Dimetrodon was a prehistoric synapsid that lived during the Early Permian period, around 295 to 272 million years ago. Measuring up to 4.6 meters (15 feet) in length, it was characterized by a large, sail-like structure on its back, formed by elongated neural spines, which was likely used for thermoregulation or display. Dimetrodon had a robust skull with sharp, serrated teeth, indicating it was a carnivorous predator. Its fossils have been found primarily in North America, providing important insights into the evolution of early terrestrial vertebrates before the age of dinosaurs.