Pelycosaur synapsid (composite)

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.

HUNTING IN THE RIVERS

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.