Miacids are

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

primitive carnivoramorphans within the family Miacidae that lived during the

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

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' ...

epochs, about 62–34 million years ago. Miacids existed for approximately . Miacids are thought to have evolved into the modern carnivorous

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 ...

s of the order

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 ...

. They were small carnivores, superficially

marten A marten is a weasel-like mammal in the genus ''Martes'' within the subfamily Guloninae, in the family Mustelidae. They have bushy tails and large paws with partially retractile claws. The fur varies from yellowish to dark brown, depending on t ...

-like or

civet A civet () is a small, lean, mostly nocturnal mammal native to tropical Asia and Africa, especially the tropical forests. The term civet applies to over a dozen different species, mostly from the family Viverridae. Most of the species diversity ...

-like with long, lithe bodies and long tails. Some species were

arboreal Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...

, while others lived on the ground. They probably fed on invertebrates,

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

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 smaller

s like

shrew Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different fa ...

s and

opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 93 species in 18 genera. Opossums originated in South America and entered North ...

s. Their

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

and

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

s show that the miacids were less developed than modern carnivorans. They had carnivoran-type

carnassials Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...

, but lacked fully

ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by Cell (biology), cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes ...

auditory bullae (rounded protrusions).

Classification

Miacidae as traditionally conceived is not a

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 ...

group; it is a

paraphyletic In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...

array of stem

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

. Traditionally, Miacidae and

Viverravidae Viverravidae ("ancestors of viverrids") is an extinct monophyletic family of mammals from extinct superfamily Viverravoidea within the clade Carnivoramorpha, that lived from the early Palaeocene to the late Eocene in North America, Europe and As ...

had been classified in a superfamily,

Miacoidea Miacoidea ("small points") is a former paraphyletic superfamily of extinct placental mammals that lived during the Paleocene and Eocene epochs, about 66-33,9 million years ago.K. D. Rose, A. E. Chew, R. H. Dunn, M. J. Kraus, H. C. Fricke and S. ...

. 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 ''Miacis'' is a genus of extinct carnivorous mammals that appeared in the late Paleocene and continued through the Eocene. The genus ''Miacis'' is not monophyletic but a diverse collection of species that belong to the stemgroup within the Ca ...

'' are closely related to the order Carnivora, but only the species ''Miacis cognitus'' is a true carnivoran, as it is classified in 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. ...

. The divergence of carnivorans from miacids is now inferred to have occurred in the middle-Eocene (ca. 42 million years ago). Traditionally, the

(viverravids) had been thought to be the earliest carnivorans, with fossil records first appearing in the Paleocene of

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

about 60 million years ago, but recent cranial

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

evidence now places them outside the order Carnivora. Later authorities disagreed, and propose that the viverravids arose in North America 65-60 million years ago, spread to Asia then later to Europe, and were the first carnivorans and possessed the first true pair of

carnassial Carnassials are paired upper and lower teeth modified in such a way as to allow enlarged and often self-sharpening edges to pass by each other in a shearing manner. This adaptation is found in carnivorans, where the carnassials are the modified f ...

teeth. It has been proposed that miacids arose in North America and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

50-60 million years ago then later spread to Asia. Like the earlier

viverravids Viverravidae ("ancestors of viverrids") is an extinct monophyletic family of mammals from extinct superfamily Viverravoidea within the clade Carnivoramorpha, that lived from the early Palaeocene to the late Eocene in North America, Europe a ...

, they possessed a true pair of

teeth and therefore are related to order Carnivora. They also possessed a full set of cheek teeth, were weasel to small fox sized, and lived in

forest A forest is an area of land dominated by trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, and ecological function. The United Nations' ...

s. All modern carnivorans arose from them.

Taxonomy

*Family Miacidae† **Genus ''

Eosictis ''Eosictis'' is an extinct genus of Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids existed for approximately ...

'' **Genus ''

Messelogale ''Messelogale'' is an extinct genus of Miacidae. Its fossils have been found in Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and ...

'' **Genus ''

Miocyon ''Miocyon'' is an extinct genus of Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids existed for approximately . ...

'' **Genus ''

Oodectes ''Oodectes'' is an extinct genus of Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids existed for approximately ...

'' **Genus ''

Palaearctonyx ''Palaearctonyx'' is an extinct genus of omnivorous Miacidae which inhabited North America during 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 ...

'' **Genus ''

Paramiacis ''Paramiacis'' is an extinct genus of Miacidae. Christian Mathis has defined to make a difference between the miacids from Europe and the American genus ''Miacis''. There are two species of it, ''P. exilis'' (Henri Filhol, 1876) and ''P. teilhard ...

'' **Genus ''

Paroodectes ''Paroodectes'' is a miacid animal that lived during the early Eocene (ca. 50 million years ago) in the rain forests and swamps of the present-day Germany. It was a prehistoric predator that had the size and the appearance of a cat and was well ...

'' **Genus '' Procynodictis'' **Genus ''

Prodaphaenus ''Prodaphaenus'' is an extinct genus of Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids existed for approxima ...

'' **Genus ''

Quercygale ''Quercygale'' is an extinct genus of Miacidae, primitive carnivores that lived during the Eocene. The genus contains four species: ''Q. angustidens'', ''Q. hastingsae'', ''Q. helvetica'', and ''Q. smithi''. Phylogenetic analysis of the basicran ...

'' **Genus ''

Tapocyon ''Tapocyon'' ("dog from Tapo Canyon") is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America during the middle Eocene.J. J. Flynn (1998.) "Early Cenozoic Carnivora ("Miacoidea")." In C. M. Janis, K. M ...

'' **Genus ''

Uintacyon ''Uintacyon'' is an extinct genus of Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids existed for approximately ...

'' **Genus ''

Vassacyon ''Vassacyon'' is an extinct genus of Miacidae. It contains two species; ''Vassacyon promicrodon'' and ''Vassacyon bowni''. It is considered the largest of the early Eocene mammals Mammals () are a group of vertebrate animals constitut ...

'' **Genus ''

Vulpavus ''Vulpavus'' ("fox grandfather") is an extinct genus of Miacidae Miacids are extinct primitive carnivoramorphans within the family Miacidae that lived during the Paleocene and Eocene epochs, about 62–34 million years ago. Miacids exist ...

'' **Genus ''

Xinyuictis Xinyuictis is an extinct genus of Miacidae. It contains a species, ''Xinyuictis tenuis''. It was once suggested that the species was the same as ''Miacis ''Miacis'' is a genus of extinct carnivorous mammals that appeared in the late Paleoc ...

References

{{Taxonbar, from=Q2020380 Obsolete mammal taxa Paleocene first appearances Eocene extinctions Prehistoric mammal families