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 6. Myoxanthus cereus (Ames) Luer ex Rojas-Alvarado & Karremans (2017: 210) . (Fig. 12F) Basionym: Pleurothallis cerea Ames (1923a: 19–20) . TYPE :— COSTA RICA . Cartago : Agua Caliente , Lankester 358 ( holotype : K , photo of type, illustration of type, AMES !). Distribution:— Costa Rica and Panama . Notes:— Pleurothallis cerea has been commonly placed under the synonymy of M. octomeriae or M. congestus . However, Luer noted differences between the two species, and in 1991 annotated a specimen collected by Endrés from Costa Rica as “ M. cereus (Ames) Luer ”, a combination that he never published. When Soto (2008) revised the taxonomy of the Mexican Myoxanthus , he reduced M. octomeriae , with all its synonyms, to the synonymy of the older M. congestus , a name based on material from Mexico . However, he also noted the odd features of P. cerea , especially in leaf size and shape and lip structure. After studying material of Pleurothallis cerea from Costa Rica , Rojas-Alvarado & Karremans (2017) formally recognized it as a species and transferred it to Myoxanthus . This Central American species is easily distinguished from the closely related M. octomerioides ( Mexico ) , M. congestus ( Mexico to Colombia-Venezuela) and M. pulvinatus ( Peru and Brazil ) by its broad, elliptic to ovate petiolate leaves, and oblong, conspicuously adaxially verrucose, frequently apiculate lip vs . narrow elliptic, sessile leaves and lip not apiculate of the other species ( Rojas-Alvarado & Karremans 2017 ). FIGURE 12. Myoxanthus species. A –C. M. affinis . D. M. antennifer . E. M. ceratothallis . F. M. cereus . G. M. chloe . H–I. M. cimex . J–K. M. colothrix . L. M. conceicionensis . Photographs by: L. Grobler (A). L.E. Yupanqui (B). G. Rojas-Alvarado (C, J, K). A. Karremans (F, G). Ecuagenera (D). R. Parsons (E, L). S. Vieira-Uribe (H). H. R. Ellis (I).