Goldman (Smiths. Misc. Coll., 60(22):1, February 28, 1913) named the three-toed sloth from extreme eastern Panamá (Marraganti: 1 specimen, the type) and northwestern Colombia (Atrato River: 2 specimens) as Bradypus ignavus.

He characterized the newly-named species as differing from Bradypus griseus (type locality Cordillera de Chucu, Veragua, Panamá) and Bradypus castaneiceps (type locality, Chontales, Nicaragua) in “nasals shorter, with anterior border concave or emarginate, the emargination deepest at median suture; squamosal arm of zygoma broader, more rounded, less acutely pointed anteriorly; palate less deeply grooved posteriorly; symphysis of mandible less produced anteriorly beyond plane of first molars.” Later, Goldman (Smiths. Misc. Coll., 69(5):57-58, April 24, 1920) arranged Bradypus castaneiceps as a subspecies of B. griseus, reaffirmed the full specific identity of Bradypus ignavus, and identified specimens from Tapalisa, Cituro, and Real de Santa Maria, all in eastern Panamá, as belonging to B. ignavus.