Chilantaisaurus Explained

Chilantaisaurus (" lizard") is a genus of large theropod dinosaur, possibly a neovenatorid or a primitive coelurosaur, from the Late Cretaceous Ulansuhai Formation of China (Turonian age, about 92 million years ago). The type species, C. tashuikouensis, was described by Hu in 1964.

Description

Chilantaisaurus was a large theropod, measuring 11m (36feet) long and weighing 2.5MT4MT.^{[1] [2] [3]} While Brusatte et al. (2010) estimated that Chilantaisaurus might have weighed about 6MT based on femur length similar to that of Tyrannosaurus,^[4] Persons et al. (2020) argued that greater femoral circumference indicates the greater capacity to withstand greater locomotor loads, not greater body mass.^[5]

Classification

Hu considered Chilantaisaurus to be a carnosaur related to Allosaurus,^[6] though some subsequent studies suggested that it may be a spinosauroid, possibly a primitive member of the spinosaurid family (Sereno, 1998; Chure, 2000; Rauhut, 2001) because it had large claws on the forelimbs thought to be unique to that group. Other studies suggested that it could be a member of an alternate offshoot of neotetanuran theropods, with some similarities to allosauroids, spinosauroids, and coelurosaurians.^[7]

A 2009 study noted that it was difficult to rule out the possibility that Chilantaisaurus was the same animal as the carnosaur Shaochilong, which is from the same geological formation. However, they did note an enormous size difference between the two. Further study by Benson, Carrano and Brusatte found that it was not as closely related to Shaochilong as first thought, but that it was a carnosaur (of the family Neovenatoridae), closely related to Allosaurus as Hu had initially thought.^[1] Phylogenetic analysis published by Porfiri et al. in 2018 recovered Chilantaisaurus as a primitive coelurosaurian.^[8] Several species have been described based on very poor remains. The species "Chilantaisaurus" sibiricus (previously informally known as either Allosaurus? sibiricus or Antrodemus? sibiricus) is based on a single distal metatarsal discovered in 1915 in the Turginskaya Svita of the Buryat Autonomous Soviet Socialist Republic, Russia, dating to the Early Cretaceous periods (Berriasian to Hauterivian stages).^{[9] [10] [11]} It is poorly described, so its relationships cannot be accurately determined (Chure, 2000) and its placement as a species of Chilantaisaurus is highly questionable. "Chilantaisaurus" maortuensis was reclassified as Shaochilong maortuensis in 2009.^[12]

An additional species named in 1979, "Chilantaisaurus" zheziangensis, based on bones from the foot and a partial tibia,^[13] is actually a therizinosaur taxon.^{[14] [15]}

The cladogram below follows a 2016 analysis by Sebastián Apesteguía, Nathan D. Smith, Rubén Juarez Valieri, and Peter J. Makovicky based on the dataset of Carrano et al. (2012).^[16]

Notes and References

1. Benson R.B.J. . Carrano M.T. . Brusatte S.L. . 2010 . A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic . Naturwissenschaften . 97 . 1. 71–78 . 10.1007/s00114-009-0614-x . 19826771. 2010NW.....97...71B . 22646156 .
2. Book: Paul, G.S. . 1988 . Predatory Dinosaurs of the World . limited . New York . Simon and Schuster . 314. 9780671619466 .
3. Book: Paul, Gregory S.. The Princeton Field Guide to Dinosaurs. 2016. Princeton University Press. 978-1-78684-190-2. 985402380. 104.
4. Brusatte, S.L. . Chure, D.J. . Benson, R.B.J. . Xu, X. . The osteology of Shaochilong maortuensis, a carcharodontosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Asia . Zootaxa . 2334 . 1–46 . 2010 . 10.11646/zootaxa.2334.1.1 .
5. Persons . S. W. . Currie . P. J. . Erickson . G. M. . An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex . The Anatomical Record . 303 . 4 . 656–672 . 10.1002/ar.24118 . 30897281 . 1932-8486. 2020 . free .
6. Hu. S.-Y.. 1964. Carnosaurian remains from Alashan, Inner Mongolia. Vertebrata PalAsiatica. 8. 1. 42–63. zh, en.
7. Benson . R.B. . Xu, X. . 2008 . The anatomy and systematic position of the theropod dinosaur Chilantaisaurus tashuikouensis Hu, 1964 from the Early Cretaceous of Alanshan, People's Republic of China . Geological Magazine . 10.1017/S0016756808005475 . published online . 6 . 778–789 . 2008GeoM..145..778B . 53356119 .
8. Juan D. Porfiri . Rubén D. Juárez Valieri . Domenica D.D. Santos . Matthew C. Lamanna . 2018 . A new megaraptoran theropod dinosaur from the Upper Cretaceous Bajo de la Carpa Formation of northwestern Patagonia . Cretaceous Research . 89 . 302–319. 10.1016/j.cretres.2018.03.014 . 134117648 .
9. Riabinin, 1915. Zamtka o dinozavry ise Zabaykalya [A note on a dinosaur from the trans-Baikal region]. Trudy Geologichyeskago Muszeyah Imeni Petra Velikago Imperatorskoy Academiy Nauk. 8(5), 133-140.
10. Weishampel, David B; et al. (2004). "Dinosaur distribution (Early Cretaceous, Asia)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 563-570. .
11. Web site: Coelurosauria. theropoddatabase.com.
12. Brusatte, S., Benson, R., Chure, D., Xu, X., Sullivan, C., and Hone, D. (2009). "The first definitive carcharodontosaurid (Dinosauria: Theropoda) from Asia and the delayed ascent of tyrannosaurids." Naturwissenschaften,
13. Book: Dong. Z.. 1979. Mesozoic and Cenozoic Redbeds in Southern China. Cretaceous dinosaur fossils in southern China. Institute of Vertebrate Paleontology and Paleoanthropology. Nanjing Institute of Paleontology. Science Press. Beijing. 342–350. zh. Translated paper
14. L. E.. Zanno. 53405097. 2010. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8. 4. 503–543. 10.1080/14772019.2010.488045.
15. Qian. M.-P.. Zhang. Z.-Y.. Jiang. Y.. Jiang. Y.-G.. Zhang. Y.-J.. Chen. R.. Xing. G.-F.. 2012. 浙江白垩纪镰刀龙类恐龙. Cretaceous therizinosaurs in Zhejiang of eastern China. Journal of Geology. 36. 4. 337−348. chinese.
16. Sebastián Apesteguía . Nathan D. Smith . Rubén Juárez Valieri . Peter J. Makovicky . 2016 . An Unusual New Theropod with a Didactyl Manus from the Upper Cretaceous of Patagonia, Argentina . PLOS ONE . 11 . 7 . e0157793 . 10.1371/journal.pone.0157793 . 27410683 . 4943716. 2016PLoSO..1157793A . free .