Kotake, Nobuhiro 1989 07 15: Paleoecology of the Zoophycos producers. Lethaia, Vol. 22. pp. 327–341. Oslo. ISSN 0024–1164. Well‐preserved Zoophycos and Spirophyton‐like burrows occur in the Upper Pliocene deep‐sea sediments exposed along the southern coast of Boso Peninsula, central Japan. They consist of an axial tunnel and helically coiled spreite with fecal pellets. In most cases the two kinds of trace fossil are found separately. In several complete specimens, however, the upper and lower portions represent a Spirophyton‐like burrow and Zoophycos, respectively. The downward increase in size of the spreite and fecal pellets in a single burrow suggests that the complete Zoophycos was built successively as the producing animal grew. The occurrence of incomplete Zoophycos may have resulted from post‐mortem destruction by echinoid locomotion and turbidity currents. In some cases, the uppermost portion of the axial tunnel is covered with a thin tuff layer. Fecal pellets in such burrows consist of the same tuffaceous material which must have originated from the overlying tuff layer. This fact indicates that the burrow producer did not feed on organic matter within the sediments but foraged detritus on the sea floor. The animal could probably stretch a part of the body from the top of the axial tunnel for feeding and systematically pack the fecal pellets into the sediments. Such segregation between the feeding place and the excretory space is interpreted as an efficient feeding strategy for the detritus‐feeding burrowers in the deep sea. D Zoophycos, Spirophyton‐like burrow, paleoecology, feeding and excretory behavior, Boso Peninsula, Japan.

The feeding mechanism of Zoophycos producers demonstrates non‐selection by particle size or quality. The characteristic morphology and mode of Occurrence of Zoophycos and the presence of pellets with pyroclastic grains imply that the Zoophycos producers were surface deposit‐feeders. They dwelt in a burrow within the sediment and ingested the grains with nutrient detritus on the sea floor around the burrow opening. Fecal pellets containing pyroclastic grains were compared with the overlying volcanic ash layers through the analyses of grain size and mineral composition based on samples from two horizons in the Upper Pliocene of Boso Peninsula, central Japan. Judging from the comparative analyses, no significant differences were found between the ash layer and the fecal pellets. This fact strongly suggests that the Zoophycos producers appear to indiscriminately ingest particles on the sediment surface. Environments of low nutrition input such as the deep sea, non‐particle size and quality selection in Zoophycos producers may be the feeding strategy for the detritus‐feeding burrow‐dwellers. □ Zoophycos, surface deposit‐feeding, Pliocene Shiramazu Formation, Boso peninsula, Japan.

Kotake, N. 1992 07 15: Deep‐sea echiurans: possible producers of Zoophycos. The trace fossil Zoophycos in the upper Pliocene deep‐sea deposits (Shiramazu Formation) distributed in the southernmost part of Boso Peninsula, central Japan, appears to be a product of feeding and excretory behavior by surface deposit‐feeders inhabiting middle bathyal depths. Ecology and anatomy of modern deep‐sea echiurans are consistent with those of the Zoophycos producers based on the Pliocene examples. Consequently, deep‐sea echiurans may be producers of Zoophycos. Systematic lamellae structures of the spreite reflect excretory behavior in sediment resulting from deposit‐feeding on the sea‐floor. Zoophycos, deep‐sea echiurans, Pliocene, Boso Peninsula, Japan.