Phys.org has a story about tyrannosaurs… seems they didn’t share much.  A new study published in the Canadian Journal of Earth Sciences found that tyrannosaur juveniles out competed medium sized carnivores wherever their adults rose to dominance.  

The research conducted by Thomas Holtz, a principal lecturer in the University of Maryland’s Department of Geology, verified previous anecdotal reports of a dramatic drop-off in diversity of medium-sized predator species in communities dominated by tyrannosaurs. Diversity of prey species, on the other hand, did not decline. This suggests that medium-sized predators did not disappear because of a drop off in their prey, and that something else—likely young tyrannosaurs—stepped in to fill their ecological role. The study was published online on June 17, 2021, in the Canadian Journal of Earth Sciences.

“Earlier in the history of dinosaurs, in most communities you’d have a bunch of different types of carnivores of various size ranges from small fox-sized all the way up to the occasional giants,” Holtz said. “Then something happens between 95 and 80 million years ago, where we see a shift. The really big carnivores, larger than an elephant, like tyrannosaurs and their kin, become the apex predators, and the middle-sized predators, say leopard to buffalo-sized carnivores, are either missing or very rare.”