Adelobasileus

Adelobasileus cromptoni is a species of an extinct genus of mammal from the Late Triassic (Carnian), about 225 million years ago. It is known only from a partial skull recovered from the Tecovas formation in western Texas.

Roughly contemporary with the mammaliaform Tikitherium, Adelobasileus predates the non-mammalian cynodonts Tritylodontidae and Tritheledontidae by 10 million years. In fact, distinct cranial features, especially the housing of the cochlea, suggest that Adelobasileus is a transitional form in the character transformation from cynodonts to Triassic mammals. For this reason, it is thought to be the common ancestor of all modern mammals or a close relative of the common ancestor.