Xiyunykus

Xiyunykus (meaning "western claw"; "xiyu" is Mandarin for "west" and refers to Western China where it was found^[1]) is an alvarezsaur from the Early Cretaceous of the Tugulu Group of China. It includes one species, Xiyunykus pengi.^[1]

Xiyunykus Temporal range: Early Cretaceous, 126–120 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scaled reconstruction
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Dinosauria
Clade:	Saurischia
Clade:	Theropoda
Superfamily:	†Alvarezsauroidea
Genus:	†Xiyunykus Xu et al., 2018
Type species
†Xiyunykus pengi Xu et al., 2018

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.^{[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.^[1]