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Tsagantegia

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

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.

Discovery and naming

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The first, and only, discovery of Tsagantegia fossils occurred in 1983, when the Mesozoic team of the Joint Soviet-Mongolian Paleontological Expedition unearthed an ankylosaur skull from the Tsagan-Teg (or "White Mountain") locality near the town of Dzun-Bayan, Mongolia. This locality is one of many deriving from the Bayan Shireh Formation, an Upper Cretaceous (Cenomanian-Turonian)-aged geologic formation in the eastern Gobi Desert, Mongolia. This ankylosaur skull was then deposited at the Institute of Paleontology and Geology of the Mongolian Academy of Sciences (MPC) under specimen number MPC 700/17. This skull remained unresearched until it was described by Russian paleontologist Tatiana Tumanova in 1993. Tumanova described the skull as belonging to a new genus and species of ankylosaurine ankylosaurid, Tsagantegia longicranialis. The generic name, Tsagantegia, is in reference to the Tsagan-Teg locality where the skull was unearthed, and the specific name, longicranialis, comes from the Latin roots longus "long" and cranium "skull" in reference to its elongated skull. Due to being known solely from MPC 700/17, MPC 700/17 was chosen as the holotype (name-bearing) specimen for Tsagantegia longicranialis.[1] Since its description, no additional remains of Tsagantegia longicranialis have been mentioned in scientific literature.[2][3][4]

Description

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Tsagantegia was a medium to large-sized ankyosaur, with an estimated length of 6 to 7 m (20 to 23 ft)[5][6] and weighing about 1 to 4 t (2,200 to 8,800 lb).[6] 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][5][7] According to Arbour, Tsagantegia differs from Gobisaurus and Shamosaurus based on the more rounded, U-shaped premaxillary beak and the flat ornamentation.[8]

Skeletal diagram of MPC 700/17

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.[9] In the performed phylogenetic analysis by Arbour and Currie in 2015, below are the results for the analysis:[7]

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

Paleoecology

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Fossil localities in Mongolia. Locality of Tsagantegia in Tsagan Teg, at Area D

Tsagantegia was unearthed from the Tsagan Teg locality, which represents part of the Upper Bayan Shireh.[10] 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.[11] 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.[12]

The Bayan Shireh Formation could have looked like the Finke River

Caliche-based boundary indicates a semi-arid environment and climate,[13] but also, the presence of fluvial and lacustrine sediments are indicators of large rivers and lakes.[14][15] 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.[16] 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.[17]

Tsagantegia shared its habitat with numerous animals from other localities of the formation, compromising dinosaur and non-dinosaur genera; such as the theropods Achillobator,[18] Khankhuuluu,[19] Erlikosaurus,[20] Garudimimus[21] and Segnosaurus;[20] the fellow ankylosaur Talarurus;[22] Marginocephalians: Amtocephale[23] and Graciliceratops;[24] the hadrosauroid Gobihadros,[10] and the large sauropod Erketu.[17] The turtle Lindholmemys,[25] the crocodylomorph Paralligator,[26] unnamed azhdarchids[27] and the shark Hybodus.[15]

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. ^ Park, Jin-Young (2022). "Cretaceous ankylosaurs of Mongolia: implications for paleobiogeography, paleoecology, and evolution, with a taxonomic review of Mongolian armored dinosaurs". Seoul National University Graduate School Department of Earth and Environmental Sciences: 170–174.
  3. ^ Romano, Marco (2021-01-01). "Disparity versus diversity in ankylosaurid dinosaurs: explored morphospace indicates two separate evolutive radiations". Rendiconti Online della Società Geologica Italiana. doi:10.3301/ROL.2020.22.
  4. ^ Raven, Thomas (2021). "The taxonomic, phylogenetic, biogeographic and macroevolutionary history of the armoured dinosaurs (Ornithischia: Thyreophora)" (PDF). University of Brighton for the degree of Doctor of Philosophy.
  5. ^ 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.
  6. ^ 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
  7. ^ 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. Bibcode:2016JSPal..14..385A. doi:10.1080/14772019.2015.1059985. S2CID 214625754.
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ 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.
  12. ^ 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. Bibcode:2020CrRes.10804340P. doi:10.1016/j.cretres.2019.104340. S2CID 212423361.
  13. ^ Martinson, G. G. (1982). "The Upper Cretaceous mollusks of Mongolia". Sovmestnaya Sovetsko– Mongolskaya Paleontolog-icheskaya Ekspeditsia. 17: 5–76.
  14. ^ 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.
  15. ^ 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.
  16. ^ 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.
  17. ^ 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.
  18. ^ 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.
  19. ^ Voris, Jared T.; Zelenitsky, Darla K.; Kobayashi, Yoshitsugu; Modesto, Sean P.; Therrien, François; Tsutsumi, Hiroki; Chinzorig, Tsogtbaatar; Tsogtbaatar, Khishigjav (2025-06-11). "A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria". Nature. doi:10.1038/s41586-025-08964-6. ISSN 0028-0836.
  20. ^ 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.
  21. ^ 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.
  22. ^ 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.
  23. ^ 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.
  24. ^ 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.
  25. ^ 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.
  26. ^ 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.
  27. ^ 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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