Zoophycos: strip mine, refuse dump, cache or sewage farm?

In recent papers, Kotake (1989. 1991) has demonstrated that the material that comprises the spreite lamina of Zoophycos derives from a higher level, presumably at or near the sea floor. And because this material was emplaced as pellets, assumed to be of faecal origin. The Zoophycos animal is considered to have fed on detritus at the sea floor and to have deposited its excreta deeply beneath it. Ekdale and Bromley (1983) had previously shown that in both Zoophycos and Chondrites, sediment is piped down from higher levels, but they did not reach the logical trophic conclusions that Kotake (1991) has done: that the Zoophycos animal is a detritus feeder. As Kotake has pointed out, his new model opposes previous interpretations of Zoophycos activity, which are basically those of Seilacher (1967) and Simpson (1970). These authors envisaged the spreite as representing a deposit-feeding, strip-mining activity where sediment exploitation and waste disposal occurred almost simultaneously. This is a particularly low-cost exercise in which there is minimal transport of sediment. Indeed, on this basis, the Zoophycos animal has been interpreted as having both mouth and anus at the same end of the body, suggesting a sipunculan worm (Wetzel & Werner 1981). Donaldson and Simpson (1962) considered mounds, Chomatichnus, associated with Zoophycos to represent faecal accumulations on the sea floor, thereby implying upward conveyor activity. But large-scale downward conveyance has now been demonstrated, and the elegant strip mine model no longer adequately accounts for the structure of Zoophycos. Yet many features of the spreite lamina nevertheless meet the strip mine paradigm; and why should excrement be deposited in such a costly manner? Is Zoophycos just a beautiful cesspit.