Orthosia is a genus of plants in the family Apocynaceae, first described as a genus in 1844.Candolle, Alphonse Louis Pierre Pyramus de. 1844. Prodromus Systematis Naturalis Regni Vegetabilis 8: 526–527
Species 55 species as of May, 2025 accepted at Kew's Plants of the World:Plants of the World Online
Orthosia angustifolia (Schult.) Liede & Meve - Mexico (Veracruz, Puebla, Chiapas) Orthosia boliviana Liede & Meve - Bolivia Orthosia bonplandiana (Schult.) Liede & Meve - Colombia Orthosia calycina (Schltr.) Liede & Meve - Peru Orthosia cardozoi (Schult.) Liede & Meve - Venezuela Orthosia cassythoides (Suess.) Morillo - Venezuela Orthosia congesta (Vell.) Decne. - Brazil Orthosia conradii (Schult.) Liede & Meve - Mexico (Michoacán) Orthosia cynanchoides W.D. Stevens - Mexico (Chiapas) Orthosia dusenii (Malme) Fontella - Brazil Orthosia eichleri E.Fourn. - Brazil Orthosia ellemanniae (Morillo) Liede & Meve - S. Ecuador to Peru Orthosia extra-axillaris W.D. Stevens - Costa Rica Orthosia florida (Vell.) Liede & Meve - N. Venezuela, E. & S. Brazil and NE. Argentina Orthosia glaberrima (Woodson) W.D. Stevens - Panama, Costa Rica Orthosia goyderiana Liede & Meve - Bolivia Orthosia guilleminiana (Decne.) Liede & Meve - Brazil Orthosia henriqueana (Silveira) Liede & Meve - Brazil (Minas Gerais) Orthosia itatiaiensis Malme - Brail (Rio de Janeiro) Orthosia jaliscoensis Liede & Meve - Mexico (Colima, Jalisco) Orthosia leivae Liede & Meve - Ecuador to Peru Orthosia leptocarpa (Rusby) Liede & Meve - NE. Colombia to Venezuela Orthosia loandensis Fontella & Valente - Paraná Orthosia meridensis (Morillo) Liede & Meve - NW. Venezuela Orthosia mexicana (S.Watson) Liede & Meve - Mexico Orthosia micrantha Liede & Meve - Venezuela Orthosia misera (L.O.Williams) W.D.Stevens -- Mexico (Chiapas) to Honduras Orthosia myriantha (Schltr.) Liede & Meve - Peru (Huanuco) to Bolivia Orthosia nicaraguensis Liede & Meve - Nicaragua Orthosia nubicola (Morillo) Liede & Meve - Venezuela Orthosia pallida (Rusby) Liede & Meve - NE. Colombia to NW. Venezuela Orthosia paranaensis Liede & Meve - Brazil (Paraná) Orthosia parviflora (E. Fourn.) Liede & Meve - Rio de Janeiro Orthosia pearcei (Rusby) Liede & Meve - Bolivia Orthosia peruviana (Schltr.) Liede & Meve - Peru (Junín, Pasco) Orthosia pietrangelii (Schltr.) Liede & Meve - Venezuela (Téchira) Orthosia pubescens (Greenm.) Liede & Meve - Central Mexico Orthosia ramosa W.D. Stevens - Honduras Orthosia rariflora (Schltr.) Liede & Meve - Peru (Puno) to W. Bolivia Orthosia retinaculata (Schltr.) Liede & Meve - Bolivia to NW. Argentina Orthosia rubens (L.O. Williams) W.D. Stevens - Guatemala Orthosia scoparia (Nutt.) Liede & Meve - Florida, Georgia, South CarolinaBiota of North America Program 2013 county distribution map, Cynanchum scoparium Orthosia selloana (E. Fourn.) Liede & Meve - Brazil Orthosia sepium (Decne.) Liede & Meve - Mexico (E. Oaxaca) Orthosia smaragdina W.D. Stevens - Guatemala Orthosia stannardii (Morillo) Liede & Meve - Venezuela (Amazonas) Orthosia stenophylla Schltr - Central & S. Colombia Orthosia stipitata W.D. Stevens - Mexico (Chiapas) Orthosia subulata (Vell.) Liede & Meve -SE. & S. Brazil to Argentina (Misiones) Orthosia teodormeyeri Liede & Meve - NW Argentina Orthosia tomentosa (E.Fourn.) Malme - SE. & S. Brazil to Argentina (Misiones) Orthosia umbrosa Decne. - Rio de Janeiro Orthosia urceolata E.Fourn. - Brazil Orthosia virgata (Poir.) E. Fourn. - Argentina Orthosia woodii Meve & Liede - Bolivia Partial list of formerly included taxa:
References