One view of the position of the group is that Creodonta and Carnivora are sister taxa (within a superorder Ferae). Others have argued that insectivorans are more closely related to carnivorans, and creodonts, therefore, are basal eutherians. Others have suggested that Creodonta might not be monophyletic. Polly has argued that the only available synapomorphy between oxyaenids and hyaenodontids is a large metastylar blade on the first molar (M1), but he believes that that feature is common for all basal eutheria. Separating Oxyaenidae from Hyaenodontidae would also comport with biogeographic evidence, since the first oxyaenid is known from the North American early Paleocene and the first hyaenodontids are from very late Paleocene of North Africa.