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Abstract
Ceratopsians (horned dinosaurs) represent a highly diverse and abundant radiation of non-avian dinosaurs known primarily from the Cretaceous period (65-145 million years ago). This radiation has been considered to be geographically limited to Asia and western North America, with only controversial remains reported from other continents. Here we describe new ceratopsian cranial material from the Late Cretaceous of Iharkút, Hungary, from a coronosaurian ceratopsian, Ajkaceratops kozmai. Ajkaceratops is most similar to 'bagaceratopsids' such as Bagaceratops and Magnirostris, previously known only from Late Cretaceous east Asia. The new material unambiguously demonstrates that ceratopsians occupied Late Cretaceous Europe and, when considered with the recent discovery of possible leptoceratopsid teeth from Sweden, indicates that the clade may have reached Europe on at least two independent occasions. European Late Cretaceous dinosaur faunas have been characterized as consisting of a mix of endemic 'relictual' taxa and 'Gondwanan' taxa, with typical Asian and North American groups largely absent. Ajkaceratops demonstrates that this prevailing biogeographical hypothesis is overly simplified and requires reassessment. Iharkút was part of the western Tethyan archipelago, a tectonically complex series of island chains between Africa and Europe, and the occurrence of a coronosaurian ceratopsian in this locality may represent an early Late Cretaceous 'island-hopping' dispersal across the Tethys Ocean. [PUBLICATION ABSTRACT]