Xiyunykus


Xiyunykus is a genus of alvarezsauroid theropod from the Early Cretaceous-aged Tugulu Group of what is now China. Only one species has been described, Xiyunykus pengi.

Paleoecology

Dinosaurs contemporaneous with Xiyunykus in the Tugulu Group of Xinjiang include the stegosaur Wuerhosaurus, the coeval alvarezsaur Tugulusaurus, the carcharodontosaurid Kelmayisaurus, the dubious maniraptoran Phaedrolosaurus, the problematic coelurosaur Xinjiangovenator, and the ceratopsian Psittacosaurus xinjiangensis.

Evolutionary significance

Xiyunykus, along with Bannykus, fills a 70-million year gap in alvarezsaur evolution by exhibiting cranial and postcranial morphologies intermediate between the typical theropod forelimb of Haplocheirus and the highly reduced forelimbs and minute teeth of Late Cretaceous alvarezsaurids.