Estemmensuchus is a synapsid confirmed to appear in Additional Creatures 2: Wild ARK.
Estemmenosuchus, meaning "Crowned Crocodile" lived in Russia during the Late Permian: 260 million years ago. It was an omnivorous relative of the Moschops, but looked quite a bit different thanks to the unique set of "crowns" that adorned its head. These were likely for display, as females had a different set compared to the males. This look makes it one of the most unique-looking creatures of the Permian.
It is unknown what role Estemmenosuchus will play in Additional Creatures, but it is confirmed to be inspired by the old concept of Estemmenosuchus that the mod developer created for ARK in a dossier, which labelled it as a primarily desert creature that was notable for being a generalist, being able to be used for combat, weight, and other forms of utility.