Albertosaurus

Name:
Albertosaurus (Greek for "Alberta lizard"); pronounced al-BERT-oh-SORE-us
Habitat:
Forests of western North America
Historical Epoch:
Late Cretaceous (75 million years ago)
Size and Weight:
About 30 feet long and 3 tons
Diet:
Herbivorous dinosaurs
Distinguishing Characteristics:
Large head with numerous teeth; powerful hind legs; short arms
About Albertosaurus:

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" 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.

Scarily, paleontologists have found traces of evidence that Albertosaurus may have hunted in packs. If this is true, then it's likely that not even the armored, full-grown herbivores of Cretaceous North America (such as Triceratops) were truly safe from being turned into a quick lunch.