Behavioural impacts on the taphonomy of dragonflies and damselflies (Odonata) from the Lower Cretaceous Crato Formation, Brazil

The relative completeness of Odonata (dragonflies and damselflies) fossils from the Crato Formation is investigated and compared to other fossil insect groups from the same formation. Tagma completeness is measured as present, partial, or absent, with some additional subdivision of body components (head, thorax, limbs, individual wings, anterior and posterior abdomen). These data are statistically explored for trends using principal coordinate analysis. While no definitive clustering is identified, most Crato Formation Odonata fossils plot positively on coordinate two, whereas the majority of non-odonatan insect fossils plot negatively on this coordinate. This shows that the Crato Formation odonates are less complete compared to other insect groups from the same beds. Specimens preserved as isolated wings and those preserved with damaged or lost abdomens are identified as contributing to this difference. The causes of these differences are discussed, highlighting collection bias, predation, carcass scavenging, physical conditions of the palaeoenvironment, as well as the autecology of odonates.