The “Triassic Park” concept often conjures images of towering dinosaurs from popular culture. However, the true Triassic Period, spanning approximately 252 to 201 million years ago, represents a distinct chapter in Earth’s deep history. This era marked a time of significant beginnings, as life on Earth embarked on a remarkable recovery and diversification following an immense global catastrophe. It set the stage for the emergence of many animal groups that would later define the Mesozoic Era.
Unpacking the Triassic Period
The Triassic Period was the initial period of the Mesozoic Era, lasting about 50.5 million years, from 251.9 to 201.4 million years ago. At its start, all major landmasses were fused into a single supercontinent, Pangea, which stretched across the globe from pole to pole. This vast landmass was surrounded by the immense Panthalassa Ocean, with the Tethys Ocean nestled within the supercontinent’s arc.
The global climate during the Triassic was predominantly hot and dry, characterized by widespread deserts across much of Pangea’s interior. Coastal regions often experienced highly seasonal monsoon climates. This period followed the Permian-Triassic extinction event, the most severe known mass extinction in Earth’s history, which wiped out an estimated 85% to 95% of marine invertebrate species and 70% of terrestrial vertebrate genera.
Inhabitants of the Triassic World
Reptiles, particularly archosaurs, became the dominant terrestrial vertebrates. Archosaurs, a group that includes the ancestors of modern crocodiles and birds, diversified into various forms.
The earliest dinosaurs, such as Eoraptor and Herrerasaurus, first appeared in the Late Triassic, around 233 million years ago, primarily in regions that are now Argentina and Brazil. These early dinosaurs were often small, agile, bipedal predators, and were not yet the dominant land animals. Pseudosuchians, which were crocodile-like archosaurs, were the primary predators during much of the Triassic, including large carnivorous “rauisuchians” and heavily armored, herbivorous aetosaurs.
Beyond the land, pterosaurs, the first flying vertebrates, emerged in the Norian stage of the Late Triassic, quickly spreading across the globe. Oceans saw the return and diversification of marine reptiles like ichthyosaurs, often referred to as “fish lizards,” and the appearance of early plesiosaurs. The Triassic also saw the initial appearance of early mammals, which were generally small, mouse-sized creatures, and the diversification of amphibians, including large aquatic temnospondyls.
The End of the Triassic Era
The Triassic Period concluded with another significant global catastrophe, the Triassic-Jurassic Extinction Event, approximately 201 million years ago. This event is considered one of the five major mass extinctions in Earth’s history. The leading hypothesis for its cause points to massive volcanic activity within the Central Atlantic Magmatic Province (CAMP).
These extensive eruptions released large amounts of carbon dioxide and sulfur dioxide into the atmosphere, leading to global warming and ocean acidification. In the oceans, about 23% to 34% of marine genera disappeared, with corals and conodonts suffering severe losses. On land, nearly all archosauromorph reptiles, except for crocodylomorphs, dinosaurs, and pterosaurs, went extinct. This extinction cleared numerous ecological niches, allowing the surviving dinosaurs to diversify and become the dominant terrestrial vertebrates in the subsequent Jurassic Period.