Vertebrate and Invertebrate Trace Fossils in the Late Pennsylvanian (Carboniferous) Fluvio-Lacustrine San Giorgio Basin (South-West Sardinia): Remarks on the Oldest Continental Ichnoassociation of Italy

ABSTRACT

A new study of the ichnotaxonomy and palaeoecology of the Late Pennsylvanian San Giorgio Basin's trace fossils was carried out. The tetrapod tracks were attributed to Batrachichnus salamandroides and to indet. tracks with a possible small temnospondyl and/or lepospondyl affinity. The invertebrate trace fossils include locomotion traces (Diplichnites isp.), grazing traces (Cochlichnus anguineus), and feeding structures (Treptichnus bifurcus, Treptichnus isp.). The trace fossils were evaluated by means of ichnofacies, highlighting a transitional Scoyenia-Mermia ichnofacies, typical of Carboniferous freshwater settings. The trace fossil co-occurrence and taphonomy was utilized to give a new interpretation of the fossil-bearing lithofacies, which are dolomitic mudstones-fine sandstones expression of marginal lacustrine environments repeatedly subject to flooding (three different ichnoassociations highlight different bathymetry/emersion). This is the oldest continental ichnoassociation of Italy, and its moderately high diversity and complexity suggest further study of this important Carboniferous trace fossil locality.

KEYWORDS:

• Pennsylvanian
• Tetrapod tracks
• Invertebrate trace fossils
• Continental ichnofacies

Acknowledgments

We would like to thank U. Nicosia, M. A. Conti, E. Sacchi, and S. Piras for the invaluable help in the first phases of research and for the useful discussion and advices. We thank also Spencer G. Lucas and Sebastian Voigt for reviewing the manuscript.

Funding

We gratefully acknowledge the Sardinia Region Government for the financial support of the Ph.D. scholarship (P.O.R. Sardegna F.S.E. Operational Program of the Autonomous Region of Sardinia, European Social Fund 2007–2013–Axis IV Human Resources, Objective l.3, Line of Activity l.3.1) and the Cagliari University CAR Project G.L. Pillola “Paleobiodiversità: strumento di base in biostratigrafia, in paleoecologia e nella valorizzazione dei beni culturali Geo-Paleontologici.”