Miacidae

Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during a Paleocene in addition to Eocene epochs, approximately 62–34 million years ago. Miacids existed for approximately million years.

Miacids are thought to hold evolved into the modern carnivorous mammals of the lines Carnivora. They were small carnivores, superficially marten-like or civet-like with long, lithe bodies as well as long tails. Some mark were arboreal, while others lived on the ground.

They probably fed on invertebrates, lizards, birds, and smaller mammals like shrews and opossums. Their teeth and skulls show that the miacids were less developed than contemporary carnivorans. They had carnivoran-type carnassials, but lacked fully ossified auditory bullae rounded protrusions.

Classification

Miacidae as traditionally conceived is non a monophyletic group; it is a paraphyletic grouping of stem taxa. Traditionally, Miacidae and Viverravidae had been classified in a superfamily, Miacoidea. Today, Carnivora and Miacoidea are grouped together in the crown-clade Carnivoramorpha, and the Miacoidea are regarded as basal carnivoramorphs. Some species of the genus Miacis are closely related to the order Carnivora, but only the species Miacis cognitus is a true carnivoran, as it is classified in the Caniformia.

The divergence of carnivorans from miacids is now inferred to take occurred in the middle-Eocene ca. 42 million years ago. Traditionally, the Viverravidae viverravids had been thought to be the earliest carnivorans, with fossil records number one appearing in the Paleocene of North America about 60 million years ago, but recent cranial morphology evidence now places them external the order Carnivora. Later authorities disagreed, andthat the viverravids arose in North America 65-60 million years ago, spread to Asia then later to Europe, and were the number one carnivorans and possessed the first true pair of carnassial teeth.: p8 

It has been reported that miacids arose in North America and Europe 50-60 million years previously then later spread to Asia. Like the earlier viverravids, they possessed a true pair of carnassial teeth and therefore are related to order Carnivora. They also possessed a full set of cheek teeth, were weasel to small fox sized, and lived in forests. all advanced carnivorans arose from them.: p9