Reappraisal of the giant caviomorph rodent <italic>Phoberomys burmeisteri</italic> (Ameghino, 1886) from the late Miocene of northeastern Argentina, and the phylogeny and diversity of Neoepiblemidae.

<italic>Phoberomys</italic> is a giant caviomorph rodent included in the extinct Neoepiblemidae. It is recorded in the late Miocene-Pliocene of South America (Argentina, Venezuela, Brazil and Peru), and is one of the largest rodents that have ever lived. In this contribution we study specimens of <italic>Phoberomys</italic> from the ‘Mesopotamiense’, late Miocene of Entre Ríos Province (Argentina), including several unpublished specimens and the holotypes of the five nominal species <italic>(Ph. burmeisteri</italic>, <italic>Ph. praecursor</italic>, <italic>Ph. insolita</italic>, <italic>Ph. lozanoi</italic> and <italic>Ph. minima</italic>) previously recognised for this unit. Our study indicates that all Mesopotamian specimens belong to <italic>Phoberomys burmeisteri</italic>, and that the differences among them reveal individual and ontogenetic variation. Our phylogenetic analysis indicates that Neoepiblemidae is monophyletic and includes <italic>Phoberomys</italic>, <italic>Neoepiblema</italic>, and <italic>Perimys</italic>. <italic>Phoberomys</italic> species are recovered as a clade, which is more closely related to <italic>Neoepiblema</italic> than to the Patagonian <italic>Perimys</italic>. In addition, our study shows that <italic>Eusigmomys</italic> is not a Neoepiblemidae, but a Dinomyidae. [ABSTRACT FROM AUTHOR]