PALAXIUS CHOSMALALENSIS N. ISP., A NEW CRUSTACEAN MICROCOPROLITE FROM THE LOWER CRETACEOUS OF ARGENTINA AND NEW CRITERIA FOR THE CLASSIFICATION OF ICHNOSPECIES OF PALAXIUS

Crustacean microcoprolites are abundant constituents in the Upper Jurassic–Lower Cretaceous of the Neuquén Basin (Argentina). A new record of these particles is described from the lowermost Olcostephanus (O.) atherstoni ammonite Zone (lower Valanginian) in the Mulichinco Formation at Puerta Curaco section, north of the Neuquén province. Coprolites come from shallow-water oyster-dominated biostromes and belong to a new ichnospecies, Palaxius chosmalalensis n. isp., which was previously described as P. decemlunulatus (Paréjas) from the Upper Cretaceous of Egypt. As a consequence of the description of the new ichnospecies, we propose to incorporate quantitative criteria regarding the angle with which the canals are oriented, as well as its position with respect to the center of symmetry of the coprolite.