Size and Weight:
As carnivorous dinosaurs go, Albertosaurus is fairly well known, with multiple, more-or-less complete fossils of this famous tyrannosaur having been dug up in North America (many in the Canadian province of Alberta, after which the genus is named).
For all intents and purposes, Albertosaurus can be considered a slightly smaller version of Tyrannosaurus Rex, "only" weighing about three tons (compared to more than twice that for the largest T. Rex individuals) but every bit as dangerous. This tyrannosaur made its living by hunting the numerous herbivorous dinosaurs of the late Cretaceous period, probably making a specialty out of slow-witted hadrosaurs, or duck-billed dinosaurs.
Scarily, paleontologists have found traces of evidence that Albertosaurus may have hunted in packs. If this is true--and the conclusion is far from certain--then it's likely that not even the armored, full-grown herbivorous dinosaurs of late Cretaceous North America (such as Triceratops) were truly safe from being turned into a quick lunch.