编辑：徐 星，舒柯文，王 烁
The systematic position of the enigmatic theropod dinosaur yixianosaurus longimanus
XU Xing, Corwin SULLIVAN, WANG Shuo
Abstract Yixianosaurus longimanus is a small theropod from the Lower Cretaceous of western Liaoning Province, China. It was originally suggested to be a derived maniraptoran, but this interpretation was challenged by a recent study that proposed instead that Y. longimanus was a basal maniraptoran. Given that the systematic position of this taxon will affect our understanding of such broad issues as the evolution of the theropod forelimb and plumage, it is important to carefully evaluate both systematic hypotheses and determine which is better supported. Here we review all available morphological features in Y. longimanus that appear informative with regard to its systematic position. We demonstrate that this small theropod is a basal paravian and most likely a basal deinonychosaurian, a result that conforms to the original interpretation of this specimen. The hypothesis that Y. longimanus is a basal paravian is consistent with the probable presence of pennaceous feathers in this taxon, and avoids implying a complicated evolutionary history for the maniraptoran forelimb.
Key words Liaoning, Early Cretaceous, Maniraptora, Paraves, systematics