Question: when did tyrannosaurus rex rule as apex predator

title: Tyrannosaurus
text: Tyrannosaurs had large olfactory bulbs and olfactory nerves ( relative to their brain size ) . These suggest a highly developed sense of smell which could sniff out carcasses over great distances , as modern vultures do . Research on the olfactory bulbs of dinosaurs has shown that Tyrannosaurus had the most highly developed sense of smell of 21 sampled dinosaurs . Opponents of the pure scavenger hypothesis have used the example of vultures in the opposite way , arguing that the scavenger hypothesis is implausible because the only modern pure scavengers are large gliding birds , which use their keen senses and energy - efficient gliding to cover vast areas economically . Researchers from Glasgow concluded that an ecosystem as productive as the current Serengeti would provide sufficient carrion for a large theropod scavenger , although the theropod might have had to be cold - blooded in order to get more calories from carrion than it spent on foraging ( see Metabolism of dinosaurs ) . They also suggested that modern ecosystems like the Serengeti have no large terrestrial scavengers because gliding birds now do the job much more efficiently , while large theropods did not face competition for the scavenger ecological niche from gliding birds .