Paleoecology of circular perforations in bone: a study case in glyptodont carapaces

PIRRONE, CECILIA A.; LUNA, CARLOS ALBERTO

Colonia del Sacramento

Simposio; III Simposio Latinoamericano de Icnología; 2015

Bioerosion occurs in all kind of hard substrate, both biogenic and non-biogenic. However, a few bioerosion structures are restricted to skeletons of living organisms. They reflect ecological interactions between the host and the tracemaker. This kind of bioerosion traces on fossil tetrapod bones isinterpreted as novel evidence of ecological relationships between mammals and arthropods, in a continental setting. The studied vertebrate remains correspond to a faunal association dated as late Pleistocene ? early Holocene from outcrops surrounding the Mar Chiquita lake, at Córdoba province, central Argentina. Although bioerosion trace fossils in bones have been reported worldwide as evidence of paleoecological interactions, there is no detailed study developed in Argentina for this faunal association. Considering trace fossils as a result of a combination of substrate, tracemaker, and behavior; we analyzed a particular morphology of bioerosion traces in bone: circular perforations usually interpreted as pupichnia ethology, and we compare them with similar extant examples of morphology and substrate (bone tissue). The general morphology, internal shape, and location of circular (~15mm in diameter) perforations, placed in external bone surface of glyptodont carapaces, arecomparable with similar structures observed in extant armadillo carapaces, produced by invertebrates ectoparasites. So, restricting two parameters (substrate and behaviour), we analyzed the third one (tracemaker) under the light of actualism. As result, we propose a preliminary interpretation of shallow, circular perforations on external bone surface of glyptodont carapaces as reflecting parasitism. Evidence of a possible re-ossification process, on the outer margin of perforations, supports the proposed ethological interpretation. These trace fossils are the first record of this kind of ecologicalinteraction in continental ecosystems during the late Pleistocene of Argentina. As conclusion, the analysis of bioerosion traces on bones is proposed as a methodological tool to help understanding trophic relationships and structure of food webs in past ecosystems.