Chinshakiangosaurus (Chinshakian lizard)
Chinshakiangosaurus (Chinshakian lizard)
Named By : Ye vide Dong - 1992
Diet : Herbivore
Size : Estimated 11-13 meters long
Type of Dinosaur : Sauropod
Type Species : C. chunghoensis (type)
Found in : China - Fengjiahe Formation
When it Lived : Late Jurassic, 159-142 million years ago
Chinshakiangosaurus (JIN-shah-jiahng-uh-SOR-us, meaning “Chinshakiang lizard”) is a genus of dinosaur and probably one of the most basal sauropods known. The sole kind, Chinshakiangosaurus chunghoensis, is identified from a skeleton fragment discovered inside Lower Jurassic rocks in China. Chinshakiangosaurus is among the rare basal sauropods that have preserved skull bones. This is crucial to understanding the evolution in this particular group. It indicates that early sauropods might have had cheeks that were fleshy.
Like all sauropods it was a huge herbivore, quadrupedal, with a large lengths of tail and neck. The length of the body of the sole specimen is believed to be 12-13 meters. The remains consist of dentary (the tooth-bearing bone of the mandible) comprising teeth as well as a few components that comprise the postcranium. At present only the dentary and the teeth were extensively studied and the rest of the skeleton needs to be described.
The dentary was curled in dorsal-facing view, meaning that the mandibles created the shape of a broad, U-shaped snout. This is a common feature in sauropods. Prosauropods however, in contrast their dentary was straight with a V-shaped narrow snout. Paul Upchurch and colleagues (2007) think that this distinction may provide clues to feeding practices: The prosauropods sporting their snouts that were tapered may have been selective feeders who consumed only certain parts of the plant, and sauropods that had broad snouts were bulk eaters who were adapted to eat huge amounts of foliage.
The size of the teeth was larger towards the top of the snout, similar to in sauropods. Another sauropod-like feature was a bony snout that was affixed to the teeth laterally and got thicker towards the top of the snout. The plate could have prevented the teeth from being displaced during defoliation of plants.
Dentary depth was quite deep. In prosauropods, however it lowered towards the snout’s tip and in sauropods, the dentary got more deep, creating a deep symphysis. When viewed from a lateral angle the dentary displays a distinct ridge running along the entire bone. Aside from Chinshakiangosaurus it is only found in prosauropods. There, it is thought to be the point of entry for cheeks that are fleshy. The cheeks of this kind would have stopped food from falling out of the mouth. It could also indicate that the food was subjected to a amount of processing in the mouth before it was consumed. If Chinshakiangosaurus is indeed the basal sauropod, this is the first instance of cheeks within this group. In all sauropods identified from congruous remains, this characteristic was reduced before.
On both sides of the mandible, there were 19 teeth, more than any other sauropods, however less than those found in the prosauropod Plateosaurus. They were lanceolate, and equipped with coarse denticles, with them, they resembled those of prosauropods much more than of sauropods. The lingual part of the teeth was slightly concave. This could have been an initial condition towards very concave, spoon-shaped teeth typical of sauropods.
The fossils were discovered in the year 1970 through Zhao Xijin and colleagues in Yongren County in central Yunnan. They’re part of the Fengjiahe Formation which is composed of siltstones, mudstones and sandstones, which were laid down fluvolacustrine (inside lakes and rivers). Fossils of invertebrates such as bivalves and ostracodes were used to establish these sediments to be Upper Jurassic in age. An exact dating was not possible.
The Holotype sample (IVPP V14474) is comprised of one left dentary cervical and a few dorsal as well as caudal vertebrae. They also have both scapulae and pelvic bones, and hind legs. C. H. Ye identified the specimen in 1975 under the Chinshakiangosaurus chunghoensis (after the Yangtze River and the village Zhonghe). However, as the specimen did not include any description of the fossils and the name was not a name that was Nudum (nacked the name) prior to the time Dong Zhiming published a short description in 1992. Since the time, the authorship has been correctly identified by the name of “Chinshakiangosaurus chunghoensis Ye vide Dong, 1992”.
After Dong’s descriptionof the genus, this Genus, although possible, was not recognized by paleontologists in general. It was discovered by Upchurch and coworkers (2004) which classified it as an nomen dubium in Sauropoda. In 2007 Upchurch and co-workers published a detailed description of the dentary as well as the teeth, and declared Chinshakiangosaurus as an appropriate taxon.