The term Hystricomorpha (from Greek ὕστριξ, hystrix = "porcupine" and Greek μορφή, morphē = "form") has had many definitions throughout its history. In the broadest sense, it refers to any rodent (except dipodoids) with a hystricomorphous zygomasseteric system. This includes the Hystricognathi, Ctenodactylidae, Anomaluridae, and Pedetidae. Molecular and morphological results suggest the inclusion of the Anomaluridae and Pedetidae in Hystricomorpha may be suspect. Based on , these two families are treated here as representing a distinct suborder Anomaluromorpha.