2nd Place: Hymenoptera from a new Canadian amber deposit close to the Cretaceous-Paleogene extinction

Questions remain regarding the evolutionary and ecological history of insects, in part due to their low potential for fossilization. There is a 17-million-year gap in the insect fossil record surrounding the Cretaceous-Paleogene (K-Pg) mass extinction (66 Ma), a catastrophe that shaped the subsequent evolution of modern biotic communities. The rarity of insect fossils near the K-Pg mass extinction limits our understanding of how insect lineages were impacted by this event. We used synchrotron X-ray micro-CT scans to examine the Hymenoptera fauna captured in a newly discovered amber deposit in the Big Muddy Badlands of Saskatchewan, dated to the latest Cretaceous (67.04 ± 0.16 Ma). Due to the fragility of Saskatchewan amber, synchrotron imaging is a valuable tool for developing detailed descriptions of insects and determining their evolutionary relationship to extant taxa. Of the 47 arthropod inclusions found in Big Muddy amber so far, thirteen are hymenopterans and represent at least five families of small parasitoid wasps and ants (Platygastridae, Scelionidae, Rotoitidae, Mymaridae, and Formicidae). The presence of two ants within the first 47 inclusions from Big Muddy amber is anomalous when compared to other Cretaceous amber deposits in North America, which are depauperate of ants. This faunal difference may be linked to specific habitat represented by Big Muddy amber, or it may reflect the growing abundance of formicids in the Late Cretaceous ecosystems of western North America. Big Muddy amber fills a critical faunal gap and furthers our understanding of the insect lineages that have come to dominate modern ecosystems.