sphenacodonts

Sphenacodonts were a successful group of therapsid amniotes that lived during the Permian period. They are often considered a basal group within the Synapsida, the lineage that would eventually lead to mammals. Sphenacodonts are characterized by a distinctive dentition, featuring large, recurved canine teeth and a gap, or diastema, between the incisors and canines, followed by rows of smaller postcanine teeth. Their skulls were generally robust, with a single temporal fenestra located behind the orbit, a defining feature of synapsids.

Fossil evidence suggests that sphenacodonts were primarily terrestrial carnivores, ranging in size from small, agile predators to larger, more powerful hunters. Some of the more well-known sphenacodonts include Dimetrodon, famous for its large sail-like structure on its back, and Sphenacodon. The function of the sail in Dimetrodon is still debated, with theories including thermoregulation, display, or a combination of both. Sphenacodonts diversified significantly throughout the Permian, occupying various ecological niches. Their evolutionary success paved the way for the further development of therapsids, which would go on to dominate terrestrial ecosystems in the Mesozoic Era. The extinction of many sphenacodont lineages coincided with the end-Permian mass extinction event.