Yangchuanosaurus — Wikipédia

Yuangchuanosaurus (artist’s view).

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Genre

Yangchuanosaurus is a genre of dinosaurs theropods metricanthosauridae which lived in China during the average Jurassic, during the Bathonian and Callovian floors, and whose size and appearance were similar to those of Allosaurus , his parent of North America and Europe. Originally from the upper part of the formation of Shaximiao, he was the largest predator in a landscape including the Sauropods Mamenchisaurus And Omeisaurus and the stegosaurs Chialingosaurus , Tuylasaurus And Chungkingosaurus . He was appointed according to the region in which Yongchuan was discovered in China.

The specimen type of Y. shangyouensis had a skull 82 cm long and the total length of his body was estimated at around 8 m ^{[ first ]} . Another specimen, attributed to the new species Y. Magnus , was even larger, with a skull length of 1.11 m ^{[ 2 ]} . It could reach 10.8 m long and weigh up to 3.4 tonnes ^{[ 3 ]} . He had a bone crest on his nose and multiple small horns and crests, similar to those of Ceratosaurus .

Yangchuanosaurus was a powerful animal, a large meat eater. He was walking on two large muscular legs, had short arms, a strong and short neck, a large head with powerful jaws and large serrated teeth. He had a long massive tail which was about half of its length. The first finger of his foot was a small vestigial ergot. The three external toes were used to support the weight and each was equipped with a large label.

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Yangchuanosaurus shangyouensis tackle Tuojiangosaurus multispinus .

VND et al. (1978) appointed Yangchuanosaurus shangyouensis Based on the CV 00215, a complete skull and a skeleton that were taken from the formation of Shangshaximiao, near Yongchuan, Sichuan in China. It goes back to the Bathonian and Callovian floors of the average Jurassic, there are approximately 161.2-154 million years. It was discovered in June 1977 by a building worker when building the Shangyou tank dam. A second species of the same locality, Y. Magnus , was appointed by Dong et al. (1983) on the basis of the CV 00216, another complete skull and a skeleton. A detailed revision of the phylogeny of Tetanurae by Carrano, Benson & Sampson (2012) revealed that the two species are conspecific. Dong et al. (1978) and Dong et al. (1983) differentiated these species mainly on the basis of their size. In addition, Dong et al. (1983) noted that the upper maxilla of Y. Magnus had an additional window in the Antorbital pit, while Y. shangyouensis had only one pit in this place. However, it is considered an intraspecific variation, possibly ontogenetic. In addition, the apparent difference in the morphology of the cervical vertebrae can be explained by comparing different positions in the column. Consequently, the holotypes of the two species of Yangchuanosaurus are indeed identical and their codings are identical in the matrix of Carrano et al. (2012) ^{[ 4 ]} . Gregory S. Paul (1988) considered this kind in the same way as Metriacanthosaurus , but it was not supported.

Carrano et al. (2012) awarded a third specimen to Y. shangyouensis . The CV 00214 is represented by a partial postcranial skeleton without skull. He was collected in the career of Wujiaba, near the city of Zigong, Sichuan, China, in the lower part of the formation of Shangshaximiao. The CV 00214 was initially listed by Dong et al. (1978) in a fauna list as a new species of Szechuanosaurus , Szechunosaurs “Yestonensis” . There is no description or illustration, making S. “yandonensis” and name naked . Plus Tard, Dong et al. (1983) described it and attributed it to Szechunosarus Camp , a doubtful species which is only known by four teeth. Carrano et al. (2012) noted that the CV 00214 cannot be attributed to S. Campi Because the holotype materials of S. Campi (IVPP v.235, v.236, v.238, v.239; teeth) are not diagnostic. The teeth are kept in the CV 00214. A recent study by Daniel Chure CV 00214 (2001) concluded that he represented a new taxon, called informally “Szechuanoraptor Dong” , in which should also be integrated Szechuanosaurus zigongensis . However, the most recent revision (de Carrano et al. (2012)) suggests that CV 00214 and “S.” zigongensis cannot be conspecited because there is no autapomorphies shared with each other, and the latter comes from the underlying formation of Xiashaximiao. Phylogenetic analysis has shown that the CV 00214 was the most closely related to Y. shangyouensis And that, therefore, the first is assigned to him. Moreover, Szechuanosaurus zigongensis is closely linked to Y. shangyouensis and was therefore designated as the second species of Yangchuanosaurus ^{[ 5 ]} .

Yangchuanosaurus zigongensis is known from four specimens, including the ZDM 9011 (Holotype), a partial postcranian skeleton; ZDM 9012, a left maxilla; ZDM 9013, two teeth and ZDM 9014, a right posterior member. It was described for the first time by Gao (1993) and all specimens were collected in the Xiashaximiao training of the average Jurassic of Dashanpu’s career in Zigong, in Sichuan ^{[ 6 ]} .

In their 2018 study, C. Dal Sasso et al. retain Szechuanosaurus zigongensis to the detriment of Yangchuanosaurus zigongensis ^{[ 7 ] , [ 8 ]} .

In 2020, Chee Eng Goo published a study on a petrified embryo and appointed him Yangchuanosaurus longicollis ^{[ 9 ] , [ ten ]} .

A single species is recognized without ambiguity, Yangchuanosaurus shangyouensis ^{[ 11 ] , [ twelfth ]} .

A phylogenetic analysis of Carrano et al. (2012) concluded that Yangchuanosaurus was the most basal metricanthosaurida and the only non -metricanthosaurine metriacanthosaurida. The cladogram presented below follows their study ^{[ 13 ]} .

The cladogram presented below follows Zanno & Makovicky (2013) ^{[ 14 ]} .