Paedotherium is an extinct, potentially paraphyletic[1] genus of Notoungulate, belonging to the family Hegetotheriidae, composed of small-sized, rodent or lagomorph-like South American ungulates.

[2] The first remains associated today with Paedotherium were first described in 1887 by Florentino Ameghino, and attributed to the related genus Pachyruckhos due to an important number of similarities.

In 1926, Lucas Kraglievich revalidated the genus Paedotherium over remains from the Early Pliocene Monte Hermoso Formation of Argentina.

He also associates other remains from the Chapadmalal Formation to the genus, including an humerus and a tibiofabula (MACN 6125), for which he create the species Paediotherium imperforatum.

In 1937, Cabrera described the two new species P. minor and P. affine, from remains from late Miocene rocks of the Arroyo Chasicó Formation.

In 1972 Zetti described Raulringueletia from fragmentary cranial remains (MLP 62-IV-6-1) from the Huayquerian of the Carro Quemado Formation, as well as the new species P. borrelloi, which he thought was intermediate between P. minor (to which he associated P. affine) and P. typicum.

[2] Finally, in 2015, an article authored by Reguero et al created a new species, P.kakai, with S.Sal.Scar.Paleo.2012-045 as holotype, a mandibular fragment with cheek teeths.

It was named kakai after the Cacán language spoken by the native Diaguitas and Calchaquies in the Salta Province, were the holotype of the new species was found.

[1] Originally named Raulringueletia dolichognathus, this species is only known from its holotype, cranial remains with broken teeth from Huayquerian rocks of the Carro Quemado Formation.

The only diagnostic difference of those remains with existing species of Paedotherium is a greater length of the pterygopalatine fossae, and most authors consider it as synonymous with P.

[2] The extinction of the small size notoungulate occurred during a period of climate change, to which rodents and lagomorphs may have been better adapted.