An aberrant island-dwelling theropod dinosaur from the Late Cretaceous of Romania

Islands are noted for the occurrence of aberrant, endemic, and dwarfed taxa (the island effect). Late Cretaceous vertebrate assemblages of Romania and elsewhere in Europe are classic examples of island faunas in the fossil record, and are characterized by dwarfed herbivorous dinosaurs and other endemic taxa that are noticeably primitive relative to their mainland contemporaries. Fossils of the predators inhabiting the European paleoislands, however, are exceptionally rare and fragmentary. We describe a new dromaeosaurid theropod, based on an articulated skeleton from the Maastrichtian of Romania, which represents the most complete predatory dinosaur from the middle to Late Cretaceous of Europe. This taxon is characterized by a peculiar body plan, most notably extensive fusion in the hand and distal hindlimb, a highly retroverted pelvis with enlarged femoral muscle attachments, and a pair of hyperextensive pedal claws. However, unlike the island-dwelling herbivorous dinosaurs, its closest relatives are contemporary similar-sized Laurasian taxa, indicating faunal connections between Asia and the European islands late into the Cretaceous. This theropod provides support for the aberrant nature of the Late Cretaceous European island-dwelling dinosaurs, but indicates that predators on these islands were not necessarily small, geographically endemic, or primitive.