MIACIDS

The 'miacids' ''(Miacidae)'' were primitive carnivores which lived during the Paleocene and Eocene Epoch about 33-65 million years ago. Miacids are thought to have evolved into todays modern carnivorous mammals of the order Carnivora.
The miacids were small marten-like carnivores with long, little bodies, and long tails. Some species were arboreal, others lived on the ground. They probably fed on invertebrates, lizards, birds and smaller mammals like shrews and opossums. Their teeth and skull show that the miacids were less developed than the modern carnivores. They had Carnivora type carnassials but lacked fully ossified auditory bulla (a rounded protrusion). 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 carnnassials.

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Classification

References

Classification

The Miacidae 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 arose. Today, Carnivora and Miacoidea are grouped together in the crown-clade Carnivoramorpha, and the Miacoidae 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 Carnivora. Thus, Miacis may be considered the genus of carnivorous mammals that gave 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. Earliest Known Carnivoran Auditory Bulla and Support for a Recent Origin of Crown-Clade Carnivora (Eutheria, Mammalia), Polly, David, Gina D. Wesley-Hunt, Ronald E. Heinrich, Graham Davis and Peter Houde, , , Palaeontology, 2006 Some paleontologists consider the viverravids to be ancestral to the aeluroid carnivorans (felids, hyaenids, herpestids and viverrids, but this is now doubted.
Superfamily Miacoidea†

★ Family Miacidae

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★ genera: ''Chailicyon'', ''Eostictis'', ''Ictognathus'', ''Miacis'', ''Miocyon'', ''Oodectes'', ''Palaearctonyx'', ''Paramiacis'', ''Paroodectes'', ''Prodaphaenus'', ''Tapocyon'', ''Uintacyon'', ''Vassacyon'', ''Vulpavus'', ''Xinyuictis'', ''Ziphacodon''

★ Family Viverravidae

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★ genera: ''Bryanictis'', ''Didymictis'', ''Ictidopappus'', ''Intyrictis'', ''Mustelodon'', ''Pristinictis'', ''Protictis'', ''Raphictis'', ''Simpsonictis'', ''Viverravus'', ''Quercygale''

References