Жоңчуаньзавр: Қытайдың Орта Юра заманының жыртқыш динозавры

Metriacanthosaurid theropod dinosaur genus from Middle Jurassic period. Yangchuanosaurus is an extinct genus of metriacanthosaurid theropod dinosaur that lived in China from the Middle Jurassic to Early Cretaceous periods (Bathonian to Berriasian stages), and was similar in size and appearance to its North American and European relative, Allosaurus. Yangchuanosaurus hails from the Upper Shaximiao Formation and Suining Formation and was the largest predator in a landscape that included the sauropods Mamenchisaurus and Omeisaurus and the stegosaurs Chialingosaurus, Tuojiangosaurus and Chungkingosaurus. This theropod was named after the area in which was discovered, Yongchuan, in China.

Dong et al. (1978) named Yangchuanosaurus shangyouensis on the basis of CV 00215, a complete skull and skeleton which was collected from the Shangshaximiao Formation, near Yongchuan, Yongchuan District, Sichuan. It dates to the Oxfordian stage of the Late Jurassic period, about 161.2 to 157.3 million years ago. It was discovered in June 1977 by a construction worker during the construction of the Shangyou Reservoir Dam. A second species from the same locality, Y. magnus, was named by Dong et al. (1983) on the basis of CV 00216, another complete skull and skeleton. A detailed revision of tetanuran phylogeny by Carrano, Benson & Sampson (2012) revealed that both species are conspecific. Dong et al. (1978) and Dong et al. (1983) differentiated these species primarily on the basis of size. In addition, Dong et al. (1983) noted that the maxilla of Y. magnus has an additional fenestra within the antorbital fossa, whereas Y. shangyouensis possessed only a fossa in this location. However, it is considered to be an intraspecific, possibly ontogenetic, variation. Furthermore, the apparent difference in cervical vertebral morphology can be explained by comparing different positions within the column. Hence, the holotypes of the two species of Yangchuanosaurus are effectively identical, and their codings are identical in Carrano et al. (2012) matrix. Gregory S. Paul (1988) regarded this genus as a synonym of Metriacanthosaurus, but this has not been supported. A third, informal species, Yangchuanosaurus "longqiaoensis", was briefly mentioned in a faunal listing of the Penglaizhen Formation (initially believed to date to the Late Jurassic but is probably Early Cretaceous (Berriasian – Valanginian) in age) by Li, Zhang and Cai (1999). However, since it was published solely in a faunal list and not described in detail, it is a nomen nudum and is questionably referable to Yangchuanosaurus. Remains assigned to Yangchuanosaurus sp. were recovered from the Berriasian Suining Formation in 1966.

The type specimen of Y. shangyouensis had a skull long, and its total body length was estimated at Another specimen, assigned to the new species Y. magnus, was even larger, with a skull length of It may have been up to long, and weighed as much as Gregory S. Paul suggested that these are the same species and gave a length of 11 meters (36 feet) and a weight of 3 metric tons (3.3 short tons). There was a bony ridge on its nose and multiple hornlets and ridges, similar to Ceratosaurus. Yangchuanosaurus was a large, powerful meat eater. It walked on two large, muscular legs, had short arms, a strong, short neck, a big head with powerful jaws, and large, serrated teeth. It had a long, massive tail that was about half of its length. The first digit of its foot was a small dewclaw. The three outer toes were used to bear weight and each was equipped with a large claw.

A phylogenetic analysis by Carrano et al. (2012) found Yangchuanosaurus to be the basalmost known metriacanthosaurid and the only non metriacanthosaurine metriacanthosaurid. The cladogram presented below follows their study.