Daspletosaurus was a genus of large, bipedal carnivorous dinosaurs belonging to the family Tyrannosauridae. The name, meaning “frightful lizard,” aptly describes this powerful predator that lived in ancient western North America. Fossil evidence allows paleontologists to pinpoint the precise range and time period this imposing carnivore inhabited.
Geographic Home: Laramidia
The geographic range of Daspletosaurus was restricted entirely to Laramidia, the western landmass of North America during the Late Cretaceous. Laramidia was separated from the eastern landmass, Appalachia, by the vast Western Interior Seaway. The known fossil distribution of Daspletosaurus spans modern-day Alberta, Canada, and Montana, United States.
Various species of this genus are found across distinct geological formations within this region. For example, the type species, Daspletosaurus torosus, is known from the Oldman Formation in Alberta, and Daspletosaurus horneri was discovered in the Two Medicine Formation in Montana. These discoveries confirm the genus was a top predator across the northern stretch of Laramidia, occupying the coastal plains that bordered the seaway.
The Late Cretaceous Timeline
Daspletosaurus lived during the Late Cretaceous Period, specifically within the middle to late Campanian stage. Its known temporal range falls approximately between 79 and 74 million years ago. This placement puts it chronologically between earlier tyrannosaurids and its famous, much younger relative, Tyrannosaurus rex.
Fossil evidence shows that different species appeared at slightly different times throughout this stage. For instance, the earliest specimens, like D. torosus, date to around 77 million years ago, while D. horneri is found in slightly younger deposits. This staggered appearance suggests the species may represent a direct evolutionary line, or anagenesis, over this period, before the genus disappeared around 74 million years ago.
The Environment of Daspletosaurus
The habitat of Daspletosaurus was a lush, subtropical environment characterized by a warm and humid climate. This region consisted of vast coastal plains and low-lying areas situated between the rising proto-Rocky Mountains and the Western Interior Seaway. Numerous rivers and streams flowed down from the mountains, creating extensive floodplains, swamps, and forested areas.
The geological formations where most fossils are found, such as the Dinosaur Park and Two Medicine Formations, represent these ancient terrestrial deposits. This rich and diverse ecosystem, including large herbivorous dinosaurs like hadrosaurs and ceratopsians, provided a steady food source for the carnivore.