Bioerosion trace in pseudo-coprolites from the Marília Formation (Upper Cretaceous of Paraná Basin), southeastern Brazil

HEITOR FRANCISCHINI; VOLTAIRE PAES NETO; AGUSTIN MARTINELLI; MARINA BENTO SOARES; CESAR SCHULTZ

Simposio; Tercer Simposio Latinoamericano de Icnología; 2015

Pseudo?coprolites are inorganic structures often confused with fossil faeces. The absence of some diagnostic features, such as inclusions, coprofabrics, grain adhesion, and defined shape, suffices to disregard these structures as coprolites. We revise the shapeless to rounded ?coprolites? from the Serra da Galga Member of the Marília Formation (Maastrichtian of Bauru Group, Paraná Basin), at ?Ponto 1 do Price? locality near the town of Peirópolis (Uberaba municipality, Minas Gerais State, Brazil), and conclude that they are, in fact, pseudo?coprolites related to calcretes. These data also agree with the geological setting of ?Ponto 1 do Price?, composed mainly of coarse sandstones and conglomerates, in which these pseudo?coprolites were found. In addition, some of these specimens exhibit superficial traces. These marks are distinct shallow ellipsoid borings with concave smooth flanks and acute to rounded ends. They form highly concentrated and randomly arranged clusters in the surface of some pseudo-coprolite samples. No filling, branching or spreiten are observed. These features are in accordance with the Asthenopodichnium Thenius, 1979 emended diagnosis, but the non-preferential orientation in the pseudo-coprolites and the lithic substrate allow us to propose a new ichnospecies. Bivalves are common in the invertebrate fossil record of Marília Formation and the group is the commonest bentic element of Late Cretaceous freshwater environments. Regarding these statements, we assume with caution, that a mussel is the best candidate to have produced the presented borings in calcrete clasts (?pseudo-coprolites?) of Upper Cretaceous fluvial systems of southeastern Brazil, interpreted as the oldest occurrence of a bioerosion trace possibly produced by bivalves in freshwater settings.