New ecosystems with lots of plants allowed large, plant-eating animals to evolve—but only a few kinds at first. Sail-backed Dimetrodon and other meat eaters mostly ate other carnivores.

Like many meat eaters, Dimetrodon had curved, knifelike teeth with serrated edges for cutting through flesh. It was the top predator of its time.
This sail-backed animal is not a dinosaur. It lived millions of years earlier and belongs to the synapsids, a group that also includes mammals.

The bony rods along its backbone probably supported a thin, fleshy sail. The sail’s function is still a mystery—perhaps it helped the animal control body temperature, attract mates, or recognize others of its own kind.


With so few big plant eaters on land at the beginning of the Permian, how did a large carnivore like Dimetrodon find enough to eat?"

It hunted other carnivores or scavenged by rivers and ponds. Small amphibians probably provided meals, and perhaps the freshwater shark Xenacanthus did too. Xenacanthus preyed in turn on fishes, reptiles, amphibians, and perhaps an unwary Dimetrodon.


  • Title: Pelycosaur synapsid (composite)
  • Location: Arroyo Formation, Baylor Co., Texas, United States, North America
  • Physical Dimensions: L: 315 cm W: 86 cm H: 147 cm
  • Type: Fossil
  • Rights: This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws. http://www.si.edu/termsofuse
  • External Link: View this object record in the Smithsonian Institution Collections Search Center
  • Weight: 200 kg (estimated)
  • USNM Catalog Number(s): V8635, V8661, and others
  • Scientific Name: <i>Dimetrodon grandis</i>
  • Photo Credit: James Di Loreto, Smithsonian Institution National Museum of Natural History
  • Historic Period: Lived 279–272 million years ago
  • Geologic Age: Paleozoic - Permian - Lower/Early
  • Field: Paleobiology
  • Date Collected: 1917

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