The Casamayoran () age is a period of geologic time (50.0âÂÂ48.0 Ma) within the Early Eocene epoch of the Paleogene, used more specifically within the South American land mammal age (SALMA) classification. It follows the Itaboraian and precedes the Mustersan age.
Several astrapotherian mammals are known from this period, such as Antarctodon and Albertogaudrya from Antarctica and Argentina, respectively. Albertogaudrya and Scaglia were the size of a sheep or a small tapir, hence among the larger mammals in South America at this time.
This age is named after the Casamayor Formation of the Golfo San Jorge Basin.