The Malevolusaurus (Malevolusaurus perditor) is a large, omnivorous sphenacodontine sphenacodontid from the uplands of Skull Island, descended from Dimetrodon. It measures 20-24 feet long.
Pugnacious and ill-tempered, the burly Malevolusaurus is an opportunistic omnivorous pelycosaur of the highlands. It scavenges carrion or steals wounded live prey from other predators, digs smaller animals from burrows, and uproots plants for their roots and tubers. It will also go after such prey that is difficult to catch like dracos.
The distinctive sails, an heirloom of Permian ancestry, are an adaptation Malevolusaurus employ to warm themselves in the morning, boosting their energy levels for the day. Many are badly torn or otherwise scarred, a result of dominance battles between the fiercely territorial creatures. Males have knobby “crowns” with which they will butt one another, but biting and clawing are common.
Malevolusaurus lay their eggs in scrapes on the sunniest slopes where they will be naturally warmed. The greatest threat to newly hatched young comes from their own kind (80 percent of young fall prey to hungry adults in their first year). This cannibalism is strangely an effective population control, as little else eats them. Only the saber-toothed Gladiodon hunts full-grown Malevolusaurus.