Re-examination Of Chuanjiesaurus Anaensis (Sauropoda, Dinosauria) From The Chuanjie Formation (Middle Jurassic) In Lufeng Of Yunnan, China

The present study re-evaluates Chuanjiesaurus anaensis Fang et al., 2000 from the Middle Jurassic of Lufeng, Yunnan, Southwest China. The holotype and a new referred specimen are described in detail, and re-examined osteologically and phylogenetically. Based on close observations and comparisons, several emended diagnoses are proposed by the author. Some osteological features reveal Chuanjiesaurus belonging to Mamenchisauridae. Compared to other mamenchisaurid dinosaurs, Chuanjiesaurus anaensis possesses relatively primitive characters. The phylogenetic position of C. anaensis was analyzed. The data sets of some taxa from southwestern China were modified in the present research. The present analysis reveals that C. anaensis, Mamenchisaurus and Yuanmousaurus constitute a monophyletic group, which belongs to relatively derived Eusauropoda. This suggests that Mamenchisauridae could be positioned at more relatively derived part than previous thought. Primary Component Analysis of femur of some Sauropoda including Titanosauriformes shows morphological similarity between C. anaensis and Chinese Titanosauriformes. At the same time, the biogeography and evolutional history of sauropods, the gigantic herbivorous continental reptiles originated in Pangaea in the Late Triassic and moved to Laurasia later, are discussed. Based on the paleobiogeographical distributions and morphological similarity, the present study proposes a new hypothesis that C. anaensis could be an early in form of Asian Titanosauriformes, which moved from Europe before the separation of Asia from Europe during Aptian to Albian. Therefore, the present research deepens the understanding of evolution and paleobiogeography of Titanosauriformes in Asia during the Middle and Late Jurassic, and strengthens the significance of Chuanjiesaurus anaensis on the taxonomy of Mamenchisauridae.