Final answer:
The Dimetrodon is an ancient cold-blooded creature with scaly skin that came before the dinosaurs. It was a type of pelycosaur and is part of the synapsid group, which became the most common land vertebrates during the Permian Period.
Step-by-step explanation:
The ancient cold-blooded creature that has scaly skin and came before the dinosaurs is the Dimetrodon. Dimetrodon is a type of pelycosaur, which were synapsids. Synapsids became the most common land vertebrates during the Permian Period, evolving some traits of mammals. The earliest therapsids, a group of animals descended from pelycosaurs, lived about 260 million years ago.