''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 ...

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

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 Mya. The J ...

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

Yuanmou County Yuanmou County (; Chuxiong Yi script: , IPA: ) is under the administration of the Chuxiong Yi Autonomous Prefecture, in the north of Yunnan province, China, bordering Sichuan province to the north. The famous Yuanmou Man Yuanmou Man (, ' ...

Yunnan Province Yunnan , () is a landlocked province in the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is Kunming. The province borders the C ...

. ''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 la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Mamenchisauridae Mamenchisauridae is a family of sauropod dinosaurs belonging to Eusauropoda known from the Jurassic and Early Cretaceous of Asia and Africa. Some members of the group reached gigantic sizes, amongst the largest of all sauropods. Classification T ...

. The only and

type species In 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 species that contains the biological type specimen( ...

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 "shu lizard", is a genus of sauropod dinosaur from Late Jurassic ( Oxfordian) beds in Sichuan Province in China, approximately 159±2 million years ago. The name derives from "Shu", an ancient name for the Sichuan ...

''. 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 (; ) 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 and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...

radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...

thigh bone The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with t ...

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

fibula The fibula or calf bone is a human leg, leg bone on the Lateral (anatomy), 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 ...

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to te ...

, 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 Jurassic Period (Bathonian-Callovian stage) of what is now China. Its name comes from Mount Emei, where it was discovered in the lower Shaximiao Formation o ...

'': 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 sauropods") 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 ''Barapasaurus ...

, standing outside the

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

, which comprises all more derived sauropods. In its

species description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

, Lü Junchang 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&nb ...

'', 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 stages of the Early Cretaceous in what is now Shandong Province in China. It was a large quadrupedal herbivore. ...

'', 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 a genus of sauropod dinosaur known for their remarkably long necks which made up nearly half the total body length. Numerous species have been assigned to the genus; however, many of these might ...

'', '' Tienshanosaurus'' and '' Chuanjiesaurus''.

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 Middle Jurassic dinosaurs of Asia Mamenchisaurids Fossil taxa described in 2006 Paleontology in Yunnan Taxa named by Lü Junchang