Spinosaurus, meaning "spine lizard," was a massive predatory dinosaur that roamed the Earth during the Cretaceous period. It is characterized by its distinctive sail-like structure on its back, formed by elongated neural spines, which could have served various purposes including thermoregulation and display. With a length exceeding 50 feet and weighing up to 20 tons, Spinosaurus is one of the largest known carnivorous dinosaurs, possessing a crocodile-like snout with dangerously sharp teeth.