Dimetrodon

The first reptilian apex predator

Dimetrodon possessed a significant evolutionary advantage over other animals of its time: a dorsal sail.

The large sail did not simply serve representational purposes. Above all, it helped the reptile Dimetrodon to regulate its body temperature. Because Dimetrodon was cold-blooded, its body could only reach operating temperature with the help of the sun. Since the dorsal sail enlarged the body surface by almost 50 per cent, the sun had much more surface area to warm it.

Before daybreak, the carnivore Dimetrodon waited listlessly. But as soon as the first rays of sunlight hit the large dorsal sail, the rapid warming accelerated its metabolism, and it was able to go hunting an hour before all the other animals.

In the hot midday hours, Dimetrodon turned its sail away from the sun to avoid overheating, releasing heat again. This evolutionary system for regulating body heat was to be used by mammals millions of years later, albeit in a different form. And we humans, too: For our ability to sweat is nothing other than the further development of the sail on the back of a 300-million-year-old reptile. 

And there were even more parallels between Dimetrodon and mammals: Although Dimetrodon was a reptile, its body already had mammal-like features. Jaws, teeth, dorsal sail, and sensory organs markedly distinguished it from most reptiles of its time. Dimetrodon was a precursor of the therapsids, the so-called mammal-like reptiles, such as Gorgonops, from which mammals were to evolve over hundreds of millions of years in the shadow of the dinosaurs.

Dimetrodon thus sits in more ways than one at the beginning of a long branch on the family tree of life.