol caído, flor blanca translucida, 180 m , 19 Jul 2013 , Espinosa et al. 6153 ( PMA ) . Panama : La Enedia , region of Cerro Jefe ; epiphyte, flowers yellow-tan, sepal & petals flushed with red-purple, lip dark red-purple, Dressler 3303 ( PMA ) ; Region of Cerro Jefe , epiphyte in tree tops, flowers green flushed with rose-violet, lip dark purple, 15 Oct 1976 , Dressler 3078 ( MO ) ; El Llano-Carti Road , 14 km north of Panamerican Highway , cloud forest; 350-500 m , epiphyte, 22 Jan 1977 , Folsom & Kauke 1407 ( MO ) : Llano-Cartí road, 1 mile past saw mill on dirt road, 300-500 m , sepals, petals, and column yellow with purple, lip, solid red purple, 11 Nov 1979 , Todzia et al. 1023 ( CR ) ; El Llano-Carti Road , 300 m ; epiphyte on tree fall; petals yellowish-clear, Km 12.4, 8 Nov 1984 , de Nevers & Herrera 4230 ( MO ) . Notes:— Plants of this species are almost indistinguishable from the prolific M. sotoanus and M. scandens , with which this species has been confused. However, M. panamense can be distinguished by its greenish translucent sepals vs. purple in M. scandens , brownish in M. sotoanus , petals transluscent greenish vs . purple stripped in M. scandens and translucent yellow in M. sotoanus and column sometimes suffused with purple vs. column yellowish green in the others. The lip is similar to that of M. scandens but differs in having a bilobed short, convergent small basal callus and disc with a longitudinal pair of rounded calli from near the base to near the apex vs. a small callus at the base becoming a pair of conspicuous longitudinal lamellae near the apex where the lamellae becomes frequently irregular. The lip of M. panamense is easily distinguished from that of M. sotoanus because in the former it is purple and weakly trilobed with obtusely angled lateral lobes vs. yellow and conspicuously trilobed with ovate and oblique lateral lobes.