Relationship with mammals
Dimetrodon grandis, along with other Dimetrodon species, is often mistakenly lumped together with Dinosauria in nonscientific settings. More than simply being inaccurate, this discounts the unique and interesting evolutionary position of Dimetrodon. Dimetrodon is actually a synapsid, and more closely related to mammals than dinosaurs or other reptile species. As such, there are many early mammalian traits that can be seen in their morphology. One of these traits is the temporal opening in the skull of Dimetrodon. This is an opening in the side of the skull that is used in jaw muscle attachment and one that is seen in mammals today (1).
The nasal cavity of Dimetrodon also identifies it as a relative to mammals. The inner surface of the skull shows evidence of nasoturbinal ridges, though not so large as later synapsids. Nasoturbinals are structures that increase surface area inside the nasal cavity. Large nasoturbinals are considered to be a sign of endothermy, due to their ability to dissipate heat. Dimetrodon appears to show a transitional form of this feature (2).
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