A revision of the referred specimen of Chuanjiesaurus anaensis Fang et al., 2000: a new early branching mamenchisaurid sauropod from the Middle Jurassic of China

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.

KEYWORDS:

• Chuanjie
• Yunnan
• middle Jurassic
• Chuanjie Formation
• Mamenchisauridae
• Analong

Acknowledgments

For their hospitality and access to specimens in their care, we wish to thank Luo JY, Yue SK, Yue SB, Wang H, Wang Q, and Pan SG . Ren Xin-Xin wishes to thank Dong ZM for his generous helping during the first research trip to Lufeng World Dinosaur Valley. We are grateful to C. Suarez (UARK) for helpful discussion and revision. Thoughtful reviews by anonymous reviewers, and the editor improved an earlier version of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study is supported by grant from The Strategic Priority Research Program of Chinese Academy of Sciences (Grant number: XDB26000000) and National Natural Science Foundation of China (Grant numbers: 41688103, 41872021).