Dimetrodon - Lord of Euramerica

On most pictures, he looks slow and sluggish - and he surely wasn't anything sylphlike - but I like this old dead fellow! Of course, he was no dinosaur, but a quadrupedal, sail-backed synapsid that lived during the Early Permian, around 299–270 million years ago and is famous for the large sail on its back formed by elongated spines extending from the vertebrae.
Fossils of Dimetrodon are known from the US and Germany, areas that were part of the supercontinent Euramerica (or the "Old Red Sandstone" Continent) during the Early Permian.
Dimetrodon was part of the "Permo-Carboniferous chronofauna," that dominated the continental Euramerican ecosystem for several million years. Based on the geology of deposits like the Red Beds, Dimetrodon is thought to have inhabited a well-vegetated lowland deltaic ecosystem.