Well-preserved arthropod trackways are found in the Lower Triassic Daye Formation in the Huaxi area of the city of Guiyang, South China. Two types of trackways have been identified. The first type is composed of symmetrical to asymmetrical trackways containing several sets of repeated imprints. The main imprints in each set are typically tetradactyl at the front of the imprint and bifid towards the rear. Associated intermediate imprints are simple, short to long, curved scratches with a bifid termination on one end. The second type is composed of irregularly arranged imprints of variable morphologies. The morphological characteristics of both types of trackways suggest that these trace fossils should be referred to as Kouphichnium, which is most probably produced by limulids, marine arthropods that inhabit a wide range of marginal marine environments during their life cycle. The Kouphichnium specimens documented here are the earliest limulid fossil trackways found after the Permian–Triassic mass extinction (PTME) in South China. Both forms of limulid traces are closely associated with other ichnotaxa, including Helminthoidichnites, Helminthopsis, Planolites, and Phycosiphon, which indicates the emergence of a three trophic level system with limulids located at the top of the food web during the Dienerian (251.7–251.2 Ma). Paleoenvironmental analysis reveals that the trace-makers lived below fair-weather wave base, on a gently sloping bottom, at depths of about 50–60 m, while pyrite framboid data suggest that deposition occurred under dysoxic conditions. The complexity of the Dienerian food web and feeding behaviors is a reflection of the degree of marine benthic ecosystem recovery and a result of the environmental amelioration after the PTME.
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Vol. 34 • No. 4