''Tonganosaurus'' (named for the town of Tong'an, Sichuan where it was found) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of mamenchisaurid

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 ...

, similar to ''

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 ...

''. It is known from one specimen consisting of twenty vertebrae, a front limb and pectoral girdle, and a complete hind limb with partial hip. It was discovered in the Yimen Formation,

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 ...

. The horizon of the specimen and the age of the Yimen Formation is controversial. The formation has been divided into three levels, and ''Tonganosaurus'' appears to be of late Early Jurassic (

Pliensbachian The Pliensbachian is an age of the geologic timescale and stage in the stratigraphic column. It is part of the Early or Lower Jurassic Epoch or Series and spans the time between 192.9 ±0.3 Ma and 184.2 ±0.3 Ma (million years ago). The Plie ...

) age. ''Tonganosaurus'' is the oldest known member of the mamenchisaurids, being almost 15 million years older than the next-oldest members of the group. It was first named by Li Kui, Yang Chun-Yan, Liu Jian and Wang Zheng-Xin in

2010 The year saw a multitude of natural and environmental disasters such as the 2010 Haiti earthquake, the Deepwater Horizon oil spill, and the 2010 Chile earthquake. The 2009 swine flu pandemic, swine flu pandemic which began the previous year ...

and the

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 ...

is ''Tonganosaurus hei''.

Description

The ratio of the front and rear limbs is 0.80. The tibia was straight and thick, with a length 75% that of the femur. The holotype is an incomplete skeleton of an adult sauropod. The skeleton of ''Tonganosaurus'' has been calculated in size, using ''

'' as reference, at long. In life, it was probably a little bigger, about .

History of discovery

In 2007, the Chengdu University of Technology Museum based on information gathered from citizen scientists, searched for dinosaurs in Tongan Town,

Huili County Huili ( zh, s=会理市, p=Huìlǐ Shì; Yi: or ''nyi ddix shyp'' or ''hop li shyp'') is a county-level city of far southern Sichuan province, China. It is under the administration of the Liangshan Yi Autonomous Prefecture. Formerly Huili C ...

Sichuan Province Sichuan is a Provinces of China, province in Southwestern China, occupying the Sichuan Basin and Tibetan Plateau—between the Jinsha River to the west, the Daba Mountains to the north, and the Yunnan–Guizhou Plateau to the south. Its capita ...

. They found the fossils of ''Tonganosaurus'' in the middle of the lower part of the Yimen Formation, whose age is estimated on 184.5 Ma. The fossils included about 20 vertebrae, a complete right shoulder blade and right forelimb, a distal left humerus, intact left and right ischia, a left femur, and complete right hind limb, and more than 10 scattered cervical vertebrae, ribs, tibia and claw bones. The fossils were collected in the same general area and were proportional, so they were believed to belong to the same animal. Being the first representative of the family

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 ...

implies a high diversity of sauropods in the late Early Jurassic. The specimen was kept at Chengdu University of Technology Museum, with the number MCDUT 14454.

Paleoenvironment

''Tonganosaurus'' holotype comes from the Upper section of the Yimen Formation, being associated with ''

Brontopodus ''Brontopodus'' is an ichnogenus of dinosaur footprint by sauropod trackmaker. This ichnogenus is mainly characterized by a wide-gauge trackway, which is distinguishable from narrow-gauge sauropod tracks like '' Breviparopus'' or '' Parabrontopod ...

'' tracks with also Mamenchisaurid resemblance, that maybe were made by this taxon. These layers are also filled with

Ostracoda Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant) have been identified,Brandão, S.N.; Antonietto, L.S; Nery, D.G.; Santos, S.G.; Karano ...

ns (''

Darwinula ''Darwinula'' is a genus of ostracods belonging to the family Darwinulidae. Species: * ''Darwinula aurea'' * ''Darwinula stevensoni ''Darwinula'' is a genus of ostracods belonging to the family Darwinulidae. Species: * ''Darwinula aurea ' ...

''),

Stonewort Charales is an order of freshwater green algae in the division Charophyta, class Charophyceae, commonly known as stoneworts. Depending on the treatment of the genus '' Nitellopsis'', living (extant) species are placed into either one family ( ...

Bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

s ('' Utschamiella'' and '' Sibireconcha'') and Conchostracans. The Stonewort assemblage is dominated by the genus '' Aclistochara'' (''A. nuguishanensis'', ''A. yunnanensis'') associated with elements of '' Porochara'' and sporadic individuals of '' Stenochara'', suggesting shallow-deep lake and flood environments. Apart from ''Tonganosaurus'', Sauropodomorph remains where uncovered, likely similar to ''

Yunnanosaurus ''Yunnanosaurus'' ( ) 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-buil ...

'' of the same age.

References

{{Taxonbar, from=Q133174 Mamenchisauridae Dinosaur genera Pliensbachian dinosaurs Fossil taxa described in 2010 Dinosaurs of China