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| Kayrasaurus changliensis Liao, Freimuth, Zanno & Xu, 2026; Beipiaosaurus inexpectus; Jianchangosaurus yixianensis; Lingyuanosaurus sihedangensis Artwork by Kōhei Futaka. x.com/_HETAKA |
Abstract
Therizinosauria is a highly specialized clade of maniraptoran theropods, notable for a suite of unusual traits in late-branching taxa. These paradoxical anatomical features contributed to the complex taxonomic history of the clade, which remained unresolved until the discovery of early branching taxa. Here, we describe a new early branching species, Kayrasaurus changliensis, based on a nearly complete, skeletally immature specimen (IVPP V 18597) recovered from the Lower Cretaceous Yixian Formation of western Liaoning, China. This taxon is notably larger than other penecontemporaneous Jehol therizinosaurians (at least 1.6 times larger than the second-largest taxon, Beipiaosaurus inexpectus) and exhibits a unique combination of features (e.g. extremely small and densely packed teeth, cervical centra markedly longer than dorsal centra, and a dorsally extended ‘lip’ on manual ungual IV). We evaluate the phylogenetic position of K. changliensis using an expanded dataset with increased character and taxon sampling. Our results allow us to revise the diagnosis of B. inexpectus and provide new insights into therizinosaurian evolution, provisionally recovering two subclades within Therizinosauridae that are differentiated by their manual ungual morphology. By integrating morphological traits, body mass estimates, and biomechanical data, we infer the possibility of at least two distinct ecological niches among Jehol therizinosaurians. One ecological group, represented by B. inexpectus and possibly K. changliensis, exhibits features indicative of enhanced bite force and a more robust, less cursorial body plan. In contrast, Jianchangosaurus yixianensis and Lingyuanosaurus sihedangensis display traits associated with greater cursoriality and a reliance on forelimb-based foraging. Kayrasaurus changliensis, together with the results of our phylogenetic analysis, provides new insights into the morphological evolution and ecological adaptations of therizinosaurians in the Jehol Biota. However, further analyses and the discovery of more complete, well-preserved specimens are essential to rigorously test and refine these hypotheses.
Keywords: Early Cretaceous, Liaoning, maniraptoran, morphology, taxonomy
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| four species of therizinosaurids from the Jehol Biota, China: Kayrasaurus changliensis; Beipiaosaurus inexpectus; Jianchangosaurus yixianensis; Lingyuanosaurus sihedangensis Artwork by Kōhei Futaka. x.com/_HETAKA |
Systematic palaeontology
Dinosauria Owen, 1842
Theropoda Marsh, 1881
Coelurosauria sensu Gauthier, 1986
Therizinosauria Russell and Dong, 1993
Kayrasaurus changliensis gen. et sp. nov.
Etymology. Kayra, the god of creation in Turkic Shamanism, is the father of Erlik, the god of death, symbolizing its phylogenetic connection to Erlikosaurus; saurus, Greek for lizard. The specific name changliensis is derived from Changli, a historical place name from the Three Kingdoms period, referring to the provenance of the fossil.
Horizon and locality. Dabangou village, Sihetun Area, near Beipiao City, Liaoning Province, P. R. China; Lower Cretaceous (Barremian–Aptian) Yixian Formation (Chang et al., 2017).
Chun-Chi Liao, William J. Freimuth, Lindsay E. Zanno and Xing Xu. 2026. A New therizinosaur from the Early Cretaceous Jehol Biota and ecomorphological patterns among early therizinosaurians. Journal of Systematic Palaeontology. 24(2); 2710287. DOI: doi.org/10.1080/14772019.2026.2710287 [10 Sep 2026]
