Analysis of Asteriacites von Schlotheim 1820 from Mulichinco Formation (Lower Cretaceous, Neuquén Basin) and ichnotaxonomic implications

The last review of Asteriacites (Knaust and Neumann 2016) dismissed sculpture as an ichnotaxobase for this ichnogenus and used simple morphometric parameters to differentiate the ichnospecies, reducing them to three: A. lumbricalis, A. stelliformis, and A. quinquefolius. In this work, ichnotaxonomic tools are discussed through the analysis of trace fossils assigned to this ichnogenus from the Mulichinco Formation (Valanginian) of the Neuquén Basin, northern Patagonia. New Asteriacites-bearing levels from different localities are described, and specimens that were previously assigned to A. lumbricalis are reassigned to A. stelliformis. Taking into account this material and previous works where Asteriacites were analysed, we observed that some problems arise in the ichnospecific assignment when applying the methodology of Knaust and Neumann (2016).  Therefore, in this work, three simple criteria were incorporated to facilitate the ichnospecific assignment through this morphometric approach. It is also noted that the specimens with epirelief preservation are challenging to identify because the delineation of the edge of the trace, necessary for the morphometric analysis, depends on the used methodology. Additionally, examples of previous works are analysed, allowing discussion of proposed ichnospecific ichnotaxobases and the relevance of sculpture.