Simulated weathering of dinosaur tracks and the implications for their characterization

Abstract

Digital models of the tracks of bipedal theropod and ornithopod dinosaurs, and the quadrupedal tracks of a sauropod, were computationally eroded to investigate the effects of erosion on the shapes, sizes, and diagnostic details of fossil tracks. Narrow and (or) angular details, such as claw marks, interdigital ridges, and internal ridges, are removed early in erosion, creating the potential for misidentification of eroded theropod tracks as those of ornithopods. However, with the erosion models presented here, all tracks retain their basic shapes as indicated by the relative constancy of their interdigital angles and by the relative constancy of their footlength:footwidth ratios. Surface lengths of tracks did not increase significantly with erosion, so that dinosaurian hip height and speed estimates derived from trackways would not be greatly in error if based on eroded surface tracks. Synthetic undertracks from the surface tracks were also produced using information from published physical models of track formation. The differences between a weathered surface track and a freshly exposed, simulated undertrack are sufficient so that the two model tracks would not be confused. Large, rounded tracks are much better at retaining their characteristics than small, angular tracks, with the implication that large tracks may be over-represented in the fossil record, but they may be more reliably attributed to the appropriate trackmaker. This would bias estimates of dinosaur taxonomic diversity and body size ranges based on trackway evidence.