In the Middle Triassic, the first primitive dinosaurs appear, small and swift bipedal reptiles.
A large-scale extinction wave removes many competing reptile species, allowing dinosaurs to become the dominant land animals.
Enormous herbivorous sauropods such as Diplodocus and Brachiosaurus dominate the landscapes of the Jurassic.
Archaeopteryx, a transitional form between dinosaurs and birds, develops in the Late Jurassic.
In the early Cretaceous, the first angiosperms appear, drastically changing vegetation and ecosystems.
Species such as Tyrannosaurus rex, Triceratops and Ankylosaurus dominate a rich and diverse ecosystem.
A massive asteroid strikes near what is now the Yucatán Peninsula, causing worldwide devastation.
Most dinosaur species become extinct as a result of the climatic effects of the asteroid impact.
A small group of feathered dinosaurs survives the mass extinction and evolves further into modern birds.
Fossils such as Eoraptor and Herrerasaurus, found in present-day Argentina, are among the earliest known dinosaurs. These animals were small, lightly built, and lived alongside other reptiles such as the dominant crurotarsans. Their emergence marks the beginning of a dynasty that would last more than 165 million years. The environment consisted of dry plains and mixed woodland areas under a warm and variable Triassic climate.