The magnetostràtigraphic study of vallesian sites in the Vallès-Penedès Basin (NE Spain) provides a reliable dating of the earliest appearance of Hipparion at 11.1 Ma. Good agreement with radiometric ages from other sites in Central Europe and Turkey suggests an isochronous dispersal o f this eq uid throughout the Mediterranean region. A possible isochrony at a larger geographical scale (Eurasia and Mesogea) is not ruled out, but must await more reliable ages of other Hipparion first appearance records in Asia and Africa