A Diverse Fossil Assemblage Associated with the First Appearance of Parabadiella Huoi from the Meishucun Section (cambrian Stage 3, South China)

The base of the Cambrian Series 2 (Stage 3) is generally associated with the first appearance of trilobites. However, its global correlation remains a challenge due to diachroneity, facies control, and stratigraphic incompleteness. In South China, Parabadiella huoi is widely regarded as the earliest trilobite and marks the first appearance of trilobites in the region. Here, we report a taxonomically diverse fossil assemblage associated with the first occurrence of P.huoi from the lowermost Bed 13 of the Yu’anshan Formation at the Meishucun section (Yunnan, South China). The assemblage comprises linguliform brachiopods (Eoobolus sp., Botsfordia minuta), bradoriids, hyoliths, chancelloriids, and Microdictyon, etc. It provides a well-constrained record of a diverse community associated with the earliest trilobite occurrence in South China. This assemblage documents a rapid faunal transition from tubular-dominated small shelly fossil communities to more taxonomically and ecologically complex benthic ecosystems. The co-occurrence of mobile arthropods, sessile suspension feeders, and skeletal metazoans indicates an increasing ecological differentiation and community structuring at the onset of Stage 3. These results imply that the first appearance of trilobites in South China reflects not only a biostratigraphic datum but also a broader ecological bioevent. Enhanced documentation of this interval provides a refined framework for correlating trilobite-bearing strata across South China and facilitates comparison with coeval successions in Australia, Siberia, West Gondwana, and Laurentia.