Abstract

Graphoglyptids are a group of deep-sea trace fossils that exhibit ornate burrow geometries. Feeding patterns represented by these burrows have been interpreted as fodinichnial (mining), pascichnial (grazing), and/or agrichnial (farming). In this study, several different graphoglyptid trace fossils were analyzed quantitatively using fractal analysis to determine which of these three feeding modes is most appropriate as an interpretation. Graphoglyptid burrows lend themselves to fractal geometric analysis, because they commonly exhibit the essential fractal characteristics of scale invariance and self similarity. Fractal analysis is presented as a tool for analyzing geometric configurations by combining shape complexity and space usage into one number, the fractal dimension. Fractal dimensions of such graphoglyptid burrows as Paleodictyon and Spirorhaphe were compared with those of known fodinichnial burrows, such as Zoophycos, and pascichnial trails, such as Scolicia, all from Zumaia, Spain. Results indicate that the deposit-feeding burrows (fodinichnia and pascichnia) illustrate a high fractal dimension, as would be expected for a deposit-feeding–optimal foraging strategy. Graphoglyptids illustrate a consistently lower fractal dimension than the deposit-feeding burrows, thus providing evidence against the suggestion that they represent fodinichnial or pascichnial behaviors. This observation supports the hypothesis that graphoglyptids represent agrichnial activity rather than mining or grazing activities.

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