Cramaucheniinae is a paraphyletic subfamily of macraucheniids that originated in the

middle Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "d ...

(

Mustersan The Mustersan age is a period of geologic time (48.0–42.0 Ma) within the Eocene epoch of the Paleogene, used more specifically within the South American land mammal age (SALMA) classification. It follows the Casamayoran and precedes the Divisad ...

SALMA). The size range of the group ranged from small, basal forms to larger and more derived forms. During their evolution, the cramaucheniines undergone a trend from evolving from small basal forms such as ''

Polymorphis ''Polymorphis'' is an extinct genus of litopterns belonging to the family Macraucheniidae. It lived during the Middle Eocene of Argentina. Taxonomy The type species of ''Polymorphis'' is ''Polymorphis lechei''. Both the genus and the species ...

'' into larger, more derived taxa such as '' Theosodon''.

References

Macraucheniids Paleogene mammals of South America Neogene mammals of South America Mammal subfamilies Lutetian first appearances Serravallian extinctions Paraphyletic groups {{Paleo-mammal-stub