Miacids Fossil range: Late Paleocene - Early Eocene
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
(unranked):	Carnivoramorpha
Superfamily:	Miacoidea
Family:	Miacidae Cope, 1880
Genera
See text.

The miacids (Miacidae) were primitive carnivores which lived during the Paleocene and Eocene Epoch about 65—33 million years ago. Miacids existed for approximately 32 million years.

Miacids are thought to have evolved into today's modern carnivorous mammals of the order Carnivora. They were small marten-like carnivores with long, little bodies and long tails. Some species 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 the modern carnivores. They had Carnivora type carnassials but lacked fully ossified auditory bullae (rounded protrusions). They resembled Cimolestes, and this suggests that the order Carnivora evolved from a group of insectivores, related to Ungulates.

The miacids are divided into two groups: the miacines with a full complement of molars and the viverravines with a reduced number of molars and more specialized carnassials.

[edit] Classification

The Miacidae as traditionally conceived is not a monophyletic group; it is a paraphyletic array of stem taxa. Traditionally, the Miacidae and the Viverravidae had been classified in a third, extinct paraphyletic superfamily, the Miacoidea, from which the direct ancestors of both Carnivora and Creodonta were thought to have arisen. 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 evolved into modern day carnivores of the Order Carnivora, but only the species Miacis cognitus is a true carnivoran. Thus, Miacis may have given rise to all modern Carnivora.

The transition from Miacidae to Carnivora was a general trend in the middle and late Eocene with taxa from both North America and Eurasia involved. The divergence of carnivorans from other miacids is now inferred to be the middle-Eocene (ca. 42 million years ago). Traditionally the Viverravidae (viverravids) had been thought to be the earliest carnivorans with fossil records first appearing in the Paleocene of North America about 60 million years ago, but recent cranial morphology evidence now places them outside the order Carnivora.^[1]

[edit] Taxonomy

• Family Miacidae†
  • Genus Chailicyon
  • Genus Eosictis
  • Genus Ictognathus
  • Genus Messelogale^[2]
  • Genus Miacis
  • Genus Miocyon
  • Genus Oödectes
  • Genus Palaearctonyx
  • Genus Paramiacis
  • Genus Paroodectes
  • Genus Procynodictis^[3]
  • Genus Prodaphaenus
  • Genus Quercygale^[4]
  • Genus Tapocyon
  • Genus Uintacyon
  • Genus Vassacyon
  • Genus Vulpavus
  • Genus Xinyuictis
  • Genus Ziphacodon

[edit] References