Bannykus
| Bannykus Temporal range: Early Cretaceous,
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| Holotype displayed in Japan in 2012 | |
Scientific classification 
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| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Superfamily: | †Alvarezsauroidea |
| Genus: | †Bannykus Xu et al., 2018 |
| Type species | |
| †Bannykus wulatensis Xu et al., 2018
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| Synonyms | |
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Bannykus is an alvarezsaur from the Early Cretaceous of the Bayin-Gobi Formation of Inner Mongolia, China. It includes one species, Bannykus wulatensis.
Discovery
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The holotype of Bannykus wulatensis is IVPP V25026, a partially-articulated incomplete skeleton of an 8 year old subadult. The holotype comes from the Bayin-Gobi Formation in Chaoge, Wulatehouqi, Inner Mongolia, China. It was discovered in 2009 and in 2012, its remains were displayed in Japan under the unofficial name "Wulatesaurus". It was given the binomial name Bannykus wulatensis in 2018; its generic name comes from the Mandarin word Ban (Chinese: 半), meaning half, and the Greek word onyx, meaning claw. This refers to the transitional characteristics seen in this theropod. The specific name refers to Wulatehouqi (Wulate Rear Banner), the county that the holotype was found in.[1]
Description
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Bannykus is large for an alvarezsaurian theropod, with an estimated length of 2.77 metres (9.1 ft) and body mass of approximately 24–30 kilograms (53–66 lb) for the immature holotype.[1][2] The forelimb of Bannykus shows significant reduction and modification compared to Haplocheirus, but less shortened and specialized than later alvarezsaurs like Shuvuuia.[1] In 2025, Wang and colleagues identified hard tissue debris and possible soft tissues in the intestinal contents of the holotype (represented by the yellowish conglomerate) based on scanning electron microscopy, which was consistent with further Raman spectroscopy analysis that detected "characteristic peaks indicative of bone-derived material", suggesting that Bannykus probably had a carnivorous diet. The authors concluded that both the forelimb reduction and the dietary shift from carnivory to probably insectivory among alvarezsaurians occurred later in their evolution.[3]
Classification
[edit]Bannykus, along with Xiyunykus, fills a 70-million year gap in alvarezsaur evolution by exhibiting morphologies intermediate between the typical theropod forelimb of Haplocheirus and the highly reduced forelimbs and minute teeth of Late Cretaceous alvarezsaurids.[1]
The cladogram below is the latest and most comprehensive analysis of alvarezsaurian evolution, following Meso et al. (2024).[2]
| Alvarezsauria | |
References
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- ^ a b c d 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. 28 (17): 2853–2860.e3. Bibcode:2018CBio...28E2853X. doi:10.1016/j.cub.2018.07.057. PMID 30146153.
- ^ a b Meso, Jorge Gustavo; Pol, Diego; Chiappe, Luis; Qin, Zichuan; Díaz-Martínez, Ignacio; Gianechini, Federico; Apesteguía, Sebastián; Makovicky, Peter J.; Pittman, Michael. "Body size and evolutionary rate analyses reveal complex evolutionary history of Alvarezsauria". Cladistics. n/a (n/a). doi:10.1111/cla.12600. ISSN 1096-0031. PMC 11811816.
- ^ Wang, S.; Ding, N.; Ma, W.; Yu, W.; Zheng, T.; Choiniere, J.; Xu, X. (2025). "Direct evidence of carnivory in the early-diverging Alvarezsaurian Bannykus". The Innovation Geoscience. doi:10.59717/j.xinn-geo.2025.100143.
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