''Tuojiangosaurus'' (meaning "Tuo River lizard") 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 ...

of herbivorous

stegosauria Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europ ...

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

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 ...

Period, recovered from the

Upper Shaximiao Formation The Shaximiao Formation () is a Middle to Late Jurassic aged geological formation in Sichuan, China, most notable for the wealth of dinosaurs fossils that have been excavated from its strata. The Shaximiao Formation is exposed in and around the ...

of what is now

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 ...

Province in

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 ...

Description

''Tuojiangosaurus'' was a large stegosaur, reaching in length and in body mass. Physically similar to the North American ''

Stegosaurus ''Stegosaurus'' (; ) is a genus of herbivorous, four-legged, armored dinosaur from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been fou ...

'', ''Tuojiangosaurus'' is the best understood of the Chinese stegosaurs. In 1977, Dong provided a diagnosis but this largely consisted of traits shared with other stegosaurus. In 1990,

Peter Malcolm Galton Peter Malcolm Galton (born 14 March 1942 in London) is a British vertebrate paleontologist who has to date written or co-written about 190 papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosaur ...

pointed out an

autapomorphy In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to ...

: the spines of the vertebrae of the tail base possess spines with bony skirts running from their front to the sides. ''Tuojiangosaurus'' has the typical narrow and low head, bulky body, and low teeth of other stegosaurids. The limbs, especially the arms, are rather short.Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 221 There are at least twenty-five dentary teeth. The teeth have a thick base, ''cingulum'', merging at the inside into a triangular vertical median ridge. The dorsal vertebrae have tall neural arches. The shoulder blade has a rectangular

acromion In human anatomy, the acromion (from Greek: ''akros'', "highest", ''ōmos'', "shoulder", plural: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process it extends laterally over the shoulder joint. The ...

.Galton, P.M., and P. Upchurch, 2004, "Stegosauria", pp. 343-362 in: D.B. Weishampel, P. Dodson, and H. Osmolska (eds.), ''The Dinosauria'', 2nd Edition. University of California Press, Berkeley, CA Tuojiangosaurus multispinus life restoration

Tuojiangosaurus multispinus life restoration

Like '' Kentrosaurus'', ''Tuojiangosaurus'' had two rows of plates along the spine, which became taller over the hip region. Those at the neck and front trunk were rounded or pear-shaped; the plates at the rear back became more triangular and pointed. All plates have a thickened central section, as if they were modified spikes. Dong estimated there were about seventeen pairs of plates and spikes. ''Tuojiangosaurus'' had at least two outward-pointing, rather robust, spikes on each side of the end of the tail, angled at approximately 45 degrees to the vertical. In stegosauridae, this spike arrangement has become affectionately known as the " thagomizer". Dong thought it were possible that there were four pairs of spikes. Paul, based on "''

Chungkingosaurus ''Chungkingosaurus'', meaning "Chongqing Lizard", is a genus of herbivorous dinosaur from the Late Jurassic Upper Shaximiao Formation in what is now China. It is a member of the Stegosauria. Description According to Dong e.a. the ''Chungkingo ...

'' sp. 3" specimen CV 00208, interpreted the thagomizer as a "pin-cushion array", with two vertical pairs of thick spikes and a third pair of narrow spikes pointing to behind.

Discovery

In 1974, during construction of the Wujiaba dam in

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 ...

, Sichuan, the remains of a stegosaurian were found. The type and only species of ''Tuojiangosaurus'', ''Tuojiangosaurus multispinus'', was named and described in 1977 (exactly a hundred years after the naming of ''

'' by

Othniel Charles Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among ...

) by

Dong Zhiming Dong Zhiming (Chinese: 董枝明, Pinyin: ''Dǒng Zhimíng''; born January 1937) is a Chinese vertebrate paleontologist formerly employed at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing. He began working at th ...

, Zhou Shiwu, Li Xuanmin and Chang Yijong. The generic name is derived from the River () Tuo. The specific name is derived from

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''multus'', "many", and ''spina'', "spine".Z. Dong, X. Li, S. Zhou and Y. Zhang, 1977, "On the stegosaurian remains from Zigong (Tzekung), Szechuan province", ''Vertebrata PalAsiatica'' 15(4): 307-312 Tuojiangosaurus at the Beijing Museum of Natural History

Tuojiangosaurus at the Beijing Museum of Natural History

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

, CV 209, was found in a layer of the Upper Shaximiao Formation, dating from the Oxfordian-

Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...

. It consists of a rather complete skeleton that however lacks parts of the skull, lower jaws, tail and limbs. In 1977, it represented the most complete stegosaurian skeleton found in Asia. The

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). O ...

was specimen CV 210, a

sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part o ...

. Subsequently, more material has been referred, including juveniles. This complemented the holotype with elements of the skull, especially the braincase, and the lower jaws. A mounted skeleton of ''Tuojiangosaurus multispinus'' is on display at the Municipal Museum of

Chongqing Chongqing ( or ; ; Sichuanese pronunciation: , Standard Mandarin pronunciation: ), alternately romanized as Chungking (), is a municipality in Southwest China. The official abbreviation of the city, "" (), was approved by the State Co ...

. In addition, a mounted cast is on display at the

Natural History Museum A natural history museum or museum of natural history is a scientific institution with natural history collections that include current and historical records of animals, plants, fungi, ecosystems, geology, paleontology, climatology, and more. ...

, in London. Another mount is displayed in the

Beijing Museum of Natural History The Beijing Museum of Natural History (BMNH; ) is located at 126 Tian Qiao Nan Street, Dongcheng District, Beijing, 100050, and is the most popular natural history museum in China.Yangchuanosaurus''. A cast of the original fossilised dinosaur skeleton, found at Wujiaba Quarry 1977 is also on display at

Bolton Museum Bolton Museum is a public museum and art gallery in the town of Bolton, England, owned by Bolton Metropolitan Borough Council. The museum is housed within the grade II listed Le Mans Crescent near Bolton Town Hall and shares its main entrance ...

, United Kingdom.

Classification

''Tuojiangosaurus'' was by Dong placed in Stegosauridae in 1977, more precisely in the Stegosaurinae. In 2004, a

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis by Galton recovered ''Tuojiangosaurus'' in a rather derived position, as a

sister species In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...

of '' Chialingosaurus''. An analysis by Octávio Mateus, Maidment, and Nicolai Christiansen, published in 2009, found that ''Tuojiangosaurus'' fell outside of Stegosauridae, though its exact position in Stegosauria (either as an early branching member of the group or a later branching species closer to stegosaurids) was uncertain due to the relatively fragmentary nature of the remains.Mateus, Maidment and Christiansen (2009). "A new long-necked ‘sauropod-mimic’ stegosaur and the evolution of the plated dinosaurs", ''Proc Biol Sci. 2009 May 22; 276(1663): 1815–1821. A more comprehensive analysis by Raven and Maidment in 2017 found that it grouped with ''

Huayangosaurus ''Huayangosaurus'' is a genus of stegosaurian dinosaur from the Middle Jurassic of China. The name derives from "Huayang" (華陽), an alternate name for Sichuan (the province where it was discovered), and "saurus", meaning "lizard". It lived ...

'' and its relatives.

Paleobiology

''Tuojiangosaurus'' ate low-lying, ground vegetation. Paul suggested that '' Chialingosaurus'' and ''

'' were in fact the juveniles of ''Tuojiangosaurus''.

Notes

References

* *

External links

Natural History Museum on ''Tuojiangosaurus''
{{Taxonbar, from=Q131098 Late Jurassic dinosaurs of Asia Stegosaurs Taxa named by Dong Zhiming Fossil taxa described in 1977 Paleontology in Sichuan Ornithischian genera