Barnum Brown, mataimakin mai kula da Gidan Tarihi na Tarihi na Tarihi, ya sami kashi na farko na Tyrannosaurus rex a gabashin Wyoming a shekara ta 1900. Brown ya sami wani kashi na kashi a cikin Hell Creek Formation a Montana a shekara ta 1902, wanda ya kunshi kimanin kasusuwa 34 da aka samu. Rubuta a lokacin Brown ya ce "Quarry No. 1 ya ƙunshi femur, pubes, humerus, uku vertebrae da kasusuwa biyu da ba a bayyana ba na babban Dinosaur Dinosaur wanda Marsh bai bayyana ba... Ban taba ganin wani abu kamar haka daga Cretaceous ba". Henry Fairfield Osborn, shugaban Cibiyar Tarihi na Tarihi na Tarihi na Tarihi na Tarihi, ya kira Tyrannosaurus rex na biyu a 1905.
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