For example, theropod dinosaurs, notorious flesh-specialist predators (including Allosaurus, Carnotaurus, and the infamous Tyrannosaurus rex) had no obvious parallels to molars or premolars, no bladelike edges for shearing, no dome-shaped caps for crushing. Instead, all of their teeth were roughly similar in shape to canines. As a result, even though they did diverge in body size, allowing some partitioning of prey resources, theropod dinosaurs never diversified to fill the breadth of ecological roles seen in carnivorous mammals. In other words, there were no bone-cracking or saber-toothed theropods.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 90