Miacids
Encyclopedia
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
and Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epochs about 62—33 million years ago. Miacids existed for approximately .
Miacids are thought to have evolved into today's modern carnivorous mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s of the order Carnivora
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
. They were small carnivores, superficially marten
Marten
The martens constitute the genus Martes within the subfamily Mustelinae, in family Mustelidae.-Description:Martens are slender, agile animals, adapted to living in taigas, and are found in coniferous and northern deciduous forests across the northern hemisphere. They have bushy tails, and large...
-like or civet
Civet
The family Viverridae is made up of around 30 species of medium-sized mammal, including all of the genets, the binturong, most of the civets, and the two African linsangs....
-like with long, little bodies and long tails. Some species were arboreal while others lived on the ground
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
.
They probably fed on invertebrates, lizard
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
s, bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s, and smaller mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s like shrew
Shrew
A shrew or shrew mouse is a small molelike mammal classified in the order Soricomorpha. True shrews are also not to be confused with West Indies shrews, treeshrews, otter shrews, or elephant shrews, which belong to different families or orders.Although its external appearance is generally that of...
s and opossums. Their teeth and skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
s show that the miacids were less developed than modern carnivorans. They had carnivoran-type carnassials but lacked fully ossified auditory
Cochlea
The cochlea is the auditory portion of the inner ear. It is a spiral-shaped cavity in the bony labyrinth, making 2.5 turns around its axis, the modiolus....
bullae (rounded protrusions).
Classification
Miacidae as traditionally conceived is not a monophyletic group; it is a paraphyletic array of stem taxa. Traditionally, Miacidae and Viverravidae had been classified in a superfamily, MiacoideaMiacoidea
Miacoidea is paraphyletic superfamily that had been traditionally divided into two families of carnivores: Miacidae and Viverravidae. Miacoids were primitive carnivores which lived during the Paleocene and Eocene Epoch about 33-65 million years ago...
. Today, Carnivora and Miacoidea are grouped together in the crown-clade Carnivoramorpha
Carnivoramorpha
Carnivoramorpha are a clade of mammals that includes the modern order Carnivora and its closest extinct relatives in the Miacoidea , but excludes the creodonts. The order Creodonta are a sister taxon to the Carnivoramorpha dating back 58.7 million years ago...
, and the Miacoidea are regarded as basal carnivoramorphs. Some species of the genus Miacis
Miacis
The 'genus' Miacis contains extinct species of 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 Carnivoramorpha...
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
Caniformia, or Canoidea , is a suborder within the order Carnivora. They typically possess a long snout and non-retractile claws . The Pinnipedia evolved from caniform ancestors and are accordingly assigned to this group...
.
The transition from miacids 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 miacids is now inferred to have occurred in 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
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
evidence now places them outside the order Carnivora.
Taxonomy
- Family Miacidae†
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- Genus EosictisEosictisEosictis is an extinct genus of Miacidae. It was first named by Scott in 1945, and contains one species, Eosictis avinoffi.-Sources:**...
- Genus MesselogaleMesselogaleMesselogale is an extinct genus of Miacidae. Its fossils have been found in Europe. There is one assigned species: M. kessleri.-Sources:**...
- Genus MiacisMiacisThe 'genus' Miacis contains extinct species of 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 Carnivoramorpha...
- Genus MiocyonMiocyonMiocyon is an extinct genus of Miacidae, primitive carnivores which lived during the Paleocene and Eocene Epoch.-References:* Flynn, J.J., 1998. Early Cenozoic Carnivora . pp.110-123 in C.M. Janis, K.M. Scott, and L.L. Jacobs Evolution of Tertiary Mammals of North America...
- Genus OodectesOödectesOodectes is an extinct genus of Miacidae.-Sources:**Fossil Mammalia of the Huerfano Formation, Eocene, of Colorado by Peter Robinson**...
- Genus PalaearctonyxPalaearctonyxPalaearctonyx is an extinct genus of omnivorous Miacidae which inhabited North America during the Eocene living from 50.3—46.2 Ma and existed for approximately .-Taxonomy:Palaearctonyx was named by Matthew . Its type is Palaearctonyx meadi...
- Genus ParamiacisParamiacisParamiacis is an extinct genus of Miacidae. Christian Mathis has defined to make a difference between the miacidae from Europe and the American genus Miacis. There are two species of it, P. exilis and P...
- Genus ParoodectesParoodectesParoodectes was a miacid animal that lived during the early Eocene 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 adapted to climbing, as is apparent from its limbs, joints and shoulder bones...
- Genus ProcynodictisProcynodictisProcynodictis is an extinct genus of Miacidae. It was first named by Wortman and Matthew in 1899, and contains two species: P. progressus and P. vulpiceps. It was identified as an ancestor of Hesperocyon.-Sources:****...
- Genus ProdaphaenusProdaphaenusProdaphaenus is an extinct genus of Miacidae. The genus has at least one known species: Prodaphaenus scotti.-References:***...
- Genus QuercygaleQuercygaleQuercygale is an extinct genus of Miacidae, primitive carnivores that lived during the Paleocene and Eocene epochs. The genus contains three species: Q. angustidens , from Quercy , Q. hastingsae , from Headon Bedes, England and Q. helvetica, from Switzerland...
- Genus TapocyonTapocyonTapocyon is an extinct genus of Miacidae, a family of primitive carnivores. Tapocyon was first discovered in Ventura County, when part of a jaw was found in the 1930's. A representative fossil of Tapocyon robustus was found in Oceanside, California...
- Genus UintacyonUintacyonUintacyon is an extinct genus of Miacidae. There are at least two species in the genus; Uintacyon rudis and Uintacyon gingerichi, the latter being recently discovered.-Sources:...
- Genus VassacyonVassacyonVassacyon 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.-References:...
- Genus VulpavusVulpavusVulpavus is an extinct genus of Miacidae.-References:* Alexander, J. 1992. Alas poor Notharctus. Natural History 9:54-59.* Flynn, J.J., 1998. Early Cenozoic Carnivora . pp.110-123 in C.M. Janis, K.M. Scott, and L.L. Jacobs Evolution of Tertiary Mammals of North America...
- Genus XinyuictisXinyuictisXinyuictis is an extinct genus of Miacidae. It contains a species, Xinyuictis tenuis. It was once suggested that the species was the same as Miacis, but it was eventually decided that they were different.-Sources:...
- Genus ZiphacodonZiphacodonZiphacodon is an extinct genus of Miacidae. The species Ziphacodon rugatus was described as a new species by M. R. Thorpe in 1923. The genus itself was first described by Marsh in 1872.-Sources:...
- Genus Eosictis