Proplatyarthrus

Proplatyarthrus is an extinct genus of ground sloths of the family Megalonychidae, endemic to Chubut Province, Argentina in South America.
Taxonomy.
"Proplatyarthrus" was named and a talus bone described by Florentino Ameghino in 1905. It was assigned to Megalonychidae by Carroll in 1988.
Sister genera.
"Acratocnus", "Ahytherium" (syn. "Iporangabradyx, Iporangabradyx collecti"), "Analcimorphus, Choloepus, Diheterocnus, Hyperleptus, Megalocnus, Megalonychops, Megalonychotherium, Megalonyx" (syn. "Morotherium"), "Meizonyx, Mesocnus, Microcnus, Miocnus, Pliometanastes".