T HE FOSSIL RECORD OF Phoberomys pattersoni M ONES 1980 (M AMMALIA , R ODENTIA ) FROM U RUMACO (L ATE M IOCENE , V ENEZUELA ), WITH AN ANALYSIS OF ITS PHYLOGENETIC RELATIONSHIPS

Synopsis An almost complete skeleton of Phoberomys pattersoni is reported from the Urumaco Formation in northwestern Venezuela. Phoberomys attained the largest body size among known rodents and it lived during the Late Miocene and/or Early Pliocene of Argentina, Brazil and Venezuela. Phoberomys pattersoni is probably the second largest species within its genus. The lower molar enamel shows little difference in thickness between the trailing and leading edges in the first and second lophs, whereas in the third loph the trailing edge is much thinner than the leading edge. In the leading edge of the distal loph the enamel consists of two layers, each covering approximately 50% of the entire enamel thickness, one consisting of thick H unter‐Schreger bands inclined 15–20? towards the occlusal surface, the other formed by radial enamel with the prisms inclined towards the occlusal surface. The postcranial skeleton shows a mosaic of unusual features among caviomorphs (e.g. absence of a supratrochlear foramen) an...