Sometimes They Come Back: Recovery and Reinterpretation of a Trackway Slab from the Permian Coconino Sandstone of the Southwestern United States

Abstract

When a fossil vanishes to a private collection, it must be considered lost to science because, frequently, it is no longer available for study. Fortunately some fossils occasionally are regained. We had the opportunity to recoup an interesting footprint-bearing slab that was part of a private collection in Italy. The specimen, found in 1992 near Seligman, Arizona (USA) was described, before disappearing, as one of the best fossil examples of vertebrate (Chelichnus [Laoporus])-on-invertebrate (Octopodichnus) predation. After a careful re-examination of the slab, the primary conclusions of the former describers are demonstrably groundless. The reanalysis of the tracks, as well as peculiar sedimentary structures associated with the tracks, allowed obtaining new information about the depositional environment and the complex interactions between the type of substrate and trackmaker behavior. The re-examination of the specimen also revealed interesting aspects about trackmaker biomechanics.

Keywords:

• Tetrapod tracks
• Invertebrate tracks
• Chelichnus
• Permian
• Coconino Sandstone
• Biomechanics

ACKNOWLEDGMENTS

We thank the Land authorities on Cultural Heritage (Soprintendenza Archeologica per le Marche) that allowed the study of the specimen. A special acknowledgement is due to our colleague S. Ciccacci (University of Rome), specialist of desert geomorphology, for the interesting discussion. The Community and the Mayor of Serrapetrona and the carabineers of the Nucleo Tutela Patrimonio Culturale di Ancona selflessly helped us during the study. Mostly, we are indebted to James Farlow (Indiana–Purdue University Fort Wayne, USA) for his enlightening and priceless comments and suggestions. Any errors in the text must be attributed solely to the authors.