Palaeonictis

Tooth of Phenacodus and Palaeonictis

In life, it would have resembled a large modern wolverine. This oxyaenid had heavy jaws and blunt robust teeth more suited for crushing bones, than slicing meat. This meant that the plantigrade Palaeonictis was at least a part-time scavenger. The biggest species, Palaeonictis peloria (meaning "terrible ancient weasel") is known from an incomplete jaw that must have measured over 20 centimetres (7.9 in) in length. This animal was the largest carnivore in its ecosystem. 55 million years ago, P. occidentalis (the size of a bear) evolved into the smaller P. wingi (the size of a coyote) within 200,000 years in the early Eocene due to global warming (paleoclimatology). By the end of the middle Eocene (38 million years ago), Palaeonictis disappeared from North America, and by the late Eocene (34 million years ago) the last species of P. gigantea had vanished from Europe.[2] In fact, the entire family Oxyaenidae had become extinct worldwide (although its sister group Hyaenodontidae continued to thrive for a while). This is traditionally assumed to be due to increased competition from miacids and nimravids belonging to the more successful order Carnivora, which eventually replaced earlier carnivorous mammal clades in the later Neogene as the world's top predators, though no evidence of direct competition is known, and carnivorans may have simply filled vacated niches.