Temporal range: Early Cretaceous, 126–120 Ma
Scaled reconstruction
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Clade: Alvarezsauria
Genus: Xiyunykus
Xu et al., 2018
Type species
Xiyunykus pengi
Xu et al., 2018

Xiyunykus is an alvarezsaur from the Early Cretaceous of the Tugulu Group of China. It includes one species, Xiyunykus pengi.[1]


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.[citation needed]

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.[citation needed]


  1. ^ Xu, Xing; Choiniere, Jonah; Tan, Qingwei; Benson, Roger B.J; Clark, James; Sullivan, Corwin; Zhao, Qi; Han, Fenglu; Ma, Qingyu; He, Yiming; Wang, Shuo; Xing, Hai; Tan, Lin (2018). "Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution". Current Biology. doi:10.1016/j.cub.2018.07.057.