The Carnivora, as represented by the (mainly) Eocene Creodonta, are evidently an ancient and generalized type.
Another view is to regard both marsupials and placentals as derivates from implacental ancestors more or less nearly related to the creodont carnivora, or possibly as independently descended from anomodont reptiles (see Creodonta).
The alleged occurrence in the same beds of marsupials allied to the thylacine is based on remains now more generally regarded as referable to the creodont carnivores (see Creodonta).
They are, however, more probably members of the creodont Carnivora (see Creodonta).
The skull was small, with proportionately minute brain; and the arched back, strong lumbar vertebrae, long and powerful tail, and comparatively feeble fore-quarters all proclaim kinship with the primitive creodont Carnivora (see Creodonta), from which Phenacodus and its allies, and through them the more typical Ungulata, are probably derived.