Gordodon

Gordodon (meaning "fat tooth", referring to its large incisor-like front teeth) is an extinct genus of non-mammalian synapsid that lived during the Early Permian of what is now Otero County, New Mexico. It was a member of the herbivorous sail-backed family Edaphosauridae and contains only a single species, the type species G. kraineri. Gordodon is unusual among early synapsids for its teeth, which were arranged similarly to those of modern mammals and unlike the simple, uniform lizard-like teeth of other early herbivorous synapsids. Gordodon had large incisor-like teeth at the front, followed by a prominent gap between them and a short row of peg-like teeth at the back. Gordodon was also relatively long-necked for an early synapsid, with elongated and gracile vertebrae in its neck and back. Like other edaphosaurids, Gordodon had a tall sail on its back made from the bony neural spines of its vertebrae. The spines also had bony knobs on them, a common trait of edaphosaurids, but the knobs of Gordodon are also unique for being more slender, thornlike and randomly arranged along the spines. It is estimated to have been rather small at in length excluding the tail and in weight.

The unique jaws and teeth of Gordodon amongst early synapsids suggest that it was one of the first herbivorous tetrapods to have specialised in selectively feeding on high nutrient, low-fibre plant fructifications (seeds and fruit-like structures). It was also one of the first tetrapods to show such specialised dentition and feeding apparatus, evolving only a few million years after the first obligate tetrapod herbivores appeared in the fossil record. Prior to the discovery of Gordodon, the earliest non-mammalian synapsid herbivores with similarly complex teeth were the mammal-like cynodonts that appeared 95 million years later during the Triassic.