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{{Short description|Extinct genus of dinosaurs}}
{{Automatic taxobox
| fossil_range = <br/>{{fossilrange|Sinemurian|Pliensbachian}}
| image = Yunnanosaurus-Tianjin Natural History Museum.jpg
| image_caption = Fossil jaw, [[Tianjin Natural History Museum]]
|
| authority = Young, 1942
| type_species = {{extinct}}'''''Yunnanosaurus huangi'''''
| type_species_authority = Young, 1942
| subdivision_ranks = [[Species|Other species]]
| subdivision = *{{extinct}}''Y. youngi'' <small>Lu ''et al.'', 2007</small>
*{{extinct}}''Y. robustus''? <small>Young, 1951</small>
}}
'''''Yunnanosaurus''''' ({{IPAc-en|j|uː|ˌ|n|æ|n|oʊ|ˈ|s|ɔːr|ə|s}} {{respell|yoo|NAN|oh|SOR|əs}}) is an [[extinct]] [[genus]] of [[sauropodomorph]] [[dinosaur]] that lived approximately 199 to 183 [[million years ago]] in what is now the [[Yunnan Province]], in [[China]], for which it was named. ''Yunnanosaurus'' was a large sized, moderately-built, ground-dwelling, [[quadrupedal]] [[herbivore]], that could also walk [[bipedal]]ly, and ranged in size from 7 meters (23 feet) long and 2 m (6.5 ft) high to 4 m (13 ft) high in the largest species.
==
[[File:Yunnanosaurus skeleton.jpg|thumb|left|Reconstructed skeletons of ''Yunnanosaurus'' and ''[[Sinosaurus]]'', [[Kunming City Museum]]]]
[[Yang Zhongjian]] (also known as C. C. Young) discovered the first ''Yunnanosaurus'' skeletons in the upper Zhangjiawa Member of the [[Lufeng Formation]] of [[Yunnan]], [[People's Republic of China|China]], dating to the [[Sinemurian]] stage of the [[Early Jurassic]]. The fossil find was composed of over twenty incomplete skeletons, including two skulls, it was excavated by [[Tsun Yi Wang]]. These remains were the basis for the species ''Y. huangi'' (the [[type species]]) and ''Y. robustus.''
In 2007, [[Lü Junchang]] and colleagues described another species of ''Yunnanosaurus'', ''Y. youngi'' (named in honor of C. C. Young). In addition to various skeletal differences, at 13 meters (42 ft) long ''Y. youngi'' was significantly larger than ''Y. huangi'' (which reached only 7 meters [23 ft]). The holotype specimen CXMVZA 185 consists of ten [[cervical vertebrae]], fourteen [[dorsal vertebrae]], three fused [[sacral vertebrae]], seventeen [[caudal vertebrae]], both pubic bones, both ischia, and the right ilium. The skull of this species is not known.<ref name="luetal2007">Lu, J., Li, T., Zhong, S., Azuma, Y., Fujita, M., Dong, Z., and Ji, Q. (2007). "New yunnanosaurid dinosaur (Dinosauria, Prosauropoda) from the Middle Jurassic Zhanghe Formation of Yuanmou, Yunnan Province of China." ''Memoir of the Fukui Prefectural Dinosaur Museum'', '''6''': 1-15.</ref>
The type specimen of ''Yunnanosaurus youngi'' was recovered at the Banqing Houshanliangzi locality of the [[Fengjiahe Formation]],<ref name=":1">{{Cite journal |last1=Ren |first1=Xin-Xin |last2=Su |first2=Xing |last3=Wang |first3=Guo-Fu |last4=You |first4=Hai-Lu |date=2021-10-04 |title=Sedimentological evidence suggests an Early Jurassic age for Yunnanosaurus youngi (Dinosauria: Sauropodomorpha) in Yunnan Province of China |url=https://www.tandfonline.com/doi/full/10.1080/08912963.2021.1984445 |journal=Historical Biology |volume=34 |issue=9 |language=en |pages=1827–1833 |doi=10.1080/08912963.2021.1984445 |s2cid=244227159 |issn=0891-2963|url-access=subscription }}</ref> previously thought to be from the Zhanghe Formation, in Yuanmou County of Yunnan Province, China. The holotype specimen CXMVZA 185 was collected in 2000 in terrestrial sediments deposited during the [[Pliensbachian]] [[Stage (stratigraphy)|stage]] of the [[Early Jurassic]] period, approximately 191 to 183 million years ago. This specimen is housed in the collection of the Chuxiong Museum.
In 2013, Sekiya et al. described the discovery of a juvenile individual which was assigned to ''Yunnanosaurus robustus''.<ref group=Note name=Note01/> Specimen ZMNH-M8739 consists of partial cranial material and an almost complete post-cranial skeleton. This individual possesses characteristic dentition that suggests a potentially unique feeding mechanism as evidenced a tooth–tooth wear facet on its mesial maxillary and dentary teeth, and maxillary teeth that have coarse serrations. Comparison of this juvenile specimen with adult specimens of ''Yunnanosaurus huangi'' reveals very distinctive growth changes.<ref name=":0">{{Cite journal |last1=Sekiya |first1=Toru |last2=Jin |first2=Xingsheng |last3=Zheng |first3=Wenjie |last4=Shibata |first4=Masateru |last5=Azuma |first5=Yoichi |date=2014-03-04 |title=A new juvenile specimen of ''Yunnanosaurus robustus'' (Dinosauria: Sauropodomorpha) from Early to Middle Jurassic of Chuxiong Autonomous Prefecture, Yunnan Province, China |journal=Historical Biology |language=en |volume=26 |issue=2 |pages=252–277 |doi=10.1080/08912963.2013.821702 |bibcode=2014HBio...26..252S |s2cid=85132483 |issn=0891-2963}}</ref>
==Description==
[[File:Yunnanosaurus scale.svg|thumb|Size of ''Y. huangi'' (light green) and ''Y. youngi'' (dark green)]]
===Dentition===
There were more than sixty spoon-shaped teeth in the jaws of ''Yunnanosaurus'', and were unique among early sauropodomorphs in that its teeth were self-sharpening because they "[wore] against each other as the animal fed."<ref name="ageofdinosaursyunnanosaurus">"Yunnanosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 47. {{ISBN|0-7853-0443-6}}.</ref> Scientists consider these teeth to be advanced compared to other early sauropodomorphs, as they share features with the sauropods.<ref name="ageofdinosaursyunnanosaurus"/> However, scientists do not consider ''Yunnanosaurus'' to be especially close to the sauropods in phylogeny because the remaining portions of the animal's body are distinctly "prosauropod" in design.<ref name="ageofdinosaursyunnanosaurus"/> This critical difference implies that the similarity in dentition between ''Yunnanosaurus'' and sauropods might be an example of [[convergent evolution]].<ref name="ageofdinosaursyunnanosaurus"/>
==Classification==
{|style="margin-left: 1em;; margin-bottom: 0.5em; width: 388px; border: #99B3FF solid 1px; background-color: #FFFFFF; color: #000000; float: right; "
|
{{Barlabel|size=15|at=4.5|label=|colour=red|style=font-size:80%
|cladogram=
{{clade| style=font-size:90%;line-height:80%
|label1=[[Plateosauria]]
|1={{clade
|label1=[[Plateosauridae]]
|1={{clade
|1=''[[Jaklapallisaurus]]'' |barbegin1=red
|2=''[[Plateosaurus engelhardti]]'' |bar2=red
|3=''[[Plateosaurus gracilis]]'' |bar3=red
|4=''[[Plateosaurus ingens]]'' |bar4=red
|5=''[[Unaysaurus]]'' |bar5=red
}}
|label2=[[Massopoda]]
|2={{clade
|label1=[[Riojasauridae]]
|1={{clade
|1=''[[Eucnemesaurus]]'' |bar1=red
|2=''[[Riojasaurus]]'' |bar2=red
}}
|2={{clade
|label1=[[Massospondylidae]]
|1={{clade
|1=''[[Massospondylus]]'' |bar1=red
|2=''[[Pradhania]]'' |bar2=red
|3={{clade
|1=''[[Coloradisaurus]]'' |bar1=red
|2={{clade
|1=''[[Glacialisaurus]]'' |bar1=red
|2=''[[Lufengosaurus]]'' |bar2=red
}}
}}
}}
|label2=[[Anchisauria]]
|2={{clade
|1=''[[Anchisaurus]]'' |bar1=red
|2=''[[Jingshanosaurus]]'' |bar2=red
|3=''Yunnanosaurus'' |barend3=red
|4={{clade
|1=''[[Melanorosaurus]]''
|2=[[Sauropoda]]
}}
}}
}}
}}
}}
}}
{{center|<small>The red bracket identifies members of the group "Prosauropoda".<br />
Plateosauria [[cladogram]] based on the [[phylogenetics|phylogenetic analysis]], conducted by [[Fernando E. Novas|Novas]] ''et al.'', 2011.<ref name=novas11/></small>}}
}}
|}
The [[type species]], ''Y. huangi'', was named by [[Yang Zhongjian|C. C. Young]] in 1942, who erected the family Yunnanosauridae to contain it, though the family currently comprises only this genus and sometimes ''[[Jingshanosaurus]]''. The specific name honours Huang Chiching ("T.K. Huang"), the director of the National Geological Survey of China.<ref name="young1942">Young, C. C. (1942). "[https://onlinelibrary.wiley.com/doi/10.1111/j.1755-6724.1942.mp221-2005.x ''Yunnanosaurus huangi'' Young (gen. et sp. nov.), a new Prosauropoda from the red beds at Lufeng, Yunnan.]" ''Bulletin of the Geological Society of China'', '''22''' (1-2): 63-104.</ref> Young also named a second species, ''Y. robustus'', in 1951,<ref name="ageofdinosaursyunnanosaurus"/><ref name="young1951">Young, C. C. (1951). "The Lufeng saurischian fauna in China."
''Paleontologica Sinica'', ser. C, '''13''': 1-96.</ref> but this has since been [[inclusion (taxonomy)|included]] in the type species.<ref name="ageofdinosaursyunnanosaurus"/> The confusion in classification arose due to that the earliest specimens of ''Y. huangi'' were of juvenile individuals while the ''Y. robustus'' specimens represented fully grown adults.<ref name="ageofdinosaursyunnanosaurus"/> However, Sekiya ''et al.'' (2013) described a juvenile of ''Y. robustus'' and were able to differentiate it from ''Y. huangi''. ''Yunnanosaurus'' had been assigned to several taxa over the years, including [[Thecodontosauridae]] and [[Plateosauridae]], but a more recent phylogenetic analysis conducted by Novas ''et al.'' (2011) shows that this genus is part of the taxon [[Massopoda]] in a clade with ''[[Anchisaurus]]'' and ''[[Jingshanosaurus]]''.<ref name="novas11">Fernando E. Novas, Martin D. Ezcurra, Sankar Chatterjee and T. S. Kutty (2011). "New dinosaur species from the Upper Triassic Upper Maleri and Lower Dharmaram formations of central India". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 101 (3-4): 333–349. doi:10.1017/S1755691011020093</ref> Apaldetti et al. (2011) also found that ''Yunnanosaurus'' belonged in [[Massopoda]], but found that this genus was more primitive than both ''Jingshanosaurus'' and ''Anchisaurus''.<ref>{{cite journal |year=2011 |title=A New Basal Sauropodomorph (Dinosauria: Saurischia) from Quebrada del Barro Formation (Marayes-El Carrizal Basin), Northwestern Argentina |journal=PLOS ONE |volume=6 |issue=11 |pages=e26964 |doi=10.1371/journal.pone.0026964 |author=Cecilia Apaldetti, Ricardo N. Martinez, Oscar A. Alcober and Diego Pol |editor1-last=Claessens |editor1-first=Leon |pmid=22096511 |pmc=3212523 |bibcode=2011PLoSO...626964A |doi-access=free }}</ref>
===Distinguishing anatomical features===
A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism.
==== ''Y. huangi'' ====
According to Barrett et al. (2007), the skull of ''Y. huangi'' can be distinguished from other sauropodomorphs based on the following characteristics:<ref>{{Cite journal |last1=Barrett |first1=Paul M. |last2=Upchurch |first2=P. |last3=Zhou |first3=X.-D. |last4=Wang |first4=X.-L. |date=June 2007 |title=The skull of ''Yunnanosaurus huangi'' Young, 1942 (Dinosauria: Prosauropoda) from the Lower Lufeng Formation (Lower Jurassic) of Yunnan, China |journal=Zoological Journal of the Linnean Society |volume=150 |issue=2 |pages=319–341 |doi=10.1111/j.1096-3642.2007.00290.x |issn=1096-3642|doi-access=free }}</ref>
* a small external [[naris]]
* a robust expanded nasal process of the [[premaxilla]]
* a downward projection from the rear of the maxillary ascending process
* no nutritive foramina on the lateral surface of [[maxilla]]
* a shallow circular depression on the lateral surface of the ventral lacrimal process
* a midline boss near the front of the frontals
* a prominent midline boss on the [[Parietal bone|parietals]]
* the anterolateral process of the parietal is expanded relative to the width of the posterolateral process
* the maxillary teeth are narrow and do not have denticles
Additionally, Sekiya ''et al.'' (2013) add one more character distinguishing ''Y. huangi'': a hemispherical neural spine in the posterior cervical vertebrae.<ref name=":0" />
==== ''Y. youngi'' ====
According to Lu et al. (2007), ''Y. youngi'' can be distinguished from ''Y. huangi'' based on the following characteristics:<ref name="luetal2007" />
* the sixth cervical vertebra is the longest among the vertebral column
* the neural spines of the posterior cervical vertebrae are short with an expanded distal end, which is wider than its anteroposterior length
* three sacral vertebrae are tightly fused with a stout sacrocostal yoke
* the ventral margin of the postacetabular process of the [[Ilium bone#In dinosaurs|ilium]] is slightly concave
* the [[Ischium#In dinosaurs|ischium]] is longer than the pubis
* the distal end of the [[pubis (bone)#Dinosaurs|pubis]] is round
==== ''Y. robustus'' ====
According to Sekiya et al. (2013), ''Yunnanosaurus robustus'' can be distinguished from other sauropodomorphs based on the following characteristics:<ref name=":0" />
* the absence of the anteroposterior expansion on the medial end of the [[talus bone|astragalus]]
* the shaft of the metatarsal IV is dorsoventrally compressed
==Paleoecology==
The type specimens of ''Yunnanosaurus huangi'' and ''Yunnanosaurus robustus'' were recovered in the Huangchiatien (Dahungtien) locality of the [[Lufeng Formation]] in Yunnan, China. The ''Y. huangi'' [[holotype]] specimen IVPP V20 and the ''Y. robustus'' holotype specimen IVPP V93, were collected by Chung Chien Young in terrestrial sediments from the upper dark/deep red beds of the Zhangjiawa Member of this formation, that are believed to have been deposited during the [[Sinemurian]] [[Stage (stratigraphy)|stage]] of the [[Jurassic]] period, approximately 199 to 190 million years ago.<ref name=LuoWu94>Luo, Z., and X.-C. Wu. 1994. The small tetrapods of the Lower Lufeng Formation, Yunnan, China; pp. 251–270 in N. C. Fraser and H.-D.Sues (eds.), In the Shadow of the Dinosaurs. Cambridge University Press, New York</ref> Several other specimens assigned to ''Y. huangi'' (IVPP V54, IVPP V47, IVPP V61, IVPP V62, IVPP V63, IVPP V96, IVPP V264), and ''Y. robustus'' (IVPP V39, IVPP V94) were also recovered by Young in this locality. These specimens are all housed in the collection of the [[Institute of Vertebrate Paleontology and Paleoanthropology]], in [[Beijing]], China. In the years to come several more specimens assigned to these two species were recovered from Zhangjiawa Member of this formation.
Chung Chien Young had also explored the lower dark/dull purple beds of the Shawan Member of the Lufeng Formation and found more specimens that he later assigned to ''Y. huangi''. Specimen IVPP V32 was collected by Young in 1938 in dark red, argillaceous sandstone that is believed to have been deposited during the [[Hettangian]] [[Stage (stratigraphy)|stage]] of the [[Jurassic]] period, approximately 201 to 199 million years ago.<ref name=LuoWu94/> Specimens IVPP V57, IVPP V60 and IVPP V272 were collected by Young in blue mudstone from the same formation and were also assigned to ''Y. huangi''. These specimens from the Shawan Member are also housed in the collection of the Institute of Vertebrate Paleontology and Paleoanthropology.
''Yunnanosaurus huangi'' and ''Yunnanosaurus robustus'' shared their [[natural environment|paleoenvironment]] with the [[ornithischians]] ''[[Bienosaurus]]'', and ''[[Tatisaurus]]'', the [[sauropodomorphs]] ''[[Gyposaurus]]'', ''[[Lufengosaurus]]'', and ''[[Jingshanosaurus]]'', and the [[theropods]] ''[[Sinosaurus]] triassicus'' and ''[[Eshanosaurus]]''.
==Notes==
{{Reflist|group=Note|refs=
<ref name=Note01>An unfused neural arch and long bone surface texture that is finely grooved, suggest that this individual is a juvenile.</ref>
}}
==References==
{{Reflist|2}}
{{Portal|Dinosaurs}}
{{Sauropodomorpha|S.}}
{{Taxonbar|from=Q427650}}
[[Category:Massopoda]]
[[Category:Dinosaur genera]]
[[Category:Sinemurian dinosaurs]]
[[Category:Pliensbachian dinosaurs]]
[[Category:Lufeng Formation]]
[[Category:Dinosaurs of China]]
[[Category:Fossil taxa described in 1942]]
[[Category:Fossil taxa described in 1951]]
[[Category:Fossil taxa described in 2007]]
[[Category:Taxa named by Yang Zhongjian]]
[[Category:Taxa named by Lü Junchang]]
[[Category:Taxa named by Dong Zhiming]]
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