Mazongshan dinosaur assemblage from late Early Cretaceous of northwest China
The Early Cretaceous (144–99 million years age) was a transitional interval in the Earth's evolving terrestrial biota, that witnessed the rise of angiosperm plants, emergence of modern orders of pollinating flies, rapid turnover among major groups of dinosaurs, early radiation of major clades of birds, and diversification of major groups of mammals. This dissertation provides a snapshot of the dinosaur world during the Albian (Late Early Cretaceous) of the Ma-Zong-Shan area, northwest China. Chapter 1 provides an overview of the Sino-American Horse Mane Mountain Dinosaur Project, that was conducted over four years (1997–2000) of field work from which the stratigraphical and paleontological data on which this dissertation is based mainly were collected. The following three chapters focus on three herbivorous dinosaurs from the Ma-Zong-Shan area. Chapter 2 studies Archaeoceratops oshimai Dong et Azuma, 1997, a basal horned dinosaur. Phylogenetic analysis reveals a different, dual evolutionary scenario for the derived Late Cretaceous horned dinosaurs in Asia and North American, respectively. Chapter 3 studies Equijubus normani, gen. et sp. nov., which is represented by a complete skull and mandible, and partial postcranial material. Phylogenetic analysis illustrates that Equijubus is the earliest known duck-billed dinosaur (Hadrosauroidea), and important changes in the facial portion occurred during the early evolution of this group. Chapter 4 studies Gobititan shenzhouensis, gen. et sp. nov., which preserves an almost complete series of caudal vertebrae and left hind limb. Gobititan represents the first Early Cretaceous titanosaur dinosaur from China.