The Palaeogene tufa deposits at Eocliff are a rich source of micromammals, probably the richest such site in Africa, having yielded thousands of specimens, including complete skulls, mandibles and associated post-cranial elements, with perhaps millions of specimens remaining in the field. Rodents are well-represented but are of relatively low diversity, comprising six common species and a rare one. We here describe an early hystricognath, hystricomorph rodent from the site, based on a complete skull associated with post-cranial elements, and many maxillae, mandibles, isolated teeth and post-cranial bones. This is currently the earliest known member of the superfamily Thryonomyoidea, possible earlier records being based on isolated teeth or fragmentary maxillae and mandibles which do not provide solid evidence for their superfamilial status. The originality of the morphology of the incisors, the simplicity of the molars and other features indicate that this thryonomyoid represents a hitherto unknown family of rodents, herein named Tufamyidae. Keywords: Eocene, Biogeography, Evolution, Taxonomy, Systematics, Rodentia.