Size-driven preservational and macroecological biases in the latest Maastrichtian terrestrial vertebrate assemblages of North America

The end-Cretaceous (K/Pg) mass-extinction event is the most recent and well-understood of the “Big Five” and triggered establishment of modern terrestrial ecosystem structure. Despite the depth of research into this event, our knowledge of upper Maastrichtian terrestrial deposits globally relies primarily on assemblage-level data limited to a few well-sampled formations in North America, the Hell Creek and Lance formations. These assemblages disproportionally affect our interpretations of this important interval. Multiple investigations have quantified diversity patterns within these assemblages, but the potential effect of formation-level size-dependent taphonomic biases and their implications on extinction dynamics remains unexplored. Here, the relationship between taphonomy and body size of the Hell Creek and Lance formation dinosaurs and mammals are quantitatively analyzed. Small-bodied dinosaur taxa (< 70 kg) are consistently less complete, unlikely to be articulated, and delaye...