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Tsagantegia

Tsagantegia (/ˌsɑːɡɑːnˈteɪɡiə/; meaning Tsagan Teg) is a genus of medium-sized ankylosaurid thyreophoran dinosaur that lived in Asia during the Late Cretaceous period. The genus is monotypic, including only the type species, T. longicranialis. The specimen consists of a very partial individual, comprising the skull and lacking postcranial remains. Since it only preserves the skull, Tsagantegia is mainly characterized by its elongated snout and the flattened facial osteoderms, greatly differing from other ankylosaurs.

Tsagantegia
Temporal range: Late Cretaceous, 92–86 Ma
Diagram of the holotype skull in dorsal and ventral views
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Thyreophora
Clade: †Ankylosauria
Family: †Ankylosauridae
Subfamily: †Ankylosaurinae
Genus: †Tsagantegia
Tumanova, 1993
Type species
†Tsagantegia longicranialis
Tumanova, 1993

Discovery and naming

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The holotype specimen, MPC 700/17, is a virtually complete skull that was recovered from the locality Tsagan-Teg (or "White Mountain") of the Bayan Shireh Formation in the southeastern Gobi Desert, Mongolia. It was formally described in 1993 by the Russian paleontologist Tatyana Alekseyevna Tumanova. The generic name, Tsagantegia, is in reference to Tsagan Teg, the locality of its discovery, and the specific name, longicranialis, is derived from the Latin words longus and crānium, in reference to its elongated skull.[1]

Description

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Skeletal diagram of MPC 700/17

Tsagantegia was a medium to large-sized ankyosaur, with an estimated length of 6 to 7 m (20 to 23 ft)[2][3] and weighing about 1 to 4 t (2,200 to 8,800 lb).[3] The skull measures about 38 cm (380 mm) in length, with a near width of 25 cm (9.8 in), missing the lower jaws. Unlike other Asian ankylosaurs, in Tsagantegia the caputegulae (cranial ornamentation) are not subdivided into a mosaic of polygons but are amorphous and flattened; they show some degree of symmetry. The quadratojugal, squamosal and orbital horns are poorly preserved, in contrast with other ankylosaurs. The snout was long and flat with a pointed rostrum (beak); each maxilla preserves approximately 18 alveoli, no teeth were preserved.[1][2][4] According to Arbour, Tsagantegia differs from Gobisaurus and Shamosaurus based on the more rounded, U-shaped premaxillary beak and the flat ornamentation.[5]

Classification

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Although fragmentary, the phylogenetic position of Tsagantegia can be established. In 2012, Thompson et al. conducted an analysis of almost all known valid ankylosaurs and outgroup taxa at the time. They based their resulting phylogeny on characters representing cranial, post-cranial, and osteodermal anatomy, and details of synapomorphies for each recovered clade. Tsagantegia was found to be closely related to Pinacosaurus and Shamosaurus.[6] In the performed phylogenetic analysis by Arbour and Currie in 2015, below are the results for the analysis:[4]

Ankylosaurinae

Paleoecology

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Tsagantegia compared to the Dinosauria of the Bayan Shireh Formation (Tsagantegia in lime, fourth from left)

Tsagantegia was unearthed from the Tsagan Teg locality, which represents part of the Upper Bayan Shireh.[7] Calcite U–Pb analyses seem to confirm the age of the Bayan Shireh Formation from 92 million to 86 million years ago, Cenomanian-Santonian ages.[8] Based on comparisons between the snouts of Tsagantegia and the contemporary Talarurus, these taxa were divided by niche partitioning. In a palatal view, the rostra Talarurus have a broad-like, rectangular shape, while Tsagantegia have a more shovel-like shaped rostra. These morphological differences indicate that Tsagantegia filled the niche of a browser herbivore, while Talarurus was a grazer.[9]

 
The Bayan Shireh Formation could have looked like the Finke River
 
Fossil localities in Mongolia. Locality of Tsagantegia in Tsagan Teg, at Area D

Caliche-based boundary indicates a semi-arid environment and climate,[10] but also, the presence of fluvial and lacustrine sediments are indicators of large rivers and lakes.[11][12] As interpreted by Hicks et al. 1999, during the times of the Bayan Shireh Formation, large rivers drained the eastern part of the Gobi Desert.[13] Additional to this, fossil fruits remains have been recovered from the Bor Guvé and Khara Khutul localities (Upper and Lower Bayan Shireh, respectively), suggesting the presence of Angiosperm plants.[14]

Tsagantegia shared its habitat with numerous animals from other localities of the formation, compromising dinosaur and non-dinosaur genera; such as the theropods Achillobator,[15] Alectrosaurus,[16] Erlikosaurus,[17] Garudimimus[18] and Segnosaurus;[17] the fellow ankylosaur Talarurus;[19] Marginocephalians: Amtocephale[20] and Graciliceratops;[21] the hadrosauroid Gobihadros,[7] and the large sauropod Erketu.[14] The turtle Lindholmemys,[22] the crocodylomorph Paralligator,[23] unnamed azhdarchids[24] and the shark Hybodus.[12]

See also

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References

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  1. ^ a b Tumanova, T. A. (1993). "O novom pantsirnov dinozavre iz iugo-vostochnoy Gobi" [A new armored dinosaur from Southeastern Gobi]. Paleontologicheskii Zhurnal (in Russian). 27 (2): 92–98.
  2. ^ a b Tumanova, T. A. (2000). "Armoured dinosaurs from the Cretaceous of Mongolia". The Age of Dinosaurs in Russia and Mongolia (PDF). Cambridge University Press. pp. 517–532. Archived (PDF) from the original on 2022-10-01. Retrieved 2024-04-29.
  3. ^ a b Holtz, T. R.; Rey, L. V. (2007). Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages. Random House. Genus List for Holtz 2012 Archived 2012-03-02 at the Wayback Machine Weight Information Archived 2019-12-21 at the Wayback Machine
  4. ^ a b Arbour, V. M.; Currie, P. J. (2015). "Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs". Journal of Systematic Palaeontology. 14 (5): 385–444. doi:10.1080/14772019.2015.1059985. S2CID 214625754.
  5. ^ Arbour, V. M. (2014). Systematics, evolution, and biogeography of the ankylosaurid dinosaurs (PDF) (PhD thesis). p. 265. Archived (PDF) from the original on 2021-04-13. Retrieved 2024-04-29.
  6. ^ Thompson, R. S.; Parish, J. C.; Maidment, S. C. R.; Barrett, P. M. (2012). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. 10 (2): 301–312. Bibcode:2012JSPal..10..301T. doi:10.1080/14772019.2011.569091. ISSN 1477-2019. S2CID 86002282.
  7. ^ a b Khishigjav Tsogtbaatar; David B. Weishampel; David C. Evans; Mahito Watabe (2019). "A new hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous Baynshire Formation of the Gobi Desert (Mongolia)". PLOS ONE. 14 (4): e0208480. Bibcode:2019PLoSO..1408480T. doi:10.1371/journal.pone.0208480. PMC 6469754. PMID 30995236.
  8. ^ Kurumada, Y.; Aoki, S.; Aoki, K.; Kato, D.; Saneyoshi, M.; Tsogtbaatar, K.; Windley, B. F.; Ishigaki, S. (2020). "Calcite U–Pb age of the Cretaceous vertebrate-bearing Bayn Shire Formation in the Eastern Gobi Desert of Mongolia: usefulness of caliche for age determination". Terra Nova. 32 (4): 246–252. Bibcode:2020TeNov..32..246K. doi:10.1111/ter.12456.
  9. ^ Park, J. Y.; Lee, Y. N.; Currie, P. J.; Kobayashi, Y.; Koppelhus, E.; Barsbold, R.; Mateus, O.; Lee, S.; Kim, S. H. (2019). "Additional skulls of Talarurus plicatospineus (Dinosauria: Ankylosauridae) and implications for paleobiogeography and paleoecology of armored dinosaurs". Cretaceous Research. 108: 104340. doi:10.1016/j.cretres.2019.104340. S2CID 212423361.
  10. ^ Martinson, G. G. (1982). "The Upper Cretaceous mollusks of Mongolia". Sovmestnaya Sovetsko– Mongolskaya Paleontolog-icheskaya Ekspeditsia. 17: 5–76.
  11. ^ Samoilov, V. S.; Benjamini, C. (1996). "Geochemical features of dinosaur remains from the Gobi Desert, South Mongolia". PALAIOS. 11 (6): 519–531. Bibcode:1996Palai..11..519S. doi:10.2307/3515188. JSTOR 3515188.
  12. ^ a b Averianov, A.; Sues, H. (2012). "Correlation of Late Cretaceous continental vertebrate assemblages in Middle and Central Asia" (PDF). Journal of Stratigraphy. 36 (2): 462–485. S2CID 54210424. Archived from the original (PDF) on 2019-03-07.
  13. ^ Hicks, J. F.; Brinkman, D. L.; Nichols, D. J.; Watabe, M. (1999). "Paleomagnetic and palynologic analyses of Albian to Santonian strata at Bayn Shireh, Burkhant, and Khuren Dukh, eastern Gobi Desert, Mongolia". Cretaceous Research. 20 (6): 829–850. Bibcode:1999CrRes..20..829H. doi:10.1006/cres.1999.0188. Archived from the original on 2022-05-06. Retrieved 2024-04-29.
  14. ^ a b Ksepka, D. T.; Norell, M. A. (2006). "Erketu ellisoni, a long-necked sauropod from Bor Guvé (Dornogov Aimag, Mongolia)" (PDF). American Museum Novitates (3508): 1–16. doi:10.1206/0003-0082(2006)3508[1:EEALSF]2.0.CO;2. Archived (PDF) from the original on 2021-08-31. Retrieved 2024-04-29.
  15. ^ Perle, A.; Norell, M.A.; Clark, J. (1999). "A new maniraptoran Theropod−Achillobator giganticus (Dromaeosauridae)−from the Upper Cretaceous of Burkhant, Mongolia". Contributions from the Geology and Mineralogy Chair, National Museum of Mongolia (101): 1–105. OCLC 69865262.
  16. ^ Perle, A. (1977). "O pervoy nakhodke Alektrozavra (Tyrannosauridae, Theropoda) iz pozdnego Mela Mongolii" [On the first discovery of Alectrosaurus (Tyrannosauridae, Theropoda) in the Late Cretaceous of Mongolia]. Shinzhlekh Ukhaany Akademi Geologiin Khureelen (in Russian). 3 (3): 104–113.
  17. ^ a b Barsbold, R.; Perle, A. (1980). "Segnosauria, a new suborder of carnivorous dinosaurs" (PDF). Acta Palaeontologica Polonica. 25 (2): 190–192. Archived (PDF) from the original on 2017-03-12. Retrieved 2024-04-29.
  18. ^ Barsbold, R. (1981). "Toothless carnivorous dinosaurs of Mongolia" (PDF). Transactions, Joint Soviet–Mongolian Palaeontological Expedition. 15: 28–39. S2CID 195060070. Archived from the original (PDF) on 2019-12-25.
  19. ^ Maleev, E. A. (1952). "Новый анкилозавр из верхнего мела Монголии" [A new ankylosaur from the Upper Cretaceous of Mongolia] (PDF). Doklady Akademii Nauk SSSR (in Russian). 87 (2): 273–276. Archived (PDF) from the original on 2020-11-05. Retrieved 2024-04-29.
  20. ^ Watabe, M.; Tsogtbaatar, K.; Sullivan, R.M. (2011). "A new pachycephalosaurid from the Baynshire Formation (Cenomanian-late Santonian), Gobi Desert, Mongolia" (PDF). Fossil Record 3. New Mexico Museum of Natural History and Science, Bulletin. 53: 489–497. Archived (PDF) from the original on 2015-09-24. Retrieved 2024-04-29.
  21. ^ Sereno, P.C. (2000). "The fossil record, systematics and evolution of pachycephalosaurs and ceratopsians from Asia". The Age of Dinosaurs in Russia and Mongolia (PDF). Cambridge University Press. pp. 489–491. Archived (PDF) from the original on 2019-12-25. Retrieved 2024-04-29.
  22. ^ Sukhanov, V. B.; Danilov, I. G.; Syromyatnikova, E. V. (2008). "The Description and Phylogenetic Position of a New Nanhsiungchelyid Turtle from the Late Cretaceous of Mongolia". Acta Palaeontologica Polonica. 53 (4): 601–614. doi:10.4202/app.2008.0405.
  23. ^ Turner, A. H. (2015). "A Review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia". PLOS ONE. 10 (2): e0118116. Bibcode:2015PLoSO..1018116T. doi:10.1371/journal.pone.0118116. PMC 4340866. PMID 25714338.
  24. ^ Watabe, M.; Suzuki, D.; Tsogtbaatar, K. (2009). "The first discovery of pterosaurs from the Upper Cretaceous of Mongolia" (PDF). Acta Palaeontologica Polonica. 54 (2): 231–242. doi:10.4202/app.2006.0068. S2CID 53960316. Archived (PDF) from the original on 2021-09-17. Retrieved 2024-04-29.
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