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Description
Reconstruction of the sphenacodontid pelycosaur Dimetrodon grandis from the Early Permian of Oklahoma and Texas (USA). I started this work back in 2018 and even drew a head and torso without a sail, but soon abandoned it. Later, I tried to revive it by changing the position of the tail (initially it was more undularly curved), but I did not go beyond a pencil sketch of the parts untouched by the pen. In January of this year, I finally took up Dimetrodon seriously. In the process, soft tissues were added to the jaws, teeth were corrected, tail, legs and sail were drawn, and wrinkles were added to the skin of the neck and trunk. I'm glad I finally drew this species.

Dimetrodon is one of the most famous animals of the Paleozoic era. Its numerous remains were collected in the Red Beds of Texas along with the bones of other Early Permian vertebrates. They were studied by paleontologist E.D. Cope in the 1870s. He described several species of this genus, the first of which, D. limbatus, was originally named Clepsydrops limbatus. Later, dimetrodon was studied by paleontologists such as E.C. Case and A.S. Romer. Over time, the number of species grew to 20, but many of them were later synonymized with other animals or with each other. Most Dimetrodon are found in several US states, one species from Prince Edward Island (Canada) was long known as Bathygnathus and assigned to the genus Dimetrodon in 2015, and the smallest species, D. teutonis, comes from the Bromacker location in Germany.

Dimetrodons varied in size and sail shape, but they all had proportionally large, tall, and laterally compressed skulls. Large "fangs" stand out among the teeth (hence the name, meaning "teeth of two sizes"). The teeth have a cutting edge, and in large species it is equipped with denticles. There is a notch in the upper jaw for capturing prey. The high preorbital area accommodates long tooth roots and a large nasal cavity. The tip of the lower jaw is massive. There is a special ridge in the back of the lower jaw, a reflective plate that could be connected to the auditory mechanism. The neck of the Dimetrodon is short, the body is long and compressed from the sides. The tail was originally described as very short because only the first 11 vertebrae were known to taper rapidly towards the tip. In 1927, it became clear that the tail was longer. The sail consists of very long spinous processes, the bases of which were surrounded by dorsal muscles during life. A skin membrane was stretched over these spikes. Initially, it was believed that the membrane reached all the way to the tips of the spines, but the curvature of the processes in some samples may indicate the edge of the sail free from the membrane. It was generally believed that the sail served to quickly heat up and dissipate excess heat, but the presence of it in small species, the existence of sphenacodontids with smaller dorsal ridges and the relatively rapid growth of the sail may speak in favor of a rather display function. Dimetrodon inhabited mainly swampy lowlands, although some species (for example, D. teutonis) lived in mountainous areas. There is evidence that it was an opportunistic predator: its teeth were found among the large cartilaginous elements of xenacanthid sharks, and bite marks are found on the bones of amphibians and even other Dimetrodon.

This Dimetrodon is depicted in the "high walk" pose, which is now adopted by monitor lizards and crocodiles. The skin is mostly naked, but the belly and underside of the tail are covered with shields based on a possible skin impressions from the underside of a pelicosaur from Poland (www.tandfonline.com/doi/abs/10… ). The presence of scales would be strange against the background of the connection of sphenacodonts with therapsids that had scaleless skin. However, the true identity of the skin impressions is unknown (they could have been left by a form more distantly related to therapsids) and therefore my reconstruction of the skin is speculative.

Black gel ink pen, 2024.

Description
Reconstruction of the sphenacodontid pelycosaur Dimetrodon grandis from the Early Permian of Oklahoma and Texas (USA). I started this work back in 2018 and even drew a head and torso without a sail, but soon abandoned it. Later, I tried to revive it by changing the position of the tail (initially it was more undularly curved), but I did not go beyond a pencil sketch of the parts untouched by the pen. In January of this year, I finally took up Dimetrodon seriously. In the process, soft tissues were added to the jaws, teeth were corrected, tail, legs and sail were drawn, and wrinkles were added to the skin of the neck and trunk. I'm glad I finally drew this species.

Dimetrodon is one of the most famous animals of the Paleozoic era. Its numerous remains were collected in the Red Beds of Texas along with the bones of other Early Permian vertebrates. They were studied by paleontologist E.D. Cope in the 1870s. He described several species of this genus, the first of which, D. limbatus, was originally named Clepsydrops limbatus. Later, dimetrodon was studied by paleontologists such as E.C. Case and A.S. Romer. Over time, the number of species grew to 20, but many of them were later synonymized with other animals or with each other. Most Dimetrodon are found in several US states, one species from Prince Edward Island (Canada) was long known as Bathygnathus and assigned to the genus Dimetrodon in 2015, and the smallest species, D. teutonis, comes from the Bromacker location in Germany.

Dimetrodons varied in size and sail shape, but they all had proportionally large, tall, and laterally compressed skulls. Large "fangs" stand out among the teeth (hence the name, meaning "teeth of two sizes"). The teeth have a cutting edge, and in large species it is equipped with denticles. There is a notch in the upper jaw for capturing prey. The high preorbital area accommodates long tooth roots and a large nasal cavity. The tip of the lower jaw is massive. There is a special ridge in the back of the lower jaw, a reflective plate that could be connected to the auditory mechanism. The neck of the Dimetrodon is short, the body is long and compressed from the sides. The tail was originally described as very short because only the first 11 vertebrae were known to taper rapidly towards the tip. In 1927, it became clear that the tail was longer. The sail consists of very long spinous processes, the bases of which were surrounded by dorsal muscles during life. A skin membrane was stretched over these spikes. Initially, it was believed that the membrane reached all the way to the tips of the spines, but the curvature of the processes in some samples may indicate the edge of the sail free from the membrane. It was generally believed that the sail served to quickly heat up and dissipate excess heat, but the presence of it in small species, the existence of sphenacodontids with smaller dorsal ridges and the relatively rapid growth of the sail may speak in favor of a rather display function. Dimetrodon inhabited mainly swampy lowlands, although some species (for example, D. teutonis) lived in mountainous areas. There is evidence that it was an opportunistic predator: its teeth were found among the large cartilaginous elements of xenacanthid sharks, and bite marks are found on the bones of amphibians and even other Dimetrodon.

This Dimetrodon is depicted in the "high walk" pose, which is now adopted by monitor lizards and crocodiles. The skin is mostly naked, but the belly and underside of the tail are covered with shields based on a possible skin impressions from the underside of a pelicosaur from Poland (www.tandfonline.com/doi/abs/10… ). The presence of scales would be strange against the background of the connection of sphenacodonts with therapsids that had scaleless skin. However, the true identity of the skin impressions is unknown (they could have been left by a form more distantly related to therapsids) and therefore my reconstruction of the skin is speculative.

Black gel ink pen, 2024.