Chilantaisaurus

Chilantaisaurus ("Jilantai Salt Lake lizard"[1]) 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.

Chilantaisaurus
Temporal range: Late Cretaceous,
Skeleton reconstruction of Chilantaisaurus tashuikouensis
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Avetheropoda
Genus: †Chilantaisaurus
Hu, 1964
Species:
†C. tashuikouensis
Binomial name
†Chilantaisaurus tashuikouensis
Hu, 1964

Description
Life restoration

Chilantaisaurus was a large theropod, measuring 11 metres (36 ft) long and weighing 2.5–4 metric tons (2.8–4.4 short tons).[2][3][4] While Brusatte et al. (2010) estimated that Chilantaisaurus might have weighed about 6 metric tons (6.6 short tons) based on femur length similar to that of Tyrannosaurus,[5] Persons et al. (2020) argued that greater femoral circumference indicates the greater capacity to withstand greater locomotor loads, not greater body mass.[6]

Classification
Skeletal diagram showing known elements of C. tashuikouensis

Hu considered Chilantaisaurus to be a carnosaur related to Allosaurus,[1] 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.[8] 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.[2] Phylogenetic analysis published by Porfiri et al. in 2018 recovered Chilantaisaurus as a primitive coelurosaurian.[9]

Manual ungual from the holotype, Tianjin Natural History Museum

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).[10][11][12] 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.[8]

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]

Allosauroidea 

Metriacanthosauridae

Allosauria

Allosauridae

Carcharodontosauria

Carcharodontosauridae

Neovenatoridae

Deltadromeus

Gualicho

Neovenator

Chilantaisaurus

Megaraptora

References
  1. Hu, S.-Y. (1964). "Carnosaurian remains from Alashan, Inner Mongolia" (PDF). Vertebrata PalAsiatica (in Chinese and English). 8 (1): 42–63.
  2. 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. Bibcode:2010NW.....97...71B. doi:10.1007/s00114-009-0614-x. PMID 19826771. S2CID 22646156.
  3. Paul, G.S. (1988). Predatory Dinosaurs of the World. New York: Simon and Schuster. p. 314. ISBN 9780671619466.
  4. Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 104. ISBN 978-1-78684-190-2. OCLC 985402380.
  5. Brusatte, S.L.; Chure, D.J.; Benson, R.B.J.; Xu, X. (2010). "The osteology of Shaochilong maortuensis, a carcharodontosaurid (Dinosauria: Theropoda) from the Late Cretaceous of Asia" (PDF). Zootaxa. 2334: 1–46. doi:10.11646/zootaxa.2334.1.1.
  6. Persons, S. W.; Currie, P. J.; Erickson, G. M. (2020). "An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex". The Anatomical Record. 303 (4): 656–672. doi:10.1002/ar.24118. ISSN 1932-8486. PMID 30897281.
  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" (PDF). Geological Magazine. published online (6): 778–789. Bibcode:2008GeoM..145..778B. doi:10.1017/S0016756808005475. S2CID 53356119.
  8. 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, doi:10.1007/s00114-009-0565-2
  9. 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. doi:10.1016/j.cretres.2018.03.014. S2CID 134117648.
  10. 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.
  11. 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. ISBN 0-520-24209-2.
  12. "Coelurosauria". theropoddatabase.com.
  13. Dong, Z. (1979). "Cretaceous dinosaur fossils in southern China". In Institute of Vertebrate Paleontology and Paleoanthropology; Nanjing Institute of Paleontology (eds.). Mesozoic and Cenozoic Redbeds in Southern China (in Chinese). Beijing: Science Press. pp. 342–350. Translated paper
  14. Zanno, L. E. (2010). "A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora)". Journal of Systematic Palaeontology. 8 (4): 503–543. doi:10.1080/14772019.2010.488045. S2CID 53405097.
  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 (in Chinese). 36 (4): 337−348.
  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. Bibcode:2016PLoSO..1157793A. doi:10.1371/journal.pone.0157793. PMC 4943716. PMID 27410683.
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