Interatheriidae
Interatheriidae is an extinct family of notoungulate mammals from South America. Interatheriids are known from the Late Paleocene or Eocene (Mustersan) to the Late Miocene (Huayquerian). These animals were principally small-sized, occupying a habitat like hares, marmots and vizcachas. The majority were very small, like rodents. Interatheriidae is one of the mammal groups that best represent the fauna from the Santa Cruz Formation. Particularly "Protypotherium" with three species is characteristic of the formation: "P.australe", "P. praerutilum" and "P. attenuatum". Another well-known genus is "Interatherium", particularly well represented by "I. robustum".