The Dimetrodon genus can immediately be identified by its iconic spine, a huge extension of its vertebrae that could grow over 5 feet tall. The purpose of the spine sail is unknown, though speculation ranges from courtship displays to temperature regulation. More recent studies have shown that the spines lacked the necessary channels for carrying blood vessels. A study in 2012 in conjunction with NASA's Jet Propulsion Laboratory suggests the sail may have served as a spring-like energy storage device for fast locomotion, allowing for the Dimetrodon to quickly close in on prey.

Dimetrodon was certainly not the only creature with such a spine sail. Take Spinosaurus, a dinosaur that emerged much later in the fossil record with little relation to Dimetrodon. Both animals sported the fashionable back sail due to convergent evolution, a process where two unrelated animals develop similar features and lifestyles. As with Dimetrodon, debate continues around what purpose the Spinosaurus’ eponymous spine served, though it is clear there is still much to learn about these striking anatomical features.

The Permian Period that the Dimetrodon thrived in represents a radical change to life in response to a more varied climate across the planet. It was a transition from the warm, swampy jungles of the Carboniferous Period towards a more arid climate. The supercontinent Pangea had formed into the single landmass on the planet, with an interior that held stretches of dry deserts within. In the oceans, we see the first true bony fish. On land, the evolution of amphibian life gives way to pure terrestrial animals, including Dimetrodon and the other synapsids.

During the Permian Period, terrestrial life was defined by the amniotes, who had evolved during the Carboniferous. Amniotes were the first animals to evolve an external eggshell, diverging from the amphibians by being able to reproduce without a water source. With this evolutionary feature, amniotes were able to dominate life on land and diversify, dividing into two clades, synapsids and sauropsids. The main difference between the two was in their skulls, synapsids having one temporal fenestra (an opening in the skull behind the eye) and sauropsids having two, or none at all.

Superficially, synapsids and sauropsids appeared similar, but the divergence between the two would lead in very different directions, with sauropsids evolving into dinosaurs and synapsids becoming mammals. The Dimetrodon is a good example of this, the animal refining a number of traits that we humans use today, although Dimetrodon is not a direct ancestor of mammals. The genus’ teeth are similar to our own in that we also have varied shapes to our teeth that allow us to break down food effectively. Dimetrodon also had a somewhat upright posture which is also in line with mammals.

The evolutionary branches between today’s mammals and the Permian’s Dimetrodon are far apart, but the connection can be found in subtle anatomical features that appeared around 280 million years ago. The Dimetrodon is a testament to just how long evolution’s story is, that our own species is distantly related to a reptilian-like predator that crushed its prey with serrated teeth and sported massive neural spines. With these attributes, the Dimetrodon dominated the world’s food chains of the Permian Period for millions of years.

This specimen is a fossil fragment of a Dimetrodon neural spine sail, originally featured in the Second Edition of the Mini Museum. The material was recovered from private land in West Texas, USA. This region, known as the Texas Red Beds, contains one of the most complete fossil records of the Early Permian and dates to roughly, 280,000,000 years old.

These fragments of Dimetrodon neural spine sail material vary by size, color and shape. The ancient Permian Period material is quite precious and it is rare to see in public hands.

Check out our full Dimetrodon fossil collection, with riker box specimens, several larger segments of neural spine fossils and even a complete showcase dorsal vertebra! Explore the Dimetrodon collection here!