Composite ichnological-pathological evidence for arthropod parasitism on osteoderms of Boreostemma acostae (Glyptodontidae, Cingulata) from La Venta, Colombia

The first evidence of parasite-induced bioerosion is reported from large cingulates from the Middle Miocene La Venta fauna of Colombia. These traces occur primarily on osteoderms in the anterior caudal armor of the moderate-sized glyptodontine Boreostemma acostae. The traces are small (~3–3.5 mm wide), cylindrical, non- penetrative holes (~4.5 mm deep) on the external surface of osteoderms that most commonly occur at epidermal sulci or at triple junctions between three osteo- derms. These traces are most morphologically similar to the ichnotaxon Karethraichnus kulindros; however, forms similar to K. zaratan and K. minimum also occur. Dense bone on the hole margins indicates that these features comprise compound trace fossils and pathologies. It is postulated that these traces were emplaced by fleas similar to the modern malacopsyllid flea taxon, Tunga perforans which emplace similar, but not identical holes, in modern armadillo osteoderms. The La Venta traces extend the range of purported hectopsyllid flea traces to the Middle Miocene of Colombia. To date, traces attributable to hectopsyllid fleas have been observed on Oligocene to Pleistocene/Early Holocene glyptodontids and Late Miocene to present-day armadillos. The La Venta Boreostemma traces support the hypothesis that the tick-cingulate relationship was initiated on glyptodontids, subsequently moving to armadillos later in the Neogene.