Therapsids are a group of synapsid reptiles that lived during the late Paleozoic and throughout the Mesozoic eras. They are often considered ancestors of modern mammals due to their unique features, such as differentiated teeth and a more advanced jaw structure. Therapsids played a crucial role in the evolution of mammals, showcasing adaptations that allowed them to thrive in various environments. These creatures are characterized by their warm-bloodedness and more complex limb structures compared to earlier reptiles. Some well-known therapsids include Dinocephalians and Cynodonts, which exhibited traits that would eventually lead to the emergence of true mammals.