Allosaurus

# Evolutionary Timeline of Allosaurus Allosaurus, a large theropod dinosaur, evolved during the Mesozoic Era, specifically thriving in the Late Jurassic period around 155–145 million years ago. Its evolutionary history traces back to early theropods, with key adaptations for predation shaped by environmental pressures like climate changes, prey abundance, and competition. ### Key Milestones - **Triassic Origins ( ~230–200 Ma)**: Ancestral theropods like *Coelophysis* emerge, small and agile, adapting to arid environments post-Permian extinction. - **Early Jurassic Diversification ( ~200–174 Ma)**: Theropods evolve larger sizes and bipedalism; groups like Dilophosauridae branch off, facing pressures from expanding forests and diverse prey. - **Middle Jurassic Transition ( ~174–163 Ma)**: Carnosauria clade develops, with ancestors like *Megalosaurus* showing enhanced jaw strength amid volcanic activity and sea level changes. - **Late Jurassic Dominance ( ~163–145 Ma)**: *Allosaurus* appears as an apex predator in North America and Europe, evolving serrated teeth and strong limbs to hunt large sauropods, influenced by seasonal floods and megaherbivore herds. - **Extinction and Legacy ( ~145 Ma)**: End-Jurassic events lead to decline; influences later theropods like tyrannosaurids through shared traits.