ABSTRACT Four taxa are added to the fossil history of catfishes based on new identifications and descriptions of material from the Miocene Urumaco Formation in northwestern Venezuela. Three of the fossil catfishes belong to the family Doradidae (thorny catfishes); one, Doras dioneae, represents a new species, the first fossil doradid to be formally named, and the other two, Doraops cf. zuloagai and Rhinodoras cf. thomersoni, are referred to modern taxa endemic to the Maracaibo basin. The fourth fossil catfish belongs to the family Pimelodidae (long-whiskered catfishes) and is assigned to Platysilurus, a modern genus that occurs in the Maracaibo, Orinoco, Amazon, and large rivers of the Guianas. These fossil taxa inhabited the paleo-Amazon-Orinoco, a large ancient river system that drained the South American continent northward prior to the uplift of the Eastern Andes and Coastal Cordilleras and concomitant isolation of the Maracaibo basin in the Late Miocene (ca. 8 Ma). Species novum: Doras dioneae Sabaj ...