The Pontils fossil site (middle Eocene, Ebro Basin, Spain) includes several vertebrate-bearing levels situated in a sequence recording a continental to marine transition. Although the locality has been known since the 1980s and scarce mammal remains have been already documented, an intensive sampling has not been developed until now. This work presents the first results of the recent field campaigns carried out at this site. Seven levels have yielded significant vertebrate remains, revealing a diverse assemblage which includes chondrichthyans, actinopterygians, amphibians, crocodilians, squamates, metatherians, eulipotyphlans, apatotherians, chiropterans, rodents, artiodactyls, perissodactyls, and primates, besides other non-vertebrate fossils. The Pontils assemblage indicates a mangrove swamp environment with warm and humid conditions and increasing marine influence towards the top of the sequence. Among mammals, primates are particularly diverse, including abundant remains of a minuscule, still undetermined omomyiform, and scarce teeth of Pseudoloris, Necrolemur, and an undetermined anchomomyin. The occurrence of larger benthic foraminifera allows the assignment of Pontils to Shallow Benthic Zone 17 (Bartonian), solving the debate about the age of the locality, previously assigned either to the Bartonian or the Lutetian. These data, together with previous magnetostratigraphic analyses, allow correlation to chrons C18r or C18n.1r, constraining the age of Pontils to between 39.58 and 41 Ma. Therefore, the Pontils site represents a new reference section for the correlation of marine and continental biostratigraphy during the middle Eocene.