Troodon, a dinosaur recognized for its relatively large brain, roamed the Earth during a specific period of prehistoric time. Understanding its timeline offers insights into its ancient world. This article explores the geological period Troodon existed, the scientific methods used to determine this, and its environment.
Troodon’s Time on Earth: The Late Cretaceous Period
Troodon lived during the Late Cretaceous Period, from approximately 100.5 to 66 million years ago. Specifically, Troodon formosus is known from the Campanian age, about 77 million years ago. Fossil evidence suggests troodontids, including Troodon, persisted until around 70 million years ago, into the early Maastrichtian age. This period is the final chapter of the Mesozoic Era, known as the “Age of Dinosaurs.”
During the Late Cretaceous, Earth’s continents were shifting towards modern configurations. North America, where most Troodon fossils were discovered, was divided by the Western Interior Seaway. This sea split the continent into Laramidia (west) and Appalachia (east). The global climate was warmer than today, a “Greenhouse World” with minimal polar ice caps and no freezing temperatures.
Unearthing the Past: How We Know When Troodon Lived
Paleontologists determine fossil age using relative and absolute dating. Relative dating assesses if a fossil or rock layer is older or younger based on its position in the rock sequence. Lower layers are typically older. This stratigraphic analysis provides chronological order.
For precise age determination, scientists use absolute dating, primarily radiometric dating. This technique measures radioactive isotope decay in igneous rocks (like volcanic ash) found above and below fossil-bearing sedimentary rock. Since fossils are rarely in igneous rock, and carbon-14 dating is unsuitable for millions of years old material, isotopes like uranium and potassium with longer half-lives date these volcanic layers. This provides an age bracket for the fossils.
Troodon fossils have been unearthed from well-dated formations across western North America. The type specimen of Troodon formosus was discovered in Montana’s Judith River Formation (79-75.3 million years ago). Other finds include Alberta’s Horseshoe Canyon Formation (74-67 million years ago) and Wyoming’s Lance Formation (69-66 million years ago). These formations, along with others like Hell Creek (Montana) and Prince Creek (Alaska), provide data points for understanding Troodon’s existence in the Late Cretaceous.
Life in Troodon’s World
During the Late Cretaceous, the North American landscape that Troodon inhabited was diverse and dynamic. Beyond the Western Interior Seaway, coastal plains, estuarine channels, and extensive coal swamps characterized the environment. The climate was warm and humid, supporting lush vegetation. Average annual temperatures reached 16-20 degrees Celsius, fostering a rich, subtropical ecosystem.
The flora consisted of broad-leaved evergreen woodlands and conifers, though flowering plants were also present. Troodon shared this world with a wide array of other dinosaurs, including large plant-eaters like hadrosaurs and ceratopsians, armored ankylosaurs, and predators such as tyrannosaurs and other dromaeosaurs. Smaller animals, including early mammals, turtles, and crocodilians, also thrived alongside Troodon.
Troodon, a bipedal dinosaur around 6.5 to 11.5 feet long and 2.5 to 3 feet tall, occupied a distinct niche within this ecosystem. Its forward-facing eyes suggested keen vision, possibly indicating a nocturnal hunting strategy. While initially classified as a carnivore, the unique serrations on its teeth, resembling those of some herbivorous reptiles, suggest it may have had an omnivorous diet, consuming both small prey and plant matter. Its relatively large brain for a dinosaur also points to an active and adaptable lifestyle within its Late Cretaceous environment.