[Paleontology • 2026] Kayrasaurus changliensi • A New therizinosaur from the Early Cretaceous Jehol Biota and ecomorphological patterns among early therizinosaurians

 

Kayrasaurus changliensis  Liao, Freimuth, Zanno & Xu, 2026;

Beipiaosaurus inexpectus; Jianchangosaurus yixianensis; Lingyuanosaurus sihedangensis

DOI: doi.org/10.1080/14772019.2026.2710287 

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

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]  

x.com/_HETAKA/status/2098404378852102507

[Paleontology • 2022] Paralitherizinosaurus japonicus • New Therizinosaurid Dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for Function and Evolution of Therizinosaur Claws

Paralitherizinosaurus japonicus

Kobayashi, Takasaki, Fiorillo, Chinzorig & Hikida, 2022

DOI: 10.1038/s41598-022-11063-5

Life reconstruction by Masato Hattori. twitter.com/dgdt2425  

Abstract

The record of therizinosaurs is rich in Asian countries such as Mongolia and China. Fragmentary therizinosaur specimens have been reported from the Lower and Upper Cretaceous deposits in Japan. One of these specimens, from the lower Campanian Osoushinai Formation in Nakagawa Town of Hokkaido Prefecture, was previously identified as a maniraptoran theropod dinosaur, possibly therizinosaur, but its taxonomic status remained unresolved. This study re-examines the specimen and provides a more detailed description and attempts to resolve its taxonomic status. Our study demonstrates that it is a new taxon, Paralitherizinosaurus japonicus gen. et sp. nov., because it shows a unique combination of characters in the metacarpal I and unguals. Our phylogenetic analysis places this new taxon within an unresolved clade of Therizinosauridae in the strict consensus tree. The 50% majority-rule consensus tree shows better resolution within Therizinosauridae, showing an unresolved monophyletic clade of Paralitherizinosaurus, Therizinosaurus, Suzhousaurus, and the Bissekty form. Geometric morphometric analysis suggests that Paralitherizinosaurus unguals most closely resemble Therizinosaurus unguals in being slender and has weak flexor tubercles. This study also shows an evolutionary trend in ungual shape, which associates a decrease in mechanical advantage, development of flexor tubercle, and hypothesized output (product of mechanical advantage and development of flexor tubercle) in derived therizinosaurs, supporting the hook-and-pull function of claws to bring vegetation to its mouth. Paralitherizinosaurus is the youngest therizinosaur from Japan and the first recovered from the marine deposits in Asia. This suggests a long temporal existence of therizinosaurs at the eastern edge of the Asian continent and adaptation of therizinosaurs to coastal environments.

Life reconstruction of Paralitherizinosaurus japonicus

 (Courtesy of Masato Hattori).

 

Map of Japan, showing the location of Nakagawa Town and other dinosaur localities (a).  Two other names in red are locations of other therizinosaur materials. This figure was created by using Adobe Photoshop 21.2.0 and Adobe Illustrator 24.2.1 (https://www.adobe.com/).
A photo of the concretion containing materials of Paralitherizinosaurus japonicus gen. et sp. nov. before preparation (b).
Dark parts in the concretion are exposed bones of Paralitherizinosaurus, showing that all elements were preserved in this block. See Murakami et al.1 for stratigraphic column of the Oshoushinai Formation and the horizon of the specimen. Manual unguals and silhouette of Paralitherizinosaurus japonicus, showing recovered skeletal elements in white (c) (Courtesy of Genya Masukawa).
Life reconstruction of Paralitherizinosaurus japonicus (d) (Courtesy of Masato Hattori).

Theropoda Marsh, 1881

Coelurosauria von Huene, 1920

Therizinosauria Russell, 1997

Therizinosauridae Maleev, 1954

Paralitherizinosaurus japonicus gen. et sp. nov.

 

Etymology: “Paralos” means by or near the sea in Greek, “therizo” means reap in Greek, and “sauros” means reptile in Latin. Specific name, “japon” refers to Japan.

Holotype: NMV-52 (NMV, Nakagawa Museum of Natural History, Japan), a partial vertebra and a partial right hand, including metacarpal I, proximal ends of unguals I and II, and nearly complete ungual III (Fig. 1c).

Horizon and locality: The Osoushinai Formation (early Campanian) of the Yezo Group in Nakagawa Town in Hokkaido Prefecture, Japan.

Diagnosis: A therizinosaurid with the following unique characters: dorsoventrally flattened metacarpal I (dorsoventral height less than half of transverse width) with no rotation of the axis of the distal end; presence of proximodorsally projecting dorsal lip in digits I and III; a shallow depression at the proximal portion of ungual III-4, connecting to the collateral groove; the presence of proximally extending ventral process; a weak flexor tubercle expressed as a small ridge.

    

 

Yoshitsugu Kobayashi, Ryuji Takasaki, Anthony R. Fiorillo, Tsogtbaatar Chinzorig and Yoshinori Hikida. 2022. New Therizinosaurid Dinosaur from the marine Osoushinai Formation (Upper Cretaceous, Japan) provides insight for Function and Evolution of Therizinosaur Claws. Scientific Reports. 12: 7207. DOI: 10.1038/s41598-022-11063-5

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