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Non-marine arthropod traces from the subaerial Ordovician Borrowdale Volcanic Group, English Lake District

Abstract Arthropod trace fossils are described from the Borrowdale Volcanic Group, a sequence otherwise devoid of faunal evidence. Two forms, both made by the same probably myriapod-like organism, are assigned to the ichnogenera Diplichnites and Diplopodichnus. The lithologies preserving the trace fossils are non-marine and may have been deposited in a freshwater lacustrine environment; some of the traces were probably made in temporarily emergent conditions. The change from one form of trace to the other reflects drying out of the substrate. The trace fossils probably record some of the earliest freshwater arthropods, before the widespread colonization of land by the group.