Miacids
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| Miacids Fossil range: Early Paleocene - Late Eocene |
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The miacids (Miacidae) were primitive carnivores which lived during the Paleocene and Eocene Epoch about 65 - 33 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.
[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 be considered the genus of carnivorous mammals that gave rise to all modern Carnivora.[citation needed]
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] Some paleontologists consider the viverravids to be ancestral to the aeluroid carnivorans (felids, hyaenids, herpestids and viverrids), but this is now doubted.[citation needed]
[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
- ^ Polly, David, Gina D. Wesley-Hunt, Ronald E. Heinrich, Graham Davis and Peter Houde (2006). "Earliest Known Carnivoran Auditory Bulla and Support for a Recent Origin of Crown-Clade Carnivora (Eutheria, Mammalia)". Palaeontology 49 (5): 1019–1027. doi:.
- ^ Morlo, M.; Schaal, S.; Mayr, G.; Seiffert, C. (2004). "An annotated taxonomic list of the Middle Eocene (MP11) Vertebrata of Messel". Courier Forschungsinstitut Senckenberg 252: 95–108.
- ^ Wesley, G.D.; Flynn, J.J. (2003). "A revision Of Tapocyon (Carnivoramorpha), including analysis of the first cranial specimens and identification of a new species". Journal of Paleontology 77 (4): 769–783. doi:.
- ^ Wesley-Hunt, G.D.; Werdelin, L. (2005). "Basicranial morphology and phylogenetic position of the upper Eocene carnivoramorphan Quercygale". Acta Palaeontologica Polonica 50 (4): 837–846.
