Yangchuanosaurus (Yangchuan lizard)
Yangchuanosaurus (Yangchuan lizard)
Named By : Dong et al - 1978
Diet : Carnivore
Size : Estimated 10 meters long
Type of Dinosaur : Large Theropod
Type Species : Y. shangyouensis (type), Y. zigongensis
Found in : China - Shaximiao Formation
When it Lived : Late Jurassic, 160-144 million years ago
Yangchuanosaurus was an extinct species belonging to the metriacanthosaurid theropod dinosaurs which was found in China during to the Middle through the Late Jurassic periods (Bathonian to Oxfordian stages) and was comparable in dimensions as well as appearance North American and European relative, Allosaurus. Yangchuanosaurus is part of the Upper Shaximiao Formation and was the largest predator of the landscape which included sauropods Mamenchisaurus and Omeisaurus as well as the Stegosaurs Chialingosaurus, Tuojiangosaurus and Chungkingosaurus. The theropod is named in honor of the area where it was first discovered, Yongchuan, in China.
Jim, the Photographer from Springfield PA, United States of America, CC BY 2.0, via Wikimedia Commons
Dong et al. (1978) designated Yangchuanosaurus shangyouensis in reference to CV 0215, a fully-constructed skull and skeleton that was taken from the Shangshaximiao Formation, near Yongchuan, Yongchuan District, Sichuan. It is from the Oxfordian phase in the Late Jurassic period, about 161.2 to 157.3 million years ago. It was first discovered during the month of June in 1977, by an employee in work on the Shangyou Reservoir Dam. Another species found in the same region, Y. magnus, was identified by Dong and co. (1983) using CV 00216, a complete skull and skull. A thorough revision of the tetanuran’s phylogeny by Carrano, Benson & Sampson (2012) discovered they are consensual. Dong et al. (1978) as well as Dong and co. (1983) identified the species by size. In addition, Dong et al. (1983) pointed out the fact that the maxilla in Y. magnus is characterized by an additional fenestra in the antorbital fossa. Y. shhangyouensis had only an antorbital fossa. But, it’s believed to be an interspecific and possibly ontogenetic variation. Additionally, the apparent differences in cervical vertebral anatomy can be explained by looking at the different locations in the column. Therefore, the holotypes of these two types of Yangchuanosaurus are actually identical, and their codes are similar in the Carrano and colleagues. (2012) matrix. Gregory S. Paul (1988) believed that this genus was as the same as Metriacanthosaurus however, this is not accepted as a valid argument.
Carrano et al. (2012) assigned the third instance for Y. shangyouensis. CV 00214 is represented as the partial postcranial skull that does not contain the skull. It was discovered within the Wujiaba Quarry located near Zigong city in Sichuan located in the southern region of the Shangshaximiao Formation. CV 00214 was first described in Dong et al. (1978) as a flora list as a brand new type from Szechuanosaurus, Szechuanosaurus “yandonensis”. There is no description nor image of the species, which makes S. “yandonensis” a nomen nudum. Later, Dong et al. (1983) identified it, and classified it as Szechuanosaurus campi. It is a questionable species, which is only known by four teeth. Carrano et al. (2012) stated that CV 00214 isn’t able to be classified as S. campi due to the fact that the holotype materials from S. campi (IVPP V.235, V.236, V.238, V.239; teeth) are not diagnostic and no teeth have been retained within CV 00214. A recent re-analysis of CV 00214 by Daniel Chure (2001) concluded that it was a new taxon, formally referred to as “Szechuanoraptor dongi”, into which Szechuanosaurus Zigongensis was also subsumed. However in the latest version (by Carrano et al. (2012)) indicated it is possible that CV 01214 as well as “S.” zigongensis cannot be considered co-specific since there aren’t any autapomorphies that share between both, and the former is derived from the Xiashaximiao Formation. A phylogenetic study revealed CV 01214 to be the one most closely associated with Y. shangyouensis, and therefore, the former can be assigned to it. In addition, Szechuanosaurus zigongensis was found to be closely connected to Y. shangyouensis and therefore was named an additional species belonging to Yangchuanosaurus.
Yangchuanosaurus zigongensis is recognized from four specimens , including ZDM 9011 (holotype) A partial postcranial skeleton ZDM 9012, left-hand maxilla ZDM 9013 two teeth, along with ZDM 9014, an a hind limb of the right. The first time it was described was in 1993 by Gao (1993) as well as all of the specimens taken in the Middle Jurassic Xiashaximiao Formation in the Dashanpu Dinosaur Quarry of Zigong, Sichuan.