Evolution and innovation of the metazoan burrowing behaviour from Ediacaran-Cambrian transition, eastern Yunnan

The Precambrian–Cambrian transition represents a pivotal interval in Earth’s evolutionary history, marked by the demise of Ediacaran biota and the subsequent radiation of bilaterian organisms during the Cambrian Explosion. This study presents an integrated ichnological and sedimentological analysis of trace fossils across the Precambrian–Cambrian boundary interval in eastern Yunnan, South China, with the aim of reconstructing paleoecological dynamics and behavioral evolution during this critical transitional phase.Ichnotaxonomic diversity, architectural complexity, and tiering structure reveal a progressive intensification of metazoan–substrate interactions through the late Ediacaran. Trace fossils from this interval are predominantly horizontal and exhibit morphologies consistent with undermat-mining behaviors, indicating that benthic organisms were largely restricted to the mat-substrate interface. However, rare but distinct vertical burrows suggest the incipient development of exploratory and infaunal lifestyles.With the onset of the Cambrian, there is a notable increase in ichnodiversity, behavioral complexity, and substrate utilization, reflecting enhanced metazoan motility and ecological specialization. This period coincides with a shift from microbial-mat-dominated substrates to mixed-layer systems, driven by increasing bioturbation intensity. By Cambrian Stage 2, widespread bioturbation led to the progressive disruption of microbial mats and facilitated more extensive exploitation of three-dimensional ecological space.Benthic communities expanded their spatial occupation from surficial and semi-infaunal tiers into deeper substrate horizons, promoting greater ecological stratification and trophic complexity. These paleoecological transformations culminated in the replacement of Neoproterozoic-style matgrounds by Phanerozoic-type mix-grounds, representing a fundamental reorganization of marine ecosystems and a major milestone in the early ecosystem evolution of benthic communities.