Dense early Cambrian Psammichnites gigas circularis from South China and its palaeoecological significance for the Cambrian Information Revolution

The Cambrian Stage 3 hongjingshao Formation of the Sanjiezi section at Yunnan Province, South China, provides a new window to explore the fine morphology of Psammichnites gigas circularis and discuss the role of its producer as a bulldozer in the deep transformation that took place in benthic ecology during the early Phanerozoic. Psammichnites gigas circularis is locally abundant in shallow-marine fine-grained sandstone from the uppermost strata of this formation. This ichnotaxon comprises horizontal, bilobate, sinuous to irregular meandering, looping burrows bearing a distinct median dorsal menisci/groove and is typically preserved on sandstone tops. Scanning electron microscopy-Energy dispersive X-ray spectroscopy (SEM-EDS) analysis indicates that the backfill consists of clay minerals elements of Al and Si, whereas the surrounding matrix is dominated by Ba, S, Al and Si. This study also demonstrates that dense Psammichnites gigas circularis occur in the Cambrian Stage 3 strata reflected strophotactic and thigmotactic behaviours of trace makers, indicating that these producers may have possessed advanced foraging capabilities, which are indicative of the signal characteristics associated with the Cambrian Information Revolution. The bulldozers that produced Psammichnites gigas circularis colonised mobile sandy substrate in shallow marine sand-dominated settings.