Testing the neoflightless hypothesis: propatagium reveals flying ancestry of oviraptorosaurs

Abstract

Considerable debate surrounds the numerous avian-like traits in core maniraptorans (oviraptorosaurs, troodontids, and dromaeosaurs), especially in the Chinese Early Cretaceous oviraptorosaur Caudipteryx, which preserves modern avian pennaceous primary remiges attached to the manus, as is the case in modern birds. Was Caudipteryx derived from earth-bound theropod dinosaurs, which is the predominant view among palaeontologists, or was it secondarily flightless, with volant avians or theropods as ancestors (the neoflightless hypothesis), which is another popular, but minority view. The discovery here of an aerodynamic propatagium in several specimens provides new evidence that Caudipteryx (and hence oviraptorosaurs) represent secondarily derived flightless ground dwellers, whether of theropod or avian affinity, and that their presence and radiation during the Cretaceous may have been a factor in the apparent scarcity of many other large flightless birds during that period.