''Zigongosaurus'' (meaning "

Zigong Zigong (, ), formed by the merger of the two former towns of Ziliujing (Tzuliuching, literally "self-flow well") and Gongjing (Kungching, literally "offering well"), is a prefecture-level city in Sichuan, southwestern China. Demographics Accord ...

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...

") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

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 Middle Jurassic is the second Epoch (geology), epoch of the Jurassic Period (geology), Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively ...

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

-age Shaximiao Formation of Zigong,

Sichuan Sichuan (; zh, c=, labels=no, ; zh, p=Sìchuān; alternatively romanized as Szechuan or Szechwan; formerly also referred to as "West China" or "Western China" by Protestant missions) is a province in Southwest China occupying most of t ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

. Because of incomplete knowledge of Jurassic Chinese sauropods, it has been hard to interpret, with some sources assigning it to '' Omeisaurus'', some to ''

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 ...

'', and some to its own genus.

History and taxonomy

The genus was based on CV 00261, a specimen including a partial

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

, and basioccipital (a bone from the

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

region). Additional bones from all areas of the skeleton, belonging to multiple individuals, were also described and assigned to the new genus. The authors thought it resembled ''Omeisaurus'', but was distinct based on

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

l details. Early accounts in the popular press suggested it was a brachiosaurid. Chinese sauropod taxonomy became increasingly convoluted in the 1980s. In 1983, Dong, Zhou, and Zhang named a species ''Omeisaurus fuxiensis'', which they based on different material than ''Zigongosaurus fuxiensis'', but then suggested that the two were the same animal. Following this, the genus was thought to belong to ''Omeisaurus'', possibly as a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are al ...

of ''O. junghsiensis''. In the mid-1990s, opinion shifted, and the genus was instead assigned, by Zhang and Chen, to ''Mamenchisaurus''. They noted that it came from a stratigraphic level between the usual ''Omeisaurus'' and ''Mamenchisaurus''

beds A bed is an item of furniture that is used as a place to sleep, rest, and relax. Most modern beds consist of a soft, cushioned mattress on a bed frame. The mattress rests either on a solid base, often wood slats, or a sprung base. Many be ...

in age, but more closely resembled ''Mamenchisaurus''. In particular, the

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

of the vertebrae (the part of the vertebra that sticks up, over the passage for the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

) in both genera have distinctive weak bifurcation, or splitting, that is not found in ''Omeisaurus''. The authors renamed it ''Mamenchisaurus fuxiensis''. This assignment was followed provisionally in the most recent major review of sauropods, but at least one author (Valérie Martin-Rolland) has found it to be a distinct genus.

Paleobiology

Whichever genus it turns out to be, as a mamenchisaur- or omeisaur-like sauropod it would have been a large,

quadrupedal Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor ...

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpar ...

with a long neck. It is regarded as a medium- to large-sized sauropod, with a length of around 15 meters (50 feet).

References

{{Taxonbar, from=Q135036 Mamenchisaurids Jurassic dinosaurs of Asia Fossil taxa described in 1976