Mammal Dinosaur

On first instinct you might think that this is another type of dinosaur, but actually it is more closely related to mammals then dinosaurs or lizards. Dimetrodon is really a non-mammal synapsid that went extinct during the Permian extinction. Its "sail" is elongated vertebra that was filled with blood vessels. Dimetrodon could use the sail to change is body temperature by either facing into the sun to heat up or face away from the sun to cool down. Dimetrodon was not the only non-mammal synapsid; there were multiple different branches of non-mammal synapsids which are now extinct. Non-mammal synapsids were a dominating group before the Permian extinction.

Dimetrodon