MEANING: Qianjiang lizard
PERIOD: Late Cretaceous
CONTINENT: Asia
Qianjiangsaurus is a hadrosauroid dinosaur from the Late Cretaceous of what is now China. While not a true hadrosaur, it exhibits some anatomical similarities that help to show the relationships between its basal relatives and the more derived hadrosaurids of East Asia. Qianjiangsaurus was a fairly large ornithopod, at about 8 m in length. It had a large beak, as well as batteries of teeth in the back of its mouth for processing its herbivorous diet.
Abstract from paper: A non-hadrosaurid hadrosauroid, Qianjiangsaurus changshengi gen. et sp. nov., is named and described here based on an incomplete, partially articulated skeleton from the top of the Upper Cretaceous Zhengyang Formation in Qianjiang District, Chongqing Municipality, southwest China. The skeleton displays a transitional morphology between non-hadrosaurid hadrosauroids and hadrosaurids. The diagnosis of the taxon is therefore defined as a unique combination of characters, including a series of plesiomorphic features typical of non-hadrosaurid hadrosauroids, some apomorphic features common among hadrosaurids but rarely reported in non-hadrosaurid hadrosauroids, and a probable autopomorphy, namely the fan-shaped prepubic process of the pubis strongly anteroposteriorly constricted and dorsoventrally expanded, with the length/height ratio of ∼0.79. Phylogenetic analysis recovers a sister-taxon relationship between Qianjiangsaurus and Plesiohadros outside of Hadrosauridae, and the clade consisting of the two taxa is positioned higher on the tree than Gobihadros and Gilmoreosaurus, but below the clade of Telmatosaurus + Tethyshadros, Eotrachodon and Zhanghenglong. Combining the morphological data with the phylogenetic topology identifies Q. changshengi as a late-branching non-hadrosaurid hadrosauroid. Given that the age assemblage of the eight hadrosauroids closely related to Qianjiangsaurus in phylogeny spans the Santonian–early Maastrichtian time interval, the top of the Zhengyang Formation, from which Qianjiangsaurus is recovered, is possibly restricted to the late Late Cretaceous in age. Hierarchical clustering of twelve hadrosauroid-bearing dinosaur assemblages from the Late Cretaceous deposits of Asia shows a strong correlation between the Zhengyang Formation and the Djadokhta and Baruungoyot formations in Mongolia that supports coeval interchange of dinosaur faunas across East Asia.
Qianjiangsaurus is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.
The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.
The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.
Qianjiangsaurus is an ornithopod. Ornithopoda is a clade of ornithischian dinosaurs that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous. They dominated the North American continent, then spread to Asia and eventually the southern hemisphere toward the end of the Cretaceous. Their major evolutionary advantage was their batteries of teeth, which allowed them to process vegetation in an extremely efficient way. Ornithopods were a diverse group, and included the hadrosaurs, which continued to dominate until the Cretaceous–Paleogene extinction event, which wiped out all non-avian dinosaurs.