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Former order of extinct flesh eating placental mammals

Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ancestral to the modern Carnivora, this order is now usually considered a polyphyletic assemblage of two different groups, the Oxyaenids and the Hyenodonts, not a natural group. Oxyaenids are first known from the Palaeocene of North America, while hyaenodonts hail from the Palaeocene of Africa. Creodonts were the dominant carnivorous mammals from , peaking in diversity and prevalence during the Eocene. The first large, obviously carnivorous mammals appeared with the radiation of the oxyaenids in the late Paleocene. In Oligocene Africa, hyaenodonts were the dominant group of large flesh eaters, persisting until the middle of the Miocene. "Creodont" groups had an extensive range, both geographically and temporally. They are known from the late Paleocene through the late Oligocene in North America, the early Eocene through late Oligocene in Europe, from the late Paleocene through late Miocene in Asia, and from the late Paleocene to the late Miocene in Africa. "Creodonts" share with the Carnivora, and many other predatory mammal clades, the carnassial shear, a scissors like modification of upper and lower cheek teeth that was used to slice muscle tissue. This adaptation is also seen in other clades of predatory mammals.

Early creodonts (both oxyaenids and hyaenodontids) displayed the tribosphenic molars common for basal therians. Small forms had somewhat strong postmetacrista metastellar crests suggesting that they were probably opportunistic feeders, eating such things as eggs, birds, small mammals, insects and possibly plant matter as well, possibly like extant viverrids. Larger forms had greater shearing capacity and the capacity increased over time. Arfia, one of the most common carnivorous mammals in early Eocene North America, developed a more open trigonid on M3 over the course of the Early Eocene, increasing the shearing ability of the carnassials. A similar development can be seen by comparing Oxyaena, Prototomus and Limnocyon with the smaller, more generalized feeders among the creodonts.

Several theories have suggested that hyaenodonts and oxyaenids became extinct because they were outcompeted by the newly evolved Carnivora. However, there is no direct evidence that the existence of large Carnivora caused the extinction of these taxa, and in many cases (in Africa throughout the Early and Middle Miocene, and in North America and Eurasia during much of the Oligocene), hyaenodonts thrived in environments in which large carnivorans such as nimravids and (later) larger amphicyonids were also present as competitors. Theories that suggest they were outcompeted by the Carnivora include that their smaller brains limited their intelligence, but carnivoran brain sizes have not always been consistently large throughout their evolution, and the importance of brain size as a factor in intelligence has been vastly overestimated in the past when these ideas were published. Other speculations focus on their limb structure, which limited leg movement to a vertical plane, as in ungulates; they were unable to turn their wrists and forearms inward to trip, slash, or grab prey as some modern carnivores can. Creodonts had to depend entirely on their jaws to capture prey, which may be why creodonts generally had a larger head size in relation to their bodies than carnivores of similar stature. However, many carnivorans, such as large canids, are also dependent on their jaws alone to capture prey yet do so effectively even in situations where they must tackle large prey alone, so this also fails to provide a satisfactory explanation. In the Carnivora, the last upper premolar and the first lower molar are the carnassials, allowing the rearmost molar teeth to evolve adaptations for feeding on non meat foods. In creodonts, either the first upper and second lower molars, or the second upper and third lower molars, were the primary carnassials, and the rear teeth formed a carnassial series. This structure committed them to eating meat almost exclusively, which may have limited their ability to exploit mesocarnivore and omnivore ecological niches. These differences may have caused environmental changes to affect hyaenodonts and oxyaenids differently than they did many carnivorans, as the former would have been restricted to largely or entirely faunivorous diets, while many (though not all) carnivoran lineages were/are able to subsist on plant matter as well.