Arthropod trace fossils from the Zhujiaqing Formation (Meishucunian, Yunnan) and their palaeobiological implications

摘要

Along with several non-arthropod ichnotaxa and rather non-specific scratchmarks, the Upper Phosphate of the Zhujiaqing Formation (Early Meishucunian Stage) in Eastern Yunnan yielded well-preserved resting and digging traces of the Rusophycus-type interpreted as resting traces of unknown large arthropods (ca. 3～6 cm in length). The discernible morphological details of these trace fossils enable a rough estimation of the body plan characteristics of the trace originators placing the latter doubtless into the early arthropods, if not euarthropods. The spectrum of the Meishucunian ichnoassemblage, especially the different types of arthropod repichnia point to the existence of a complex benthic ecosystem consisting of animals with different behavioural patterns and life styles already during the earliest Cambrian (Nemakit-Daldyn), and demands the assumption of a longer evolutionary past history of the benthic life on earth before the so-called "Cambrian Explosion" of the metazoans.