Bioerosion traces in bones reveal an increase in ethological diversity in the insect exploitation of carcasses in the late Triassic

This study presents the first detailed description of bioerosion traces produced by insects in bones from the Santa Cruz Sequence (early Carnian, Santa Maria Supersequence, Brazil). An array of traces is reported, consisting of notches, a tube, trails of grooves attributed to the ichnotaxon Osteocallis mandibulus and ornamented depressions attributed to a new ichnotaxon Osteograptus thanatobios igen. nov. et isp. nov. The traces were likely produced by insects, but a less inclusive taxonomic attribution is currently not possible. The ethological interpretation for the bioerosion structures is that they represent feeding traces. This report increases the contrast between the Middle and Late Triassic bioerosion record, since the latter is significantly more diverse and abundant. Hypotheses related to the onset of the Carnian Humid Episode as well as taphonomic biases are discussed as possible explanations for this contrast.