A NEW, PARASITOID INSECT (CF. DIPTERA: PIPUNCULIDAE) OCCURRING WITH MULTIPLE TIPULIDS (CRANE-FLIES) IN A SINGLE PIECE OF AMBER FROM THE HELL CREEK FORMATION (LATEST-MAASTRICHTIAN)

Insects, among the most diverse macroscopic organisms, are key components in virtually every living terrestrial ecosystem, and provide nuanced paleoenvironmental information not afforded by sole focus on vertebrate communities. A unique and impactful subset, the parasitoids, afflict and parasitize a wide variety of hosts. Amber has historically provided the most precise and effective means of studying prehistoric insect taxa, because of its high preservation potential, however amber with observable inclusions is scarce in many geologic formations, and not evenly distributed through time. This is especially apparent in the late Maastrichtian Hell Creek Formation, which, after 100+ years of scientific research, yielded no amber insects until first reported in 2010¹. This prior deficiency had perpetuated a biased reconstruction of the Hell Creek ecology, which lacked the key insect component. Carrol², using the methods of DePalma et al.¹, successfully recovered a second ensemble of amber insects. Regrettably, however, peer-reviewed Hell Creek insect research has not progressed beyond the preliminary report from 2010. Here, we add to the known diversity of the Hell Creek insect fauna by reporting a new, parasitoid, member of the Diptera. The new insect compares favorably with the Pipunculidae, a Family hitherto known only as early as the Eocene, although molecular data suggests diversification in the Maastrichtian. Interestingly, the Hell Creek specimen was found in a block of amber containing multiple crane flies (Tipulidae), the exclusive host of the extant pipunculid Nephrocerus. The fossil association could support that the earliest Pipunculidae had a similar affinity for Tipulidae, helping to resolve the early ecology of the clade. Of greatest significance, the new amber insects are important in resolving the complexity of the hitherto-unknown Hell Creek insect fauna, and its integration with the rest of the contemporaneous ecology, immediately preceding the KPg extinction.

¹ DePalma, R., F. Cichocki, M. Dierick, and R. Feeney. 2010. Preliminary notes on the first recorded amber insects from the Hell Creek Formation. The Journal of Paleontological Sciences. JPS.C.10.0001.

²Carrol, N., 2016, Hell Creek amber: a new fossil archive prior to the K-Pg boundary, GSA Abstracts with programs 48(7)