Upper Shishugou crocodyliform
| Upper Shishugou crocodyliform Temporal range: Oxfordian,
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The Upper Shishugou crocodyliform is an as of yet unnamed crocodyliform discovered in the Upper Shishugou Formation in China. It was the first crocodyliform discovered in the entire Shishugou Formation. The crocodyliform specimen has not been studied yet and the exact genus it pertains to remains unknown,[1] although it may have been similar to or synonymous with the contemporaneous Junggarsuchus or Nominosuchus.
History
It is known from a single fully articulated skeleton, found on the same slab that also preserved the holotype of the noasaurid Limusaurus inextricabilis and an associated specimen of L. inextricabilis, which were found in 2001 by a Chinese-American team of paleontologists examining the Wucaiwan locality in the Shishugou Formation, in the northeastern Junggar Basin of Xinjiang, China, discovered three bone beds (numbered TBB 2001; found by T. Yu and J. Mo). The bone beds were dominated by the remains of small theropod dinosaurs, representing at least three genera, with most belonging to a small ceratosaur, with Limusaurus being the first member of this group found in Asia. Stacked skeletons from these bone beds were removed from the field in blocks jacketed by plaster and encased in crates. A resin cast of block TBB 2001 was made (including the crocodyliform specimen), making it available for study after the specimens had been extracted from the original matrix. The crocodyliform specimen from this block and the associated Limusaurus specimens are mounted in a cast of the block in its semi-prepared state.[2][1]
When Limusaurus was described in 2009 by paleontologist Xu Xing and colleagues, the crocodyliform specimen was briefly mentioned during a short footnote - no genus name was given.[1] It has not been described since.
Paleoenvironment
The specimen was recovered from the Shishugou Formation, a succession of sedimentary rocks that was deposited at the northeastern margin of the Junggar foreland basin and is about 350–400 mm (14–16 in) in thickness. The formation is dated to the Late Jurassic, around 161 to 157 million years ago. The unnamed crocodyliform occurs in the upper part of the formation, which represents a variety of environments, including alluvial fans and alluvial plains, streams, wetlands, and shallow lakes. During the time when The unnamed crocodyliform lived, the environment would have been consistently warm and dry, judging by the abundance of coal and carbon-rich deposits.[2][3][1] The climate was probably highly seasonal due to monsoonal influences, with warm, wet summers and dry winters.[4] The climate enabled the growth of a richly forested environment; the forest would have been dominated by Araucaria trees, with the undergrowth being occupied by Coniopteris tree ferns, Anglopteris and Osmunda ferns, Equisetites horsetails, and Elatocladus shrubs.[5]
The environment of the Shishugou Formation hosted a diverse assemblage of animals. More than 35 species of vertebrates are known from fossils, including at least 14 dinosaur species..[2] Contemporaries of The unnamed crocodyliform in the Wucaiwan locality include the theropods Limusaurus, Haplocheirus, Zuolong, and Guanlong, the latter of which is, like Limusaurus, frequently found in mud deposits;[2] the sauropod Mamenchisaurus; the ornithischians Gongbusaurus and Yinlong; the cynodont Yuanotherium; the mammal Acuodulodon; the crocodyliforms Sunosuchus, Junggarsuchus, Nominosuchus; and the turtles Xinjiangchelys and Annemys.[6][2]
References
- ^ a b c d Xu, X.; Clark, J.M.; Mo, J.; Choiniere, J.; Forster, C.A.; Erickson, G.M.; Hone, D.W.E.; Sullivan, C.; Eberth, D.A.; Nesbitt, S.; Zhao, Q.; Hernandez, R.; Jia, C.-K.; Han, F.-L.; Guo, Y. (2009). "A Jurassic ceratosaur from China helps clarify avian digital homologies" (PDF). Nature. 459 (18): 940–944. Bibcode:2009Natur.459..940X. doi:10.1038/nature08124. PMID 19536256. S2CID 4358448. Archived (PDF) from the original on September 22, 2017. Retrieved July 13, 2019.
- ^ a b c d e Eberth, D.A.; Xing, X.; Clark, J.A. (2010). "Dinosaur death pits from the Jurassic of China". PALAIOS. 25 (2): 112–125. Bibcode:2010Palai..25..112E. doi:10.2110/palo.2009.p09-028r. S2CID 131520314. Archived from the original on December 30, 2016. Retrieved December 30, 2016.
- ^ Eberth, D.A.; Brinkman, D.B.; Chen, P.-J.; Yuan, F.-T.; Wu, S.Z.; Li, G.; Cheng, X.-S. (2001). "Sequence stratigraphy, paleoclimate patterns, and vertebrate fossil preservation in Jurassic–Cretaceous strata of the Junggar Basin, Xinjiang Autonomous Region, People's Republic of China". Canadian Journal of Earth Sciences. 38 (12): 1627–1644. Bibcode:2001CaJES..38.1627E. doi:10.1139/e01-067.
- ^ Tutken, T.; Pfretzschner, H.-U.; Vennemann, T.W.; Sun, G.; Wang, Y.D. (2004). "Paleobiology and skeletochronology of Jurassic dinosaurs: implications from the histology and oxygen isotope compositions of bones". Palaeogeography, Palaeoclimatology, Palaeoecology. 206 (3): 217–238. Bibcode:2004PPP...206..217T. doi:10.1016/j.palaeo.2004.01.005.
- ^ Hinz, J.K.; Smith, I.; Pfretzschner, H.-U.; Wings, O.; Sun, G. (2010). "A high-resolution three-dimensional reconstruction of a fossil forest (Upper Jurassic Shishugou Formation, Junggar Basin, Northwest China)". Palaeobiodiversity and Palaeoenvironments. 90 (3): 215–240. doi:10.1007/s12549-010-0036-y. S2CID 140708013.
- ^ He, Y.-M.; Clark, J.M.; Xu, X. (2013). "A large theropod metatarsal from the upper part of Jurassic Shishugou Formation in Junggar Basin, Xinjiang, China" (PDF). Vertebrata PalAsiatica. 51 (1): 29–42. Archived (PDF) from the original on April 2, 2014. Retrieved December 30, 2016.
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