''Miacis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of extinct carnivorous mammals that appeared in the late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

and continued through the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

. The genus ''Miacis'' is not monophyletic but a diverse collection of species that belong to the stemgroup within the Carnivoramorpha.Wesley-Hunt, G.D.; Flynn J.J. (2005). Phylogeny of the Carnivora: Basal Relationships Among the Carnivoramorphans, and Assessment of the Position of 'Miacoidea' Relative to Carnivora. ''Journal of Systematic Palaeontology'', 3: 1-28. As such, most ''Miacis'' species belong to the group of early carnivores that represent the ancestors of the modern order, the

crown-group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...

Carnivora. However, the species '' Miacis cognitus'' (now ''Gustafsonia'') is placed not in the stem-group but among the Caniformia,Spaulding, M.; Flynn J.J.; Stucky, R.K. (2010) Anew basal Carnivoramorphan (Mammalia) from the ‘Bridger B’ (Black’s Fork Member, Bridger Formation, Bridgerian NALMA, Middel Eocene) of Wyoming, USA. ''Paleontology'' 53: 815-832. one of the two suborders of the

Carnivora. ''Miacis'' species were five-clawed, about the size of a

weasel Weasels are mammals of the genus ''Mustela'' of the family Mustelidae. The genus ''Mustela'' includes the least weasels, polecats, stoats, ferrets and European mink. Members of this genus are small, active predators, with long and slender b ...

(~30 cm), and lived on the North American and Eurasian continents. They retained some primitive characteristics such as low skulls, long slender bodies, long tails, and short legs. ''Miacis'' retained 44 teeth, although some reductions in this number were apparently in progress and some of the teeth were reduced in size. The hind limbs were longer than the forelimbs, the pelvis was dog-like in form and structure, and some specialized traits were present in the vertebrae. It had retractable claws, agile joints for climbing, and

binocular vision In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...

. ''Miacis'' and related forms had brains that were relatively larger than those of the

creodont Creodonta ("meat teeth") is a former order of extinct carnivorous placental mammals that lived from the early Paleocene to the late Miocene epochs in North America, Europe, Asia and Africa. Originally thought to be a single group of animals ance ...

s, and the larger brain size as compared with body size probably reflects an increase in intelligence. Like many other early carnivoramorphans, it was well suited for an arboreal climbing lifestyle with needle sharp claws, and had limbs and joints that resemble those of modern carnivorans. ''Miacis'' was probably a very agile forest dweller that preyed upon smaller animals, such as small mammals, reptiles, and

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and might also have eaten eggs and fruits.

Taxonomy

Since Edward Drinker Cope first described the genus ''Miacis'' in 1872, at least twenty other species have been assigned to ''Miacis''. However, these species share few synapomorphies other than plesiomorphic characteristics of miacids in general. This reflects the fact that ''Miacis'' has been treated as a wastebasket taxon and contains a diverse collection of species that belong to the stemgroup within the Carnivoramorpha. Many of the species originally assigned to ''Miacis'' have since been assigned to other genera and, apart from the type species, ''Miacis parvivorus'', the remaining species are often referred to with ''Miacis'' in quotations (e.g. ''"Miacis" latidens''). The following table lists the ''Miacis species'' in chronological order of their original description and notes the reassignments to other genera.

Phylogeny

A phylogenetic analysis of "Miacis" species and other carnivoramorphans reveals the paraphyletic nature of the genus ''Miacis''. Some are found in a basal position among the stem carnivoraform groups, others are clustered in the middle near ''Miacis parvivorous'', and one, ''"M". cognitus'', within Caniform family Amphicyonidae. The cladogram is based on a morphological analysis of dental, cranial, and postcranial features.

In popular culture

In the episode "Mungu's Revenge", of the 1990s TV nature program ''Kratts' Creatures'', Ttark says, "Now, did I ever tell you about that furry little ''Miacis'' of the late Paleocene period...or was that the early Eocene?".

References

External links

* * {{Taxonbar, from=Q133030 † Paleocene mammals of North America Eocene mammals of North America Prehistoric placental genera Miacids Eocene carnivorans Transitional fossils Paleocene carnivorans Fossil taxa described in 1872