A pygostyle from a non-avian theropod

摘要

In birds, vertebrae at the tail end of the backbone are fused into a structure called a pygostyle. We have found a pygostyle from a non-avian theropod, an ovirap-torosaur from the Upper Cretaceous Nemegt Formation of Bugin Tsav, Mongolia. Although this taxon has similarities to birds, it is likely that the pygostyle evolved independently.