Protovirgularia dichotoma—Protovirgularia rugosa: An Example of a Compound Trace Fossil from the Lower Cretaceous (Agrio Formation) of the Neuquén Basin, Argentina

Abstract

This study focuses on the description of a compound trace fossil from the Cretaceous of the Neuquén Basin, Argentina. This structure comprises two discrete ichnotaxa: Protovirgularia cf. dichotoma M’Coy, 1850, and Protovirgularia cf. rugosa (Miller and Dyer, 1878). Open nomenclature is chosen due to some differences from the ichnospecies diagnoses. The compound trace as a whole is the product of locomotion and resting behaviors (repichnia and cubichnia); this is not questioned but discussed. The inferred producer is a deposit-feeding palaeotaxodont bivalve, which belongs to a taxonomic group almost unknown and not yet reported in the Neuquén Basin. The sample was taken from rocks interpreted as being deposited in a tide-influenced, marginal-marine setting, corresponding to the uppermost section of the Agrio Formation. This also represents one of the first cases of a compound trace fossil described for the Neuquén Basin.