Abstract
An exceptionally well-preserved example of Phymatoderma granulatum from continental slope deposits within the Pliocene Upper Onzole Formation, coastal Ecuador, supports an important reinterpretation of this large, branching, subhorizontal burrow system. Traces such as this have been regarded simply as fodinichnia (the work of subsurface deposit feeders). However, we propose that the trace producer was capable of changing its feeding strategy as a probable adaptation to a variable trophic regime. Tunnels within the burrow system are filled with pelleted volcanic ash conveyed from the seafloor to subsurface storage areas, indicating surface deposit feeding ; the same tunnels enclose secondary tunnels that rework the primary fill of pellets, pointing to recycling/restocking of fecal banks as another trophic behavior. Alternative feeding strategies represented in P. granulatum could be the reactions of the burrowing animal to a pulsed delivery of labile organic material at the ocean bottom (in this instance associated with large ashfalls).
