Brown chọtara ọkpụkpụ ọzọ na Hell Creek Formation na Montana na 1902, gụnyere ihe dị ka ọkpụkpụ 34 fosili. N'ide n'oge ahụ Brown kwuru "Quarry No. 1 nwere femur, pubes, humerus, vertebrae atọ na ọkpụkpụ abụọ a na-amaghị ama nke nnukwu Dinosaur Carnivorous nke Marsh akọwaghị.... Ahụtụbeghị m ihe ọ bụla dị ka ya site na Cretaceous". Henry Fairfield Osborn, onye isi oche nke American Museum of Natural History, kpọrọ aha nke abụọ Tyrannosaurus rex na 1905.
eze