Quck answer
Dimetrodon was not a dinosaur. Despite its reptilian appearance, it actually belonged to a different group of animals called synapsids. Synapsids are characterized by their skull structure, which includes a single temporal opening on each side of the skull. Dinosaurs, on the other hand, belong to a group called archosaurs, which have two temporal openings on each side of the skull. Dimetrodon lived during the Permian period, about 295 to 272 million years ago, predating the first dinosaurs by about 40 million years. Dimetrodon was a dominant predator of its time, with its sail-like structure likely used for thermoregulation or display.
Extinct Animals
The sail on the back of Dimetrodon, a prehistoric predator that roamed North America and Europe about 295 to 275 million years ago, is a distinctive feature of its skeleton. Wolfgang Kaehler/LightRocket/Getty Images
Dimetrodon, a prehistoric predator that lived between 295 and 275 million years ago in North America and Europe, is not a dinosaur but a synapsid, according to University of Chicago paleontologist Caroline Abbott. Abbott explains that synapsids are one of the two separate lineages that emerged around 310 million years ago from the first amniotes, which are vertebrates capable of laying eggs on dry land. The other lineage is the reptiles. Synapsids are the animal clade that gave rise to mammals like humans. The Dimetrodon is one of the earlier synapsids, meaning it had closer evolutionary ties with humans than any modern reptiles or dinosaurs.
Part of the Synapsid Family
Hans Sues, curator of vertebrate paleontology at the Smithsonian National Museum of Natural History, explains that the presence of a large opening behind the eye socket on the skull is the key feature of all animals in the evolutionary lineage leading to mammals. This feature becomes much larger in more advanced species and houses the jaw-closing muscles. Synapsids have this feature, including the Dimetrodon. Another clue that tipped off fossil hunters was that the Dimetrodon was a heterodont, meaning its teeth did not all look the same. Its teeth had different shapes and functions, with incisor-like front teeth, a large canine, and smaller teeth behind the canine.
Neural Spines
The sail on the back of the Dimetrodon was made up of long, rod-like neural spines. These spines are the knobby columns of bone that sit on top of the vertebrae. In animals that walk on all fours, the neural spines point vertically. In humans, they point backward. The tallest neural spines on the Dimetrodon were in the middle of its back, giving the sail a “dumbbell” shape. The sail in the largest Dimetrodon, which could grow up to 15 feet long and weigh 550 pounds, would have stood at least 5 feet off the ground, slightly taller than a typical sedan car.
The Sail of Dimetrodon
The purpose of the sail on Dimetrodon’s back remains a mystery as there are no living animals with such sails that can be used for comparison. According to Sues, researchers do not know the reason behind the sail on Dimetrodon’s back. The tall neural spines with tissue and blood vessels in between may have provided a lot of surface area to help with thermoregulation, or how an animal maintains ideal body temperatures. Abbott suggests that the sail may have acted as a giant solar panel, providing energy for Dimetrodon to move and hunt. However, researchers have doubts about these theories.
Another possibility is that the sail was used for sexual selection. Abbott notes that, sometimes, ornamental structures evolve due to mate preferences, and a sail for sexual display would have come about because other Dimetrodon found it appealing for mate choice. However, the real purpose of the structure remains unknown.
Despite its unknown purpose, the sail was not unique to Dimetrodon. Other prehistoric creatures, such as Edaphosaurus and Platyhystrix, also had prominent back sails, and some dinosaurs independently evolved the same feature.
Dimetrodon is not a Dinosaur
Dimetrodon was not a dinosaur, but a forerunner of mammals that lived during the early part of Earth’s Permian Period. The creature had nothing to do with T. rex, Triceratops, or Spinosaurus. However, it is often mistakenly labeled as a “dinosaur” in toy sets and plastic figurines. The sail-backed dinosaur Spinosaurus, which lived during the Cretaceous Period, is commonly mistaken for Dimetrodon’s ancestor. The Permian synapsid died out tens of millions of years before the first dinosaurs even showed up.
Skin Impressions Are Missing from Dimetrodon Fossil Evidence
Dimetrodon walked on four legs, unlike Spinosaurus, which was bipedal. The fossil evidence indicates this. However, other aspects of Dimetrodon’s appearance and behavior remain unclear.
Although scientists have not found skin impressions associated with Dimetrodon bones, they believe the animal had scales and no hair. This is due to the limited information available on when hair evolved in synapsids and indirect evidence from trackways, as explained by Abbot.
Recently, scientists discovered traces of prominent stomach scales left behind by an early Permian synapsid. It’s believed that the animal who made them was similar to Dimetrodon.
Hair-like structures have been found in coprolites from the Late Permian, but these are from 10 to 20 million years after the last Dimetrodon. It’s known that synapsid hair must have evolved by 164 million years ago.
Dimetrodon came in different sizes, with 14 named species, one of which was initially placed in the genus Barygnathus. The animals ranged from about 5 feet to roughly three times longer.
This information is useful for aspiring paleoartists.
FAQ
1. What is Dimetrodon?
Dimetrodon is an extinct genus of synapsids, often mistaken for dinosaurs. They lived during the Permian period, before the dinosaurs appeared.
2. How big was Dimetrodon?
Dimetrodon was a large animal, with some species growing up to 4.5 meters (15 feet) in length and weighing around 250 kg (550 lbs).
3. Why is Dimetrodon not a dinosaur?
Dimetrodon is not a dinosaur because it belongs to a different group of reptiles called synapsids, which are characterized by having a single hole in the skull behind each eye. Dinosaurs belong to a different group called archosaurs, which have two holes in the skull behind each eye.
4. What did Dimetrodon eat?
Dimetrodon was a carnivore and probably preyed on small animals such as insects, amphibians, and reptiles.
5. What was the role of Dimetrodon in the ecosystem?
Dimetrodon was an important predator in the Permian ecosystem, controlling the populations of smaller animals and keeping the food chain in balance.
6. How long did Dimetrodon live?
Dimetrodon lived during the Permian period, which lasted from about 299 million to 251 million years ago. The genus itself existed for around 25 million years.
7. What is the closest living relative to Dimetrodon?
The closest living relative to Dimetrodon is the mammals, which also belong to the synapsid group. Humans, dogs, cats, and whales are all examples of mammals.
8. How do we know what Dimetrodon looked like?
We know what Dimetrodon looked like from fossils that have been found and studied by paleontologists. These fossils include bones, teeth, and even some well-preserved skin impressions.
9. How did Dimetrodon reproduce?
Very little is known about the reproductive behavior of Dimetrodon. However, it is believed that they laid eggs like most reptiles.
10. What caused the extinction of Dimetrodon?
The exact cause of the extinction of Dimetrodon is not known, but it is believed to have been a combination of factors including climate change, competition for resources, and possibly disease.
11. Why is it important to know the difference between Dimetrodon and dinosaurs?
It is important to know the difference between Dimetrodon and dinosaurs because they belonged to different groups of reptiles and had different roles in the ecosystem. Misconceptions about Dimetrodon being a dinosaur can lead to confusion and errors in scientific research and education.
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