Figure 1. Looping and meandering trace fossil Taphrhelminthopsis, made by a large Early Cambrian bioturbator, on a bedding plane from Lower Cambrian Poleta Formation, White-Inyo Mountains, California. Such traces, consisting of a central trough between lateral ridges, occur in sandstones deposited in shallow-marine environments. Evidence indicating original presence of microbial mats is found in associated strata, and morphological features of these traces suggest they were produced on seafloor by active ingestion, or perhaps grazing, of underlying sediments (Hagadorn et al., 2000).