Evolution of Terrestrial Burrowing Invertebrates

INTRODUCTION The important role of fauna in modifying the regolith by redistributing particles is now widely acknowledged (e.g., Paton et al. 1995). One issue of some importance to regolith studies and the interpretation of paleosols is how the role of terrestrial bioturbation has evolved since life first invaded the land areas of Earth in the Early Paleozoic. This particular issue was raised during a discussion session at an earlier regolith conference (Eggleton 1998) and this paper is an attempt to answer this more fully in respect to invertebrates. In particular this contribution attempts to address the issue of when different kinds of burrowing invertebrates, in which burrowing is demonstrated or may be reasonably assumed, first appeared. In an ideal situation a combination of hard evidence provided by well dated fossils and trace fossils together with less certain but nevertheless important information obtained from habitat reconstruction and phylogenetic relationhips would be employed. However, such a combination is rarely achieved and hence most of the relationships discussed are based on a mixture of available evidence.