Cotylorhynchus is a synapsid confirmed to appear in Additional Creatures: Endemics.
Cotylorhynchus, meaning "Cup Snout", is a species of giant stem-mammal that lived in southwest North America during the Early Permian, 280 million years ago. This animal shared its habit with other animals like Diplocaulus, Edaphosaurus, and Dimetrodon. Cotylorhynchus stands out for its time in a few key ways. It was not only one of the planet's first large terrestrial herbivores, but it also took this to the extreme. At 6 meters long, it was one of the largest land animals of its time, and was likely immune to predation when adults. It is also one of the first large-bodied stem-mammals. Cotylorhynchus in particular is also well known for its bizarre body shape, having a ridiculously huge gut proportionally, along with a tiny head for its body size. This barrel-like body and limb structure could suggest aquatic tendencies, but this is largely speculative.
Cotylorhynchus is confirmed to appear in Additional Creatures with the model created by Jagged Fang Designs. It is known that this creature will be able to help with creating "alchemy and potions" although exactly what this means can be up for debate.