Omeisaurus (meaning "Omei lizard") is a genus of sauropod dinosaur from the Middle Jurassic to Late Jurassic Period (Bathonian-Oxfordian stage) of what is now China. Its name comes from Mount Emei, where it was discovered in the lower Shaximiao Formation of Sichuan Province.
Like most sauropods, Omeisaurus was herbivorous and large. The largest species, O. tianfuensis, measured long, and weighed .
Discovery and species
Initial discovery and O. changshouensis
The initial discovery of
Omeisaurus was in 1936 when Charles Lewis Camp and
Yang Zhongjian collected a partial skeleton from strata of the Shaximiao Formation in
Sichuan,
China.
[Young, C. C. (1939). On a new Sauropoda, with notes on other fragmentary reptiles from Szechuan. Bulletin of the Geological Society of China, 19(3), 279-315.][Dong, Z. (1983). The dinosaurian remains from Sichuan basin, China. Palaeontologia Sinica, new series C, 23, 1-145.] The material was taken to and prepared in what is now the Institute of Vertebrate Paleontology and Paleoanthropology in
Beijing.
The skeleton was named
Omeisaurus junghsiensis in 1939 by Yang Zhongjian, the skeleton consisting of a partial postcranial skeleton that included four cervical (neck) vertebrae.
It was named after the sacred mountain
Mount Emei, which is near where
O. junghsiensis was found, and the species name after the locality.
The skeleton of
O. junghsiensis was lost during WWII.
In 1955, Xuanmin Li and colleagues collected several Sauropod remains from the same strata as
O. junghsiensis in Changshou during construction of a reservoir.
The IVPP sent Youling Su to conduct the excavation in Changshou, the crew finding eleven vertebrae and several appendicular elements (IVPP V930). The specimen was described later in 1958, also by
Yang Zhongjian,
[Young C C, (1958). New sauropods from China. Vert PalAsiat, 2: 1–28] as a new species,
O. changshouensis.
Discoveries at Wujiaba
During the construction of the Wujiaba Dam in
Zigong during the mid-to-late 1970s, crews discovered many large Sauropod remains from strata of the Upper Shaximiao Formation.
The amount of material was vast and was collected by the Chongqing Museum of Natural History over five years, and was prepped and briefly described.
The material consisted of many partial skulls and skeletons, consisting of between thirteen and sixteen individuals and 2 composite skeletons were later mounted in Chongqing and Zigong.
Wujiaba also saw the collection of a fragmentary partial skull of an additional species of
Omeisaurus,
Omeisaurus fuxiensis, that was described by
Dong Zhiming and colleagues in 1983.
Dashanpu Quarry finds
next and most bountiful
Omeisaurus discovery came in the 1980s when many dinosaur remains were found at
Dashanpu Quarry in
Zigong, these remains including a nearly complete skeleton, several skulls, and additional postcrania from several individuals.
[Li, K., & Cai, K. (1988). The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan: Omeisaurus tianfuensis. Sauropod dinosaurs (2). Sichuan Publishing House of Science and Technology.] The best of these skeletons, a nearly complete and semi articulated postcranial skeleton (ZDM T5701), was selected as the holotype and described by He
et al in 1984.
[X. He, K. Li, K. Cai and Y. Gao. (1984). " Omeisaurus tianfuensis—a new species of Omeisaurus from Dashanpu, Zigong, Sichuan". Journal of Chengdu College of Geology 1984 (suppl. 2): 13-32] A nearly complete skull and partial postcranial skeleton (ZDM T5702) was selected as the paratype, and is one of the few known
Omeisaurus specimens with a well preserved skull. The several specimens were described in much detail later in 1988, with a skeleton mounted at the Zigong Dinosaur Museum sometime later.
Interestingly,
O. tianfuensis was discovered to have a tail club on the end of its caudal vertebrae based on a specimen from Dashanpu.
[Dong Zhiming, Peng Guangzhao and Huang Daxi. 1988. "The Discovery of the bony tail club of sauropods". Vertebrata PalAsiatica 27 (3): 219-224] A second new species was named in 1988,
O. luoquanensis, in the osteology of
O. tianfuensis off of a partial postcranial skeleton.
Recent discoveries
Several
Omeisaurus species have been named since the 1980s, with the most complete of them coming in 2001 with
Omeisaurus maoianus from the Shaximiao Formation in
Jingyang County.
[Tang F, Jin X S, Kang X M et al., 2001. Omeisaurus maoianus: a Complete Sauropoda From Jingyan, Sichuan. Beijing: China Ocean Press. 1–128] O. maoianus was collected by Jin Xingshen and Zhang Guojin during the 1990s and the remains consisted of a skull, partial vertebral column, and several additional postcranial elements (ZNM N8510).
was mounted at the Zhejiang Natural History Museum with its holotype skull on display.
[Xing LD, Miyashita T, Zhang JP, Li DQ, Ye Y, Sekiya T, Wang FP, Currie PJ. 2015b. A new sauropod dinosaur from the Late Jurassic of China and the diversity, distribution, and relationships of mamenchisaurids. Journal of Vertebrate Paleontology. 35 (1):e889701.][Xin-Xin Ren; Jian-Dong Huang; Hai-Lu You (2018). "The second mamenchisaurid dinosaur from the Middle Jurassic of Eastern China". ]Historical Biology: An International Journal of Paleobiology. 49' (2): 185-194. doi:10.1080/08912963.2018.1515935. 10 years later in 2011,
Omeisaurus jiaoi was named based on a well preserved and partially articulated postcranial skeleton, also from Zigong and is deposited at the Zigong Dinosaur Museum (ZDM 5050).
[江山, 李飞, 彭光照, & 叶勇. (2011). A new species of Omeisaurus from the Middle Jurassic of Zigong, Sichuan. 古脊椎动物学报, 49(2), 185-194.] The most recently named
Omeisaurus species,
O. puxiani, was discovered in
Yunyang County and is one of the best preserved
Omeisaurus species, with fossils from most of the vertebral column and girdles recovered.
[Tan, C., Xiao, M., Dai, H., Hu, X. F., Li, N., Ma, Q. Y., ... & You, H. L. (2021). A new species of Omeisaurus (Dinosauria: sauropoda) from the Middle Jurassic of Yunyang, Chongqing, China. Historical Biology, 33(9), 1817-1829.] The specimen is deposited under CLGRP V00005 at the
Chongqing Laboratory of Geoheritage Protection and Research.
Classification
It was once classified as a member of the family
Cetiosauridae, which had long been a wastebasket taxon. The species
O. fuxiensis is sometimes confused with
Zigongosaurus, but the two are based on different material despite having the same species name.
Omeisaurus was formerly assigned to Euhelopodidae.
The cladogram from Tan et al., 2020 below shows a possible phylogenetic position:
Paleoecology
Omeisaurus lived in dense forests. Different species of
Omeisaurus sometimes shared habitats with each other (
O. junghsiensis and
O. tianfuensis, for example). In addition to other species of
Omeisaurus,
Shunosaurus and
Datousaurus are also known from the Xiashaximiao Formation, while
Mamenchisaurus is present in the Shangshaximiao Formation.
Yangchuanosaurus is a large theropod from the Shangshaximiao, and it probably preyed on sauropods. The smaller
Xuanhanosaurus was also present. In the Xiashaximiao, another theropod,
Gasosaurus, was also present, as was the herbivorous
stegosaur Huayangosaurus. The latter probably did not compete with sauropods for food.
External links
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Britt, Carpenter et al. (2002). Encyclopedia of Dinosaurs.. Publications international, Ltd., Lincolnwood Illinois..
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The Middle Jurassic dinosaur fauna from Dashanpu, Zigong, Sichuan. Volume 4. Sauropod dinosaurs (2). Omeisaurus tianfuensis. He, X., Li, K. and Cai, Sichuan Publishing House of Science and Technology, Chengdu ; 1-143 (1988).
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The dinosaurian remains from Sichuan Basin, China. Dong, Z., Zhou, S. and Zhang, Y. PALAEONTOLOGIA SINICA SERIES C (No. 23) i-iii; 1-145 (1983).
