ABSTRACT

We present a revision of the referred specimen (LFGT LCD 9701–1) of Chuanjiesaurus anaensis from the Middle Jurassic Chuanjie Formation of Yunnan Province, southwest China, and demonstrate that LCD 9701-1 is differentiated from the holotype by numerous features. Therefore, it can be referred to a new taxon (Analong chuanjieensis gen. et sp. nov.). Analong bears a unique combination of characters, such as caudal transverse processes persisting until the 10th caudal (15th in Chuanjiesaurus); weakly developed posterior condylar ball in anterior caudal vertebrae (well developed in Chuanjiesaurus); ulnar anterolateral and anteromedial processes sub-equal in length and forming an angle of about 45 degrees (unequal in length and 60 degrees in Chuanjiesaurus anaensis); proximal width of metacarpal II 7% the length of radius (lowest value among mamenchisaurids); pubic distal width approximately 40% of its total length (greatest value among mamenchisaurids). Comparative study and cladistic analysis show Analong chuanjieensis is the earliest branching of Mamenchisauridae, while the (Mamenchisaurus + Chuanjiesaurus anaensis) branching is the latest branching of this clade. Our revision of Analong chuanjieensis increases the diversity of Mamenchisauridae and indicates the evolution of Mamenchisauridae is a complex than previously realised.