Gorgosaurus was a large, predatory dinosaur, a member of the tyrannosaurid family that included the later and larger Tyrannosaurus rex. Its name, meaning “fierce lizard,” reflects its position as an apex predator. The fossil record of Gorgosaurus is exceptionally rich, with over 20 skeletons recovered, making it one of the best-represented tyrannosaurids known to science. These well-preserved remains offer a detailed window into the life and ancient world of this formidable carnivore.
The Cretaceous Timeframe
The existence of Gorgosaurus is fixed within the Late Cretaceous period, specifically during the Campanian stage, approximately 76.6 to 75.1 million years ago. This interval occurred late in the “Age of Dinosaurs,” preceding the major extinction event that ended the Cretaceous period. The Campanian was a time of significant dinosaur diversity, especially in North America, which was then experiencing a global cooling trend.
Although the global climate was generally warm during the Cretaceous, the Campanian included a progressive cooling phase driven by falling atmospheric carbon dioxide levels. This period saw the flourishing of many large herbivorous dinosaurs, such as ceratopsids and hadrosaurs, which provided the primary prey base for predators like Gorgosaurus.
Fossil Evidence and Discovery Sites
The geographic range of Gorgosaurus is defined by the locations where its fossil remains have been unearthed in western North America, spanning modern Canada and the United States. The most prolific site is the Dinosaur Park Formation in Alberta, Canada, which has yielded dozens of specimens, including the nearly complete holotype skeleton discovered in 1913.
The abundance of remains in this Canadian formation confirms Gorgosaurus as the best-represented tyrannosaurid in the fossil record. Fossils have also been found further south in the United States, specifically in Montana, coming from geological units like the Judith River Formation and the Two Medicine Formation.
The Laramidian Coastal Plain
During the Campanian, North America was split into two separate landmasses by the Western Interior Seaway, a vast, shallow body of water. Gorgosaurus lived exclusively on the western landmass, known as Laramidia, a narrow strip extending from present-day Alaska to Mexico. Its fossils are found in the coastal plain environment that bordered the western edge of this seaway.
This habitat was lush, humid, and subtropical, more akin to a modern coastal wetland than the dry, cold climate of present-day Alberta and Montana. The mean annual temperature around 75 million years ago is estimated to have been significantly warmer than today, ranging between 16 to 20 degrees Celsius. The landscape consisted of verdant floodplains, river systems, and dense forests.
The ecosystem supported a diverse fauna, including large numbers of hadrosaurs (duck-billed dinosaurs) and ceratopsids (horned dinosaurs). The presence of these large herbivores allowed for the coexistence of other large carnivores, such as the more robust tyrannosaurid Daspletosaurus, suggesting a complex ecological arrangement where predators may have specialized.