''Yuanmousaurus'' ("Yuanmou lizard") was a

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their b ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

from the Middle

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...

period of

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. It is known from incomplete remains, recovered in 2000 from the Zhanghe Formation in

Yuanmou County Yuanmou County (; Yi script, Chuxiong Yi script: , International Phonetic Alphabet, IPA: ) is under the administration of the Chuxiong Yi Autonomous Prefecture, in the north of Yunnan province, China. It borders Wuding County to the east, Lufeng, ...

Yunnan Province Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

. ''Yuanmousaurus'' was a relatively large sauropod and may have reached about 17 meters (56 ft) in length. It was a basal member of the Sauropoda, but its exact systematic position is unclear. A recent study placed ''Yuanmousaurus'' within the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Mamenchisauridae Mamenchisauridae is a family of sauropod dinosaurs belonging to the Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa. Mamenchisaurids are characterized by their proportionately extremely long necks. Some members of the ...

. It may be a dubious genus. The only and

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

was ''Yuanmousaurus jiangyiensis''.

Description

''Yuanmousaurus'' was estimated to be approximately 17 meters (56 ft) in length. The skull is missing, while the neck is known only from a fragment of a posterior cervical vertebra. This fragment indicates elongated neck vertebrae, similar to those of mamenchisaurid sauropods, but unlike the much shorter neck vertebrae of the more basal ''

Shunosaurus ''Shunosaurus'', meaning "Lizard from Sichuan", is a genus of sauropod dinosaur from Late Jurassic ( Oxfordian) beds in Sichuan Province in China, from 161 to 157 Million years ago. The name derives from "Shu", an ancient name for the Sichuan pr ...

''. From the trunk and tail, nine dorsal, three sacral and seven caudal vertebrae were found. While the shoulder and pelvic girdles are missing with the exception of one ilium, the limbs are better known, including the

humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

thigh bone The femur (; : femurs or femora ), or thigh bone is the only bone in the thigh — the region of the lower limb between the hip and the knee. In many four-legged animals the femur is the upper bone of the hindleg. The top of the femur fits in ...

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

fibula The fibula (: fibulae or fibulas) or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. ...

astragalus Astragalus may refer to: * ''Astragalus'' (plant), a large genus of herbs and small shrubs *Astragalus (bone) The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...

, and a claw from the hind foot. The forelimbs were proportionally longer than in the shortnecked ''Shunosaurus'', but shorter than in ''

Omeisaurus ''Omeisaurus'' (meaning "Omei lizard") is a genus of sauropod dinosaur from the Middle 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 ...

'': the length ratio between humerus and thigh bone was 0.72 in ''Yuanmousaurus'', while it was 0.56 in ''Shunosaurus'' and 0.80 in ''Omeisaurus''.

Classification

''Yuanmousaurus'' is deemed to be a basal member of the

Eusauropoda Eusauropoda (meaning "True Lizard Foot") is a derived clade of sauropod dinosaurs. Eusauropods represent the node-based group that includes all descendant sauropods starting with the basal eusauropods of '' Shunosaurus'', and possibly '' Barapas ...

, standing outside the

Neosauropoda Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentina, Argentine paleontologist José Bonaparte and currently described as ''Saltasaurus loricatus'', ''Diplodocus longus'', and all animals directly descended from their most recent ...

, which comprises all more derived sauropods. In its

species description A species description is a formal scientific description of a newly encountered species, typically articulated through a scientific publication. Its purpose is to provide a clear description of a new species of organism and explain how it diff ...

Lü Junchang Lü Junchang (; 1965 – 9 October 2018) was a Chinese palaeontologist and professor at the Institute of Geology, Chinese Academy of Geological Sciences. An expert on Mesozoic reptiles, he described and named dozens of dinosaur and pterosaur taxa ...

and colleagues considered ''Yuanmousaurus'' a member of the

Euhelopodidae Euhelopodidae is a family of sauropod dinosaurs of disputed membership and affinities, which contains '' Euhelopus'' and its close relatives. Most proposed euhelopodids are from East Asia. Euhelopodidae was first recognized by Carl Wiman in 1929 ...

that was closely related to ''

Patagosaurus ''Patagosaurus'' (meaning "Patagonia lizard") is an extinct genus of eusauropod dinosaur from the Middle-Late Toarcian of Patagonia, Argentina. It was first found in deposits of the Cañadón Asfalto Formation, which date to around 179 to 177&n ...

'', more basal than ''

Euhelopus ''Euhelopus'' is a genus of sauropod dinosaur that lived between 145 and 133 million years ago during the Berriasian and Valanginian ages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. Lik ...

'', and more derived than ''

''. The Euhelopodidae, however, is abandoned by many palaeontologists since the systematic position of ''

'' itself is controversial. A newer analysis by Toru Sekiya places ''Yuanmousaurus'' within the Mamenchisauridae, together with ''

Mamenchisaurus ''Mamenchisaurus'' ( , or spelling pronunciation ) is an extinct genus of sauropod dinosaurs known for their remarkably long necks which made up nearly half the total body length. Numerous species have been assigned to the genus; however, the val ...

'', '' Tienshanosaurus'' and '' Chuanjiesaurus''. In 2013, a study describing the sauropod '' Nebulasaurus,'' also from the Zhanghe Formation, evaluated the characters distinguishing ''Yuanmousaurus'' and considered them invalid, since they were present in other sauropod taxa.

Discovery

The only skeleton (YMV 601) was recovered in May 2000 in the village Jiangyi in

. The excavation was led by palaeontologists of the Yunnan Provincial Institute of Cultural Relics and Archaeology, the Yuanmou Museum and the Chuxiong Museum. Today, the fossils are part of the Yuanmou Museum collection. They were described as ''Yuanmousaurus jiangyiensis'' by Lü Junchang and colleagues in 2006. The name adverts to Yuanmou County and the village Jiangyi, where the fossils were found.

References

External links

Archives of the Dinosaur Mailing List
{{Taxonbar, from=Q139201 Mamenchisauridae Dinosaur genera Aalenian dinosaurs Bajocian dinosaurs Dinosaurs of China Fossil taxa described in 2006 Taxa named by Lü Junchang Taxa named by Dong Zhiming