Pie chart of the time averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area (sampled near Fort Peck Reservoir in northeastern Montana). "Triceratops" is the most common dinosaur at 40% (n = 72); Tyrannosaurus is second at 24% (n = 44); "Edmontosaurus" is third at 20% (n = 36) followed by "Thescelosaurus" at 8% (n = 15), "Ornithomimus" at 5% (n = 9), and "Pachycephalosaurus" and "Ankylosaurus" at 1% (n = 2).