A COMPLETE SKELETON OF A BASAL SAUROPOD DINOSAUR FROM THE EARLY JURASSIC OF CHINA AND THE ORIGIN OF SAUROPODA

Sauropods were very successful group of herbivorous dinosaurs in terrestrial ecosystems, but their early evolution is poorly understood because of a highly incomplete fossil record. Characterizing the evolutionary history of early sauropods is central to understanding their rise and diversification in the Jurassic and Cretaceous. Here we report the discovery of a nearly complete and exquisitely preserved skeleton of a basal sauropod from the Lower Lufeng Formation (Early Jurassic) in Yunnan, China that fills a critical gap in the early evolution of sauropod dinosaurs. The new taxon, <i>Yizhousaurus sunae</i> gen. et sp. nov., is the most complete basal sauropod currently known with intact skull; it is an important transitional fossil documenting the evolution of sauropods from prosauropods. The skull of <i>Yizhousaurus</i> is particularly significant because basal sauropods are diagnosed solely on the basis of fragmentary postcranial material. The new material reveals a mosaic of plesiomorphic and derived features that clarify early sauropod evolution, increase our anatomical knowledge of basal sauropods, and shed new light on their patterns of early diversifications.