Molecular and morphological results suggest the inclusion of the Anomaluridae and Pedetidae in Hystricomorpha may be suspect.

The modern definition of Hystricomorpha, also known as Entodacrya or Ctenohystrica, is a taxonomic hypothesis uniting the gundis with the hystricognath rodents.

[6] Hystricomorph rodents appeared in South America in the Eocene,[7] a continent which previously had metatherians, xenarthrans, and meridiungulates as the only resident nonflying mammals[citation needed].

The same type of migration may have occurred with primates,[8] which also appeared in South America in the Eocene when it was an isolated continent, long before the Great American Interchange.

Their results rendered the suborder Sciuravida as defined by McKenna & Bell 1997 to be polyphyletic and invalid.