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Lukousaurus

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Lukousaurus
Temporal range: Early Jurassic, 196.5–189.5 Ma Sinemurian
Type anterior skull and mandibles.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Genus: †Lukousaurus
Young, 1940
Species:
†L. yini
Binomial name
†Lukousaurus yini
Young, 1940

Lukousaurus is an archosauromorph based on most of a small skull's snout, displaying distinctive lachrymal horns, found in the Early Jurassic-age Lower Lufeng Formation, Yunnan, China and was described by Chung Chien Young in 1940.[1] The generic name refers to the Lugou Bridge, lit. “crossroads”, near Beijing, where the Sino-Japanese War started.[1] L. yini is tentatively classified as a theropod dinosaur by some allied to ceratosaurs, by others a coelurosaur. Its skull is rather robust for its size though the teeth were described by the author as typically theropodan. Whatever Lukousaurus was, it was definitely an archosauromorph.[2]

History

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At a locality in the town of Huangchiatien (also called Dahungtien) in Yunnan Province, China during the late 1930s, a partial anterior skull and lower jaws as well as possibly a tooth and humerus found nearby.[3][1] The skull was found in the lower Jurassic strata of the Red Beds of the Lufeng Formation, though at the time of its naming in 1940 by Chung Chien Young the beds were thought to date to the Triassic.[3] Young noted that the skull is very strange, with morphologies similar to those of not just Coelurosaurs, which he thought the taxon was, but also Prosauropods and Carnosaurs.[3] The generic name refers to the Lugou Bridge, lit. “crossroads”, near Beijing, where the Sino-Japanese War started and a symbol of the Chinese resistance against Japanese imperialism.[3][1] The species name honors the former deputy Director of the Geological Survey of China, T. H. Yin, who kept work on the survey continuing despite the Japanese invasion.[1] The holotype specimen is housed within the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, China under specimen number IVPP 23.[3][1] Simmons, 1965 assigned a distal humerus and co-ossified tibia and fibula to Lukousaurus, though there is no overlap between elements.[4][1][3]

Classification

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The classification of Lukousaurus is very uncertain due to the strange characteristics of the type specimen and its referred humerus. Lukousaurus was first described as a Coelurosaur based on its postorbital and the shaped of the orbit compared to Saltopus, Podokesaurus, and Ammosaurus, though none of these taxa are now considered Coelurosaurs.[5][6][7][3] The size and "some characteristics of the skull" were also noted as being similar to Palaeosaurus, though Palaeosaurus is considered dubious.[8] Dong Zhiming in his book on Chinese dinosaurs assigned Lukousaurus to Podokesauridae in 1992, a similar conclusion to Young's original classification with Podokesaurus, though in 1997 Kenneth Carpenter placed it as an indeterminate Theropod.[9][10] In 2008, Mickey Mortimer believed that Lukousaurus was either an abelisaurid ceratosaur or a sphenosuchian, but revised her position in 2011 after placing it as a basal pseudosuchian using a phylogenetic matrix developed by Sterling Nesbitt.[11] Knoll et al., 2012 found Lukousaurus to be similar to suchian archosaurs in the anatomy of the antorbital fenestra[2] and Irmis, 2004 stated that Lukousaurus wasn't a theropod dinosaur or a dinosauromorph in general.[12]

References

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  1. ^ a b c d e f g C.-C. Young. (1940). Preliminary notes on the Lufeng vertebrate fossils. Bulletin of the Geological Society of China 20(3-4):235-239
  2. ^ a b Knoll F., Rohrberg K. (2012). CT scanning, rapid prototyping and re-examination of a partial skull of a basal crocodylomorph from the Late Triassic of Germany. Swiss Journal of Geosciences 105:109–115.
  3. ^ a b c d e f g Young, Chung-Chien (1948). "On Two New Saurischians From Lufeng, Yunnan*: Young:-Two New Saurischians From Lufeng". Bulletin of the Geological Society of China. 28 (1–2): 75–90. doi:10.1111/j.1755-6724.1948.mp281-2007.x.
  4. ^ Simmons D.J. (1965), The non-therapsid reptiles of the Lufeng Basin, Yunnan, China. Field Geol 15; 1-93.
  5. ^ Yates, Adam M. (2010-05-12). "A revision of the problematic sauropodomorph dinosaurs from Manchester, Connecticut and the status of Anchisaurus Marsh: THE TAXONOMIC STATUS OF ANCHISAURUS". Palaeontology. 53 (4): 739–752. doi:10.1111/j.1475-4983.2010.00952.x. S2CID 140535438.
  6. ^ Baron, Matthew G.; Norman, David B.; Barrett, Paul M. (2017). "A new hypothesis of dinosaur relationships and early dinosaur evolution". Nature. 543 (7646): 501–506. Bibcode:2017Natur.543..501B. doi:10.1038/nature21700. ISSN 1476-4687. PMID 28332513. S2CID 205254710.
  7. ^ Carrano, Matthew T.; Sampson, Scott D. (2004-09-27). "A review of coelophysoids (Dinosauria: Theropoda) from the Early Jurassic of Europe, with comments on the late history of the Coelophysoidea". Neues Jahrbuch für Geologie und Paläontologie - Monatshefte. 2004 (9): 537–558. doi:10.1127/njgpm/2004/2004/537.
  8. ^ Galton, Peter (2007). "Notes on the remains of archosaurian reptiles, mostly basal sauropodomorph dinosaurs, from the 1834 fissure fill (Rhaetian, Upper Triassic) at Clifton in Bristol, southwest England". Revue de Paléobiologie. 26 (2): 505–591.
  9. ^ Dong, Z., & Tung, C. M. (1992). Dinosaurian faunas of China. Springer.
  10. ^ K. Carpenter, 1997, "A giant coelophysoid (Ceratosauria) theropod from the Upper Triassic of New Mexico, USA", Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 205 (#2): 189-208
  11. ^ Theropod Database Blog post about Lukousaurus
  12. ^ Irmis, R. B. (2004). First report of Megapnosaurus (Theropoda: Coelophysoidea) from China. PaleoBios, 24(3), 11-18.
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