Dimetrodon is a genus of extinct synapsid that lived around 295–272 million years ago. It belongs to the family Sphenacodontidae. The genus was first described in 1878, and since then, more than a dozen species have been assigned to this genus. Dimetrodon is commonly mistaken as contemporary of dinosaurs or belonging to the clade Dinosauria, but the real fact is that they went extinct around 40 million years before even Dinosaurs evolved. Dimetrodon is more closely related to mammals rather than reptiles. However, it is not a direct descendant of mammals.

Physical Characteristics

They had a tall, curved and laterally compressed skull. The eye sockets were placed far back in the skull. Behind every eye socket, there was single hole named infratemporal fenestra. It had large, powerful jaws with two types of teeth – sharp canines and shearing teeth. Remains suggested that sexual dimorphism was present in the genus. Males were slightly larger than the females. They possessed a long tail consisting around fifty caudal vertebrae. One of its distinctive features was its large sail made of elongated neural spines broadening from the vertebrae. There are several hypotheses offered by the paleontologists regarding the use of the sail, such as thermoregulatory function, sexual display or dominance rituals.

Species

Dimetrodon angelensis	Valid
Dimetrodon booneorum	Valid
Dimetrodon cruciger	Synonym of Edaphosaurus cruciger
Dimetrodon dollovianus	Valid
Dimetrodon giganhomogenes	Valid
Dimetrodon gigas	Synonym of Dimetrodon grandis
Dimetrodon grandis	Valid
Dimetrodon incisivus	Synonym of Dimetrodon limbatus
Dimetrodon kempae	Possible nomen dubium
Dimetrodon limbatus	Valid
Dimetrodon longiramus	Synonym of Secodontosaurus obtusidens
Dimetrodon loomisi	Valid
Dimetrodon macrospondylus	Valid
Dimetrodon milleri	Valid
Dimetrodon natalis	Valid
Dimetrodon occidentalis	Valid
Dimetrodon platycentrus	Synonym of Dimetrodon macrospondylus
Dimetrodon rectiformis	Synonym of Dimetrodon limbatus
Dimetrodon semiradicatus	Synonym of Dimetrodon limbatus
Dimetrodon teutonis	Valid

Discovery

This genus has been described from several fossil and some footprint samples by American paleontologist and comparative anatomist Edward Drinker Cope. Its skeleton remains have been found in the southwestern United States, mostly in a geological deposit called the Red Beds in Texas and Oklahoma. Recently, fossil samples have been found in Germany. Trackways have been found in Nova Scotia, Canada.

American paleontologist EC Case studied this genus in the first few decades of the 20th century and named few more species. In the late 1920s, American paleontologist and biologist Alfred Romer, who was a specialist in vertebrate evolution, reanalyzed many Dimetrodon specimens and named a few new species. Dimetrodon specimens were found and described from places outside Texas and Oklahoma, such as Utah and Arizona. Remains have also been found from Ohio and New Mexico.

In the year 2001, a new species Dimetrodon teutonis was named. The remains of it were unearthed from Lower Permian Bromacker at Thuringian Forest in Germany, proving that the species of this genus also existed outside North America.

Behavior and Adaptation

They shared their habitat with Eryops and Diplocaulus. It is believed that they were fast runners. They were one of the top predators in its ecosystem, probably feeding on fish, reptiles, amphibians, insects, tetrapods and pelycosaurs. Smaller species of this genus might have different ecological roles. They were cold-blooded creatures. They were mostly active during the day.

Etymology

The name Dimetrodon has come from words “Di” meaning “twice” in modern Latin, “Metron” meaning “measure” in Greek, and “Odous” meaning “tooth.”

Interesting Facts

• An adult Dimetrodon could take around 60 – 90 minutes raise its temperature from 79°F to 90°F.
• Dimetrodon has appeared in several documentary films (BBC’s walking with monsters), toy-lines (bullyland) and games (Jurassic World: The Game).