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pelycosaur
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Illustration of a Dimetrodon, an extinct pelycosaur, showing a reptile-like animal with a large, sail-like fin on its back, squat legs, and a long tail. A scale bar in the corner indicates size. Illustration of the extinct Edaphosaurus, a pelycosaur, showing a reptile-like animal with a large, sail-like fin on its back, squat limbs, and a long tail. A scale bar indicates size.
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pelycosaur

fossil tetrapod order
Also known as: Pelycosauria
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Illustration of a Dimetrodon, an extinct pelycosaur, showing a reptile-like animal with a large, sail-like fin on its back, squat legs, and a long tail. A scale bar in the corner indicates size.
Dimetrodon Dimetrodon, an extinct relative of primitive mammals, lived from about 286 million to 270 million years ago, during the Permian Period, in the section of Pangea that would eventually split off to become North America. Dimetrodon was more than 3.5 metres (11.5 feet) long, and its large “sail” was likely used for thermoregulation.

Pelycosauria was an order of extinct, primitive, synapsid vertebrates that lived primarily during the Permian Period. These animals, which are not reptiles or dinosaurs, are considered early relatives of mammals.1234

Key characteristics of pelycosaurs include:
* Appearance: Many pelycosaurs, such as Dimetrodon and Edaphosaurus, developed a distinctive large, sail-like structure on their backs, formed by elongated vertebral spines connected by a membrane.24
* Diet: This group included both carnivores like Dimetrodon and herbivores like Edaphosaurus.24
* Evolutionary Significance: Pelycosaurs are significant because they likely gave rise to the therapsids, a group that eventually led to mammals.234

Fossils of pelycosaurs are commonly found in North America, particularly in Texas.23

Summary created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
7 Britannica Sources
  1. Dimetrodon
  2. pelycosaur
  3. Permian Period - Emergence of important reptiles
  4. reptile - Fossil distribution
  5. Pelycosauria
  6. sauropterygian
  7. Edaphosaurus

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