Like other non-mammalian therapsids , therocephalians are sometimes described as mammal-like reptiles . In fact Therocephalia is the group most closely related to the cynodonts , which gave rise to the mammals . Like other non-mammalian synapsids , therocephalians are described as mammal-like reptiles , although in fact , Therocephalia is the group most closely related to the cynodonts , which gave rise to the mammals .