A NEW THEROPOD DINOSAUR LEK IN THE LATE CRETACEOUS (CENOMANIAN) DAKOTA SANDSTONE AT DINOSAUR RIDGE, COLORADO, USA

High-resolution aerial imagery captured via drone document 25 large scale, non-avian theropod mating display scrapes (Ostendichnus) along two stratigraphic levels of the Cretaceous (Albian-Cenomanian) Dakota Sandstone at Dinosaur Ridge, Colorado, USA. The newly identified scrapes allow the site to be designated as a fossilized nest display arena or lek, where a number of individuals congregated to perform courtship display rituals. We describe and identify trace morphologies, orientations, and patterns of clustering and overprinting. All scrapes are composed of the diagnostic bilobate or bowl-shaped expressions of Ostendichnus and Ostendichnus-like traces and contain well-detectable toe claw marks. A new means to determine the direction the trace maker faced while creating the scrapes is proposed for Ostendichnus lacking a pile of excavated sediment at the posterior. Analysis of the Dinosaur Ridge lek and of 3 previously known leks in Western Colorado—Club Gulch (n = 2) and Roubideau Creek— allow insight into the social behavior of the trace making dinosaurs by comparing their distribution patterns to those observed in modern lekking analogs (birds).