Experimental Approaches in Neoichnology

A variety of experimental approaches have been taken in behavioral studies of mobile invertebrates, ranging from simple observations in aquaria to the use of sophisticated equipment. Studies involving these approaches are of greatest benefit to ichnology when destruction of primary sedimentary structures and formation of biogenic structures are also noted, but behavioral studies themselves are of practical value in reconstructing paleoethologies.

Invertebrates may be split into two artificial groups, according to their respective burrowing mechanisms. “Soft-bodied” animals rely on the generation of high internal-fluid pressures within specific body parts to produce anchors in the sediment. The musculature can then work against these anchors to pull the organism forward. “Hard-bodied” invertebrates rely on the action of appendages or spines to effect locomotion. The similarity of mechanisms within each group is due to limitations placed on the organism by the substrate in which it must move and by the required life functions of the animal itself.

In general, however, no such clear, parallel division is seen between sedimentary traces produced by members of the two groups. This disparity is due to the large variety of specific adaptations shown by these animals, and the somewhat greater independence of these individual adaptations from the sedimentary environment, relative to possible modes of locomotion. Herein lies the main justification for experimental neoichnology: to study these adaptations and their role in the formation of specific traces by specific organisms, thereby gaining information that is invaluable in interpretations of trace fossils.