First Occurrence of Wronascolex sp. (Palaeoscolecida, Priapulida) in the Cambrian Tianpeng Formation (Wuliuan Stage), Southeastern Yunnan, South China: Implications for a New Burgess Shale-Type Lagerstätte

We report the discovery of a new palaeoscolecid worm specimen from the Bainiuchang area, southeastern Yunnan, China. The specimen exhibits a cylindrical body with annulations, each bearing two rows of Hadimopanella-type sclerites, along with plates, platelets, microplates, and implanted plates. These features are compatible with the diagnosis of the genus Wronascolex, and the specimen is tentatively assigned to Wronascolex sp. However, given the limited number and preservation of the available specimens, which preclude a detailed demonstration of the scleritome morphology for comparison with other palaeoscolecid worms, this assignment should be treated as tentative. This specimen may be the first record of a soft-bodied fossil from the Miaolingian Series (Wuliuan Stage) strata of southeastern Yunnan. Its taphonomic features—preservation as carbonaceous compressions accompanied by iron-rich films—are broadly consistent with Burgess Shale-type (BST) preservation. Whole-rock geochemical analysis of samples from the fossil-bearing interval yielded redox proxy values suggestive of suboxic to weakly reducing depositional conditions, broadly comparable to those reported from some BST deposits, such as the Mackenzie Mountains locality of Canada. However, these geochemical results are preliminary and based on a limited number of samples. Taken together, these observations suggest the possibility that the Bainiuchang area may host a BST Lagerstätte. Should this be confirmed, such a deposit would postdate the Chengjiang and Guanshan biotas (Cambrian Series 2, eastern Yunnan) and predate the Fulu biota, which is the only confirmed BST Lagerstätte in southeastern Yunnan to date. Furthermore, this discovery extends the known paleogeographic range of the genus Wronascolex southward to the southwestern margin of the South China Block. It also represents, to our knowledge, the first reported occurrence of soft-bodied fossil preservation in the Wuliuan Stage of Yunnan Province.