The Siebel Dinosaur Complex in the Museum of the Rockies on the campus of Montana State University in Bozeman, Montana has displays dealing with the Tyrant Kings, commonly known as the T. rex (or, more formally, Tyrannosaurus rex) dinosaur. According to the display:
“Large top predators are extremely rare in their ecosystems. Tyrannosaurus was large, but not uncommon, and therefore was not likely a top predator. Its abundance suggests it was likely an opportunistic feeder, eating dead, sick, and weak prey similar to hyenas.”
With regard to the T-Rex diet, the displays showed:
T-Rex ate T-Rex
T-Rex ate Pachycephalosaurs
T-Rex ate Duck-Bills
T-Rex ate Triceratops
Shown above is a Triceratops pelvis bitten by a T-rex.