During the time dinosaurs roamed Earth, the planet’s geography differed profoundly from today. Continents were not fixed, but part of a dynamic system that continuously reshaped the surface. This movement led to dramatic changes in coastlines, climates, and the distribution of life. Understanding this ancient geography illustrates the environments in which dinosaurs lived and evolved.
When All Lands Were One
Approximately 250 million years ago, at the dawn of the Mesozoic Era, all of Earth’s major landmasses merged into a single supercontinent named Pangea. This C-shaped landform stretched from near the northern to the southern polar regions. A vast global ocean, Panthalassa, surrounded Pangea. This allowed terrestrial animals, including early dinosaur ancestors, to freely migrate across much of the planet. Pangea began breaking apart around 200 million years ago, marking the beginning of the Jurassic period.
The Early Dinosaur World
During the Triassic Period, Pangea began to rift and fragment. This led to its separation into two main landmasses: Laurasia in the north and Gondwana in the south. Laurasia encompassed what would become North America, Europe, and Asia, while Gondwana included future South America, Africa, Antarctica, Australia, and India. Between them, the Tethys Ocean began to form. Its interior generally experienced arid conditions due to distance from oceanic moisture.
A Shifting Landscape
The Jurassic Period saw further fragmentation of Earth’s landmasses. Rifting between North America and Africa marked the initial opening of the Central Atlantic Ocean. This ocean remained relatively narrow during the Jurassic, but steadily widened as the continents pulled further apart. In the Southern Hemisphere, Gondwana also began to break apart. Madagascar and Antarctica started to rift away from Africa, leading to the formation of the western Indian Ocean.
South America began to separate from Africa, though the full opening of the South Atlantic Ocean would occur later. India, which was still connected to Australia and Antarctica as part of East Gondwana, also started its northward journey. These movements created new coastlines and inland seas, such as the Turgai Epicontinental Sea, which formed a marine barrier between Europe and Asia. This reshaping influenced global climates and fostered the diversification of life.
The Continents at Dinosaur’s End
By the Cretaceous Period, continents were significantly closer to their modern positions, though still distinct. The Atlantic Ocean continued to widen, with the South Atlantic fully opening as South America separated from Africa. India continued its rapid northward drift, separating from Madagascar around 88 million years ago and becoming an isolated island continent. Australia remained connected to Antarctica for much of this period, both situated closer to the South Pole.
Cretaceous fragmentation led to greater geographical isolation of dinosaur populations, contributing to the evolution of diverse, unique species. New mountain ranges also formed as plates collided, altering the global landscape. By the end of the Cretaceous, most modern continents were separated by expanding oceans.
How We Know Continents Move
Scientists reconstruct ancient continental configurations using plate tectonics, which describes Earth’s outer shell as large, moving plates. Evidence includes the fit of continental coastlines, like South America’s eastern coast and Africa’s western coast. Similar rock formations and geological structures on now-separated continents also indicate past connections; for instance, ancient rock belts along the Brazilian coast align with those in West Africa.
The distribution of identical fossils across different continents further supports this. Fossils of the freshwater reptile Mesosaurus have been found in Brazil and South Africa, suggesting these landmasses were once joined. Similarly, Glossopteris plant fossils have been discovered in Africa, South America, India, and Antarctica, indicating a shared landmass. These combined lines of evidence allow researchers to piece together Earth’s continental history.