The type and only species, Chuanjiesaurus anaensis, was named by Fang, Pang, Lü, Zhang, Pan, Wang, Li and Cheng (2000) based on postcranial material discovered near Chuanjie (also rendered “Chuanjie”/“Ana”) village in Lufeng County, Yunnan, China.[1] The specific name refers to Ana (Chuanjie) village where the fossils were collected from Middle Jurassic red beds.[1][2]
Geological and temporal setting
Fossils of Chuanjiesaurus come from the Chuanjie Formation, a lacustrine to fluvio lacustrine succession in the Sichuan Yunnan Basin that overlies the Lower Jurassic Lufeng Formation and is Middle Jurassic in age (commonly interpreted as Aalenian–Bajocian to Bathonian–Callovian interval).[3][4] Stratigraphic work in the Lufeng region that established the Chuanjie Formation and its relationships was summarized by Fang et al. (2000).[1]
Description
Chuanjiesaurus is a large-bodied eusauropod with a long neck, low neural spines on the dorsal vertebrae, and mamenchisaurid-like cervical morphology as revised by Sekiya (2011).[2] Thomas R. Holtz Jr.’s compiled genus list reports a total length of roughly 25m (about 82ft) for Chuanjiesaurus.[5]
Classification
Detailed redescription places Chuanjiesaurus within Mamenchisauridae, based on features of the cervical and dorsal vertebrae and limb proportions.[2] Later study of a specimen once referred to Chuanjiesaurus resulted in its removal to a separate taxon, Analong chuanjieensis (a basal mamenchisaurid), underscoring that some historical referrals were composite.[6]
Paleoecology
The Chuanjie Formation preserves a dinosaur-bearing red-bed system with diverse ichnofaunas (theropod and sauropod tracks) and skeletal remains, indicating fluvio-lacustrine floodplain settings during the Middle Jurassic.[4] Coeval vertebrates from the unit include the metriacanthosaurid theropod Shidaisaurus jinae and additional sauropods such as Analong.[7]
History of research
The genus was established in 2000 alongside a revised stratigraphic framework for the Lufeng area.[1] A comprehensive osteological re-examination by Sekiya (2011) provided an emended diagnosis, anatomical comparisons, and a phylogenetic assessment that supported a mamenchisaurid affinity.[2] Subsequent work has refined the faunal composition of the Chuanjie Formation and clarified that some specimens historically referred to Chuanjiesaurus represent distinct taxa (e.g., Analong).[8][9]
Paleobiogeography and age
Regional syntheses place the Chuanjie and (time-equivalent) Shaximiao formations within the Bajocian–Callovian portion of the Middle Jurassic (ca. 178–165Ma radiometric bracket for portions of these units), consistent with the age inferred for Chuanjiesaurus horizons.[3][10][4]
Size
Popular technical compilations list a maximum length estimate of about 25m for Chuanjiesaurus, although individual size estimates vary due to the incompleteness of known material.[11][2]
References
1 2 3 4 5 Fang, X.; Pang, J.; Lü, J.; Zhang, Y.; Pan, Z.; Wang, Y.; Li, X.; Cheng, Z. (2000). "Lower, Middle, and Upper Jurassic subdivision in the Lufeng region, Yunnan Province"[Lower, Middle, and Upper Jurassic divisions of the Lufeng region of Yunnan Province](PDF). Proceedings of the Third National Stratigraphical Conference of China (in Chinese). Geological Publishing House: 208–214.
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