<P> Tyrannosaurus had very large olfactory bulbs and olfactory nerves relative to their brain size, the organs responsible for a heightened sense of smell . This suggests that the sense of smell was highly developed, and implies that tyrannosaurs could detect carcasses by scent alone across great distances . The sense of smell in tyrannosaurs may have been comparable to modern vultures, which use scent to track carcasses for scavenging . Research on the olfactory bulbs has shown that Tyrannosaurus rex had the most highly developed sense of smell of 21 sampled non-avian dinosaur species . </P> <P> Somewhat unusually among theropods, T. rex had a very long cochlea . The length of the cochlea is often related to hearing acuity, or at least the importance of hearing in behavior, implying that hearing was a particularly important sense to tyrannosaurs . Specifically, data suggests that Tyrannosaurus rex heard best in the low - frequency range, and that low - frequency sounds were an important part of tyrannosaur behavior . </P> <P> A study by Grant R. Hurlburt, Ryan C. Ridgely and Lawrence Witmer obtained estimates for Encephalization Quotients (EQs), based on reptiles and birds, as well as estimates for the ratio of cerebrum to brain mass . The study concluded that Tyrannosaurus had the relatively largest brain of all adult non-avian dinosaurs with the exception of certain small maniraptoriforms (Bambiraptor, Troodon and Ornithomimus). The study found that Tyrannosaurus's relative brain size was still within the range of modern reptiles, being at most 2 standard deviations above the mean of non-avian reptile EQs . The estimates for the ratio of cerebrum mass to brain mass would range from 47.5 to 49.53 percent . According to the study, this is more than the lowest estimates for extant birds (44.6 percent), but still close to the typical ratios of the smallest sexually mature alligators which range from 45.9--47.9 percent . </P> <P> A study in 2012 by Karl Bates and Peter Falkingham demonstrated that Tyrannosaurus had the most powerful bite of any terrestrial animal that has ever lived . They found that an adult Tyrannosaurus could have exerted 35,000 to 57,000 N (7,868 to 12,814 lbf) of force in the back teeth . Even higher estimates were made by professor Mason B. Meers of the University of Tampa in 2003 . In his study, Meers estimated a possible bite force of 183,000 to 235,000 N (41,140 to 52,830 lbf). A study in 2017 by Greg Erikson and Paul Gignac and published in the journal Scientific Reports found that Tyrannosaurus could exert bite forces of 8,526 N to 34,522 N (1,917 to 7,761 lbf) and tooth pressures of 718 to 2,974 MPa (104,137 to 431,342 psi). This allowed it to crush bones during repetitive biting and fully exploit the carcasses of large dinosaurs, giving it access to the mineral salts and marrow within bone that smaller carnivores could not access . Research done by Stephan Lautenschlager et al. from the University of Bristol, reveals Tyrannosaurus was also capable of a maximum jaw gape of around 80 degrees, a necessary adaptation for a wide range of jaw angles in order to power the creature's strong bite . </P>

When did tyrannasaurus rule as the apex predator