Masdevallia decumana is accepted species in  the family Orchidaceae  subfamily: Epidendroideae, tribe: Epidendreae, subtribe: Pleurothallidinae,  
Genus Masdevallia   subgenus Masdevallia  section: Masdevallia   subsection: Caudatae 
Infraspecific taxa recognized within Masdevallia decumana: infraspecific taxa
This species is found in SE. Ecuador to NE. Peru.