Science, Tech, Math › Animals & Nature Daspletosaurus Share Flipboard Email Print Daspletosaurus (Wikimedia Commons). Animals & Nature Dinosaurs Carnivores Basics Paleontologists Dinosaurs & Birds Herbivores Marine Reptiles Prehistoric Mammals Amphibians Birds Habitat Profiles Mammals Reptiles Wildlife Conservation Insects Marine Life Forestry Evolution View More By Bob Strauss Science Writer B.S., Cornell University Bob Strauss is a science writer and the author of several books, including "The Big Book of What, How and Why" and "A Field Guide to the Dinosaurs of North America." our editorial process Bob Strauss Updated March 17, 2017 Name: Daspletosaurus (Greek for "frightful lizard"); pronounced dah-SPLEE-toe-SORE-us Habitat: Swamps of North America Historical Period: Late Cretaceous (75-70 million years ago) Size and Weight: About 30 feet long and three tons Diet: Herbivorous dinosaurs Distinguishing Characteristics: Massive head with numerous teeth; stunted arms About Daspletosaurus Daspletosaurus is one of those dinosaur names that sounds better in English translation than in the original Greek--"frightening lizard" is both scarier and more pronounceable! Other than its position near the top of the late Cretaceous food chain, there's not much to say about this tyrannosaur: like its close relative, Tyrannosaurus Rex, Daspletosaurus combined a massive head, a muscular body, and many, many sharp, pointy teeth with a ravenous appetite and puny, comical-looking arms. It's likely that this genus included a number of similar-looking species, not all of which have been discovered and/or described. Daspletosaurus has a complicated taxonomic history. When the type fossil of this dinosaur was discovered in Canada's Alberta Province in 1921, it was assigned as a species of another tyrannosaur genus, Gorgosaurus. There it languished for almost 50 years, until another paleontologist took a closer look and promoted Daspletosaurus to genus status. A few decades later, a second putative Daspletosaurus specimen wound up being assigned to yet a third tyrannosaur genus, Albertosaurus. And while all this was going on, the maverick fossil-hunter Jack Horner suggested that a third Daspletosaurus fossil was actually a "transitional form" between Daspletosaurus and T. Rex! Dale Russell, the paleontologist who assigned Daspletosaurus to its own genus, had an interesting theory: he proposed that this dinosaur coexisted with Gorgosaurus in the plains and woodlands of late Cretaceous North America, Gorgosaurus preying on duck-billed dinosaurs and Daspletosaurus preying on ceratopsians, or horned, frilled dinosaurs. Unfortunately, it now seems that the territory of these two tyrannosaurs did not overlap to the extent Russell believed, Gorgosaurus being largely restricted to northern regions and Daspletosaurus inhabiting southern regions.