''Miacis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of extinct carnivorous mammals that appeared in the late

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

and continued through the

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

. The genus ''Miacis'' is not

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

but a diverse collection of species that belong to the stemgroup within the

Carnivoramorpha Carnivoramorpha ("carnivoran-like forms") is a clade of placental mammals that includes the modern order Carnivora and its extinct stem-relatives.Bryant, H.N., and M. Wolson (2004“Phylogenetic Nomenclature of Carnivoran Mammals.”''First Inter ...

.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 Carnivora is a Clade, monophyletic order of Placentalia, placental mammals consisting of the most recent common ancestor of all felidae, cat-like and canidae, dog-like animals, and all descendants of that ancestor. Members of this group are f ...

. However, the species ''

Miacis cognitus ''Gustafsonia'' is an extinct genus of carnivoran belonging to the family Amphicyonidae (a bear dog). The type species, ''Gustafsonia cognita'', was described in 1986 by Eric Paul Gustafson, who originally interpreted it as a miacid and named i ...

'' (now ''Gustafsonia'') is placed not in the stem-group but among the

Caniformia Caniformia is a suborder within the order Carnivora consisting of "dog-like" carnivorans. They include dogs (wolves, foxes, etc.), bears, raccoons, and mustelids. The Pinnipedia (seals, walruses and sea lions) are also assigned to this group. ...

,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

. ''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 bo ...

(~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 The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

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

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s, 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 lightweigh ...

s, and might also have eaten eggs and fruits.

Taxonomy

Since

Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested ...

first described the genus ''Miacis'' in 1872, at least twenty other species have been assigned to ''Miacis''. However, these species share few

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

other than

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, and ...

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