A fossil arthropod similar to Fuxianhuia and displaying an exceptionally well-preserved alimentary canal with in situ gut contents is reported from the lower Middle Cambrian (ca. 510 Myr ago) of South China. Three-dimensionally preserved, paired phosphatic nodules, arranged in series along both sides of the gut and containing spherical bacteria, probably represent serial digestive glands. The gut is filled with fragments of the eodiscoid trilobite, Pagetia. The well-developed digestive glands and the fragmentary trilobite remains suggest (i) that the arthropod was a durophagous, possibly selective predator, and (ii) that small trilobites such as eodiscoids were a major food source in Cambrian marine ecosystems. This fossil association augments the small number of previously described associations providing more or less direct evidence of predator-prey relationships in Cambrian epibenthic communities.