Bioerosive ichnofossils in the holotype of Trachycalyptoides achirense (Glyptodontidae, Cingulata) from the Late Miocene Altiplano of Bolivia

Abstract

The Late Miocene locality of Achiri from the Bolivian Altiplano preserves a diverse mammalian fauna, of which the glyptodontids are represented by Trachycalyptoides achirense. Glyptodontids and other cingulates are valuable for palaeoecological analyses because their dermal armour provides an excellent substrate for the preservation of ichnofossils recording biotic interactions. We assessed the dermal armour of the holotype of Trachycalyptoides achirense, consisting of a caudal tube and various fragments of dorsal carapace, for evidence of trace fossils and identified the first evidence of both parasitism and faunivory for the Achiri fauna. Both the caudal and carapace armour preserves evidence of round holes that are variable in morphology but similar to those observed in fossil cingulates and modern armadillos and which have been linked to the action of fleas related to the modern hectopsyllid taxon Tunga perforans. These holes are assigned to the ichnotaxon Karethraichnus, expanding the record of this trace to the Late Miocene of Bolivia. Bite marks and linear grooves on the caudal armour preserve evidence of the consumption of meat, but are not severe enough to be considered evidence of predation. Instead, the most likely explanation is that they were emplaced during scavenging by the only known faunivore from Achiri, Borhyaenidium altiplanicus. The continued expansion of the trace fossil record associated with fossil cingulates will eventually allow for the potential of testing hypotheses based on modern parasites, including the relevance of predation pressure, resource availability and environmental variables (including precipitation and altitude) to parasite abundance and diversity.