Miacoidea is an extinct paraphyletic superfamily that has been traditionally divided into two families of carnivores: Miacidae (the miacids) and Viverravidae. They were primitive carnivores which lived during the Paleocene and Eocene Epoch about 33-65 million years ago. Today, Miacoidea is recognized as a paraphyletic array of stem taxa that probably resulted in some "miacoid" genera ending up just outside the order Carnivora. For this reason, Miacoidea are now grouped together in the crown clade Carnivoramorpha. Carnivoramorpha consists of both Miacoidea and Carnivora, but excludes the order Creodonta that evolved later alongside Carnivora. Miacoids are regarded as basal carnivoramorphs. The miacids may also be a paraphyletic family.
The transition from Miacoidea (miacoids) to Miacidae (miacids) to Caniform Carnivora, and Viverravidae to Feliform Carnivora, was a gradually trend during the Paleocene to late Eocene, with taxa from both North America and Eurasia involved. Cladistic analysis shows that different Miacoids evolved into different lineages of Carnivora. Viverravidae are related to Feliformes on the basis of a reduction of the number of molars to two, and an enlongated skull. The miacids, however, did not appear until the very end of the Paleocene and are characterized by their shorter skull, and loss of contact between the calcaneum and fibula in the ankle. These two main lineages of modern Carnivora can be traced back to the Early Paleocene by fossil evidence. The Miacidae (miacids) evolved into the modern Caniformes (dogs, bears, raccoons and weasels), while the Viverravidae evolved into the Feliformes (cats, hyaenas and mongooses), both of the order Carnivora.
Miacoids were mostly small marten-like carnivores. They probably fed on invertebrates, lizards, birds and smaller mammals like shrews and opossums, while others may have been insectivores. Some species were arboreal, others lived on the ground. Their teeth and skull show that the miacoids were less developed than modern carnivores.
New Viverravids from the Torrejonian (middle Paleocene) of Kutz Canyon, New Mexico and the oldest skull of the Order Carnivora
Nov 01, 2002; ABSTRACT-Three new species of Viverravidae (Carnivora: Miacoidea) are described: Protictis simpsoni, P. minor, and...