Oldfieldthomasiidae is an extinct family of notoungulate mammals known from the Late Paleocene to Late Eocene of South America.[1] The family was classified by George Gaylord Simpson in 1945 and a synonym is Acoelodidae, defined by Florentino Ameghino in 1901.[2]
The family is named after British zoologist Oldfield Thomas.
Fossils of the family Oldfieldthomasiidae have been found in southern South America, in Argentina, Bolivia, Brazil and Chile.[2]