Spinosaurus

# Evolutionary Timeline of Spinosaurus Spinosaurus, a genus of theropod dinosaurs, evolved during the Mesozoic Era, showcasing remarkable adaptations from terrestrial ancestors to semi-aquatic predators. Its evolutionary history is marked by transitions driven by environmental pressures such as changing climates, rising sea levels, and abundant aquatic prey in North African river systems. Key ancestors include basal tetanurans and early spinosaurids, leading to specialized features like elongated spines for sails and aquatic locomotion. ### Key Milestones: - **Late Jurassic (160-150 million years ago):** Emergence of early spinosaurids from tetanuran theropods, adapting to diverse environments with initial carnivorous traits. - **Early Cretaceous (130-110 million years ago):** Diversification of Spinosauridae, with ancestors like Baryonyx developing fish-eating habits amid humid, riverine habitats. - **Mid-Cretaceous (112-99 million years ago):** Evolution of Spinosaurus aegyptiacus, featuring sail-backed morphology for thermoregulation or display, and aquatic adaptations like dense bones for buoyancy control, influenced by coastal flooding and fish-rich ecosystems. - **Late Cretaceous (99-93 million years ago):** Peak of Spinosaurus diversity, with species like S. maroccanus facing extinction pressures from climate shifts and asteroid impact, leading to the end of non-avian dinosaurs.