Trace Fossil Community Cruziana rugosa, sedimentary environment and ecological characteristics in the top of the Early Ordovician Hongshiya Formation in Erchun, Kunming

Cruziana and its related trace fossils usually were formed on sediment surface by benthic trilobite resting and creeping in subtidal zone to neritic continental shelf area,which could indicate ancient water depth. In this paper, the sedimentary environment analysis on the trace fossil community Cruziana rugosa in the top of the Early Ordovician Hongshiya Formation in Erchun, Kunming neritic continental, Yunnan Province shows that the sedimentary environment of trace fossil community Cruziana rugosa occurrs from the supratidal zone to the intertidal zone, indicating that trilobites could live in the short-term exposuring environment. This adaptive activity of trilobites may be the evolution preparation for the arthropods advancing from the ocean to the land.