Amphicyonidae is an

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 ...

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

of terrestrial

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 ...

ns belonging to the

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

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. T ...

. They first appeared in

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 th ...

in the middle

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'', ...

(around 45 mya), spread to

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 ...

by the late Eocene (35 mya), and appear in

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

, and

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

by the early

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

(23 mya). They had largely disappeared worldwide by the late Miocene (8 mya), with the latest recorded

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

at the end of the Miocene in

Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...

. They were among the first carnivorans to evolve large body size. Later in their history, they came into competition with hesperocyonine and borophagine canids. As dogs evolved similar body sizes and cranial and dental adaptations, the rise of these groups may have led to their extinction. Amphicyonids are often colloquially referred to as "bear-dogs".

Taxonomy

The family was erected by Haeckel (1886) lso attributed to Trouessart (1885) Their exact position has long been disputed. Some early paleontologists defined them as members of the family

Canidae Canidae (; from Latin, '' canis'', " dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found withi ...

, but the modern consensus is that they form their own family. Some researchers have defined it as the sister clade to ursids (

bear Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the No ...

s), based on morphological analysis of the ear region. However, cladistic analysis and reclassification of several species of early carnivore as amphicyonids has strongly suggested that they may be basal caniforms, from lineages older than the origin of both bears and dogs.Hunt, Robert M, Jr. (2004
"Global Climate and the Evolution of Large Mammalian Carnivores during the Later Cenozoic in North America"
in ''Cenozoic Carnivores and Global Climate'' by Robert M. Hunt, Jr. ''Bulletin of the American Museum of Natural History'' (285) 139-285

Description

Amphicyonids ranged in size from as small as and as large as and evolved from wolf-like to bear-like body forms. Early amphicyonids, such as ''

Daphoenodon ''Daphoenodon'' is an extinct genus of terrestrial carnivore, which lived in the early Miocene and belonged to the family Amphicyonidae ("bear dogs") of the suborder Caniformia Caniformia is a suborder within the order Carnivora consisti ...

'', possessed a

digitigrade In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the groun ...

posture and locomotion (walking on their toes), while many of the later and larger species were

plantigrade 151px, Portion of a human skeleton, showing plantigrade habit In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. ...

or semiplantigrade. The amphicyonids were obligate carnivores, unlike the Canidae, which are hypercarnivores or

mesocarnivore A mesocarnivore is an animal whose diet consists of 50–70% meat with the balance consisting of non-vertebrate foods which may include insects, fungi, fruits, other plant material and any food that is available to them. Mesocarnivores are from ...

s. There is often some confusion with the similar looking (and similarly named) "dog-bears", a more derived group of caniforms that is sometimes classified as a family (

Hemicyonidae Hemicyoninae is an extinct subfamily of Ursidae, often called dog bears (literally "half dog" (Greek: )). They were bear-like carnivorans living in Europe, North America, Africa and Asia during the Oligocene through Miocene epochs 33.9–5.3&n ...

), but is more often considered a primitive subfamily of ursids ( Hemicyoninae).

Evolution

It has long been uncertain where amphicyonids originated. It was thought that they may have crossed from Europe to North America during the

epoch, but recent research suggests a possible North American origin from the miacids ''Miacis cognitus'' and ''M. australis'' (now renamed as the

genera 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 nomenclat ...

'' Gustafsonia'' and '' Angelarctocyon'', respectively). As these are of North American origin, but appear to be early amphicyonids, it may be that the Amphicyonidae actually originates in North America.Tomiya S., and Tseng Z. J. 2016 Whence the beardogs? Reappraisal of the Middle to Late Eocene ‘Miacis’ from Texas, USA, and the origin of Amphicyonidae (Mammalia, Carnivora). Royal Society Open Science. DOI: 10.1098/rsos.160518 http://rsos.royalsocietypublishing.org/content/3/10/160518 Other New World amphicyonids include the oldest known amphicyonid, ''

Daphoenus ''Daphoenus'' is an extinct genus of bear dogs. ''Daphoenus'' inhabited North America from the Middle Eocene to the Middle Miocene, 37.2—16.0 Mya, existing for approximately . Species ''D. hartshornianus'' fossils found in Oligocene Orellan ...

'' (37–16 Mya). Amphicyonids began to decline in the late Miocene, and disappeared by the end of the epoch. The reasons for this are unclear; possibly it was due to competition with other carnivorans, as large canids had better adaptations to pursue swift prey in open country, a habitat which spread globally as the new grassland biome replaced more closed environments. However, no direct evidence for this idea has been found. The most recent known amphicyonid remains are teeth known from the Dhok Pathan horizon, northern

, dating to 7.4-5.3 mya. The species is classically named ''Arctamphicyon lydekkeri'', which may actually be synonymous with a species of ''

Amphicyon ''Amphicyon'' ("ambiguous dog") is an extinct genus of large carnivorous bone-crushing mammals, popularly known as bear dogs, of the family Amphicyonidae, subfamily Amphicyoninae, from the Burdigalian Epoch until the late Pliocene, with the cre ...

''. Fossils of juvenile ''

Agnotherium ''Agnotherium'' is a genus of large sized carnivoran mammals, belonging to the Amphicyonidae ("bear dogs"), which has been found in Western Europe, and possibly Northern Africa, and lived during the Late Miocene epoch. Despite only being known fr ...

'', ''

Ischyrocyon ''Ischyrocyon'' is an extinct genus of bear dogs, of the subfamily Amphicyoninae, which inhabited North America during the Late Miocene. It lived ~13.6—10.3 Ma ago, existing for approximately . Behavior In a study published in 2020, exam ...

'', and '' Magericyon'' all show an unusual type of tooth eruption in which there is a vulnerable stage at about two or three years of age where the subadult animal has no functional molar or carnassial teeth, the only functional cheek teeth being several milk premolars. This period was suggested to be "presumably short" but would have made it very difficult for the animal to process food. This type of tooth replacement is not seen in similar carnivorans like ursids or canids, and may have been one factor in the extinction of the Amphicyonidae.

Classification

* Family Amphicyonidae ** Genus '' Aktaucyon'' *** ''A. brachifacialis'' ** Genus ''

Amphicyanis ''Amphicyanis'' is an extinct genus of terrestrial carnivores belonging to the suborder Caniformia, family Amphicyonidae ("bear dog"), and which inhabited Eurasia and North America North America is a continent in the Northern Hemisph ...

'' ** Genus '' Angelarctocyon'' *** ''A. australis'' (formerly ''Miacis australis'') ** Genus '' Brachycyon'' *** ''B. reyi'' *** ''B. palaeolycos'' *** ''B. gaudryi'' ** Genus '' Gobicyon'' *** ''G. acutus'' *** ''G. macrognathus'' *** ''G. yei'' *** ''G. zhegalloi'' ** Genus '' Gustafsonia'' *** ''G. cognita'' (formerly ''Miacis cognitus'') ** Genus '' Guangxicyon'' *** ''G. sinoamericanus'' ** Genus '' Haplocyon'' *** ''H. elegans'' *** ''H. crucians'' ** Genus '' Haplocyonoides'' *** ''H. mordax'' *** ''H. serbiae'' *** ''H. ponticus'' ** Genus '' Haplocyonopsis'' ** Genus '' Harpagocyon'' ** Genus '' Harpagophagus'' ** ''Genus Ictiocyon''Ictiocyon'' at fossilworks
'' ** Genus ''

Myacyon ''Myacyon'' is an extinct genus of large sized carnivoran mammals, belonging to the family Amphicyonidae (“bear dogs”), that lived in Africa during the Miocene epoch. Due to the limited scope and fragmentary nature of the severely damaged holo ...

'' *** ''M. peignei'' ** Genus '' Paradaphoenus'' *** ''P. cuspigerus'' *** ''P. minimus'' *** ''P. tooheyi'' ** Genus '' Pseudarctos'' *** ''P. bavaricus'' ** Genus '' Pseudocyonopsis'' *** ''P. ambiguus'' *** ''P. antiquus'' *** ''P. quercensis'' ** Subfamily

Amphicyoninae Amphicyoninae is a subfamily of extinct bear-dogs, large terrestrial carnivores belonging to the suborder Caniformia and which inhabited North America, Eurasia, and Africa from ~37.2—2.6 Ma. Amphicyoninae existed for approximately ~. ...

*** Genus ''

'' **** ''A. frendens'' **** ''A. galushai'' **** ''A. giganteus'' **** ''A. ingens'' **** ''A. laugnacensis'' **** ''A. longiramus'' **** ''A. lyddekeri'' **** ''A. major ( type)'' **** ''A. palaeindicus'' *** Genus '' Cynelos'' **** ''C. caroniavorus'' **** ''C. crassidens'' **** ''C. helbingo'' **** ''C. idoneus'' **** ''C. jourdan'' **** ''C. lemanensis'' **** ''C. pivetaui'' **** ''C. rugosidens'' **** ''C. schlosseri'' **** ''C. sinapius'' *** Genus '' Goupilictis'' **** ''G. minor'' *** Genus ''

'' **** ''I. gidleyi'' ***Genus '' Magericyon'' **** ''M. anceps'' **** ''M. castellanus'' *** Genus ''

Pliocyon ''Pliocyon'' is an extinct genus of bear dogs which inhabited North America during the Middle Miocene 16.0—13.6 Ma, existing for approximately . Fossils have been uncovered in South Florida, Oregon, and western Nebraska Nebraska () is ...

'' **** ''P. medius'' **** ''P. robustus'' *** Genus '' Pseudamphicyon'' *** Genus '' Pseudocyon'' **** ''P. sansaniensis'' **** ''P. steinheimensis'' **** ''P. styriacus'' *** Genus '' Tartarocyon'' **** ''T. cazanavei'' ** Subfamily

Daphoeninae The Daphoeninae are an extinct subfamily of dog-like, terrestrial carnivores, which belonged to the family Amphicyonidae of the suborder Caniformia. The group inhabited North America from the Middle Eocene subepoch to the Middle Miocene subepo ...

(North America) *** Genus '' Adilophontes'' **** ''A. brachykolos'' *** Genus '' Brachyrhyncocyon'' **** ''B. dodgei'' **** ''B. montanus'' *** Genus '' Daphoenictis'' **** ''D. tedfordi'' *** Genus ''

'' **** ''D. falkenbachi'' **** ''D. notionastes'' **** ''D. robustum'' **** ''D. periculosus'' **** ''D. skinneri'' **** ''D. superbus'' *** Genus ''

'' **** ''D. felinus'' **** ''D. hartshornianus'' **** ''D. lambei'' **** ''D. nebrascensis'' **** ''D. socialis'' **** ''D. transversus'' **** ''D. vetus'' ** Subfamily Temnocyoninae (North America) *** Genus '' Mammacyon'' **** ''M. ferocior'' **** ''M. obtusidens'' *** Genus '' Temnocyon'' **** ''T. altigenis'' **** ''T. ferox'' **** ''T. percussor'' **** ''T. venator'' ** Subfamily ThaumastocyoninaeMorales, J., O. Fejfar, E. Heizmann, J. Wagner, A. Valenciano, and J. bella. 2019
A new Thaumastocyoninae (Amphicyonidae, Carnivora) from the early Miocene of Tuchořice, the Czech Republic.
Fossil Imprint 75(3–4): 397–411. *** Genus ''

'' **** ''A. antiquus'' *** Genus ''

Ammitocyon ''Ammitocyon'' is a genus of large sized carnivoran mammals, belonging to the Amphicyonidae ("bear dogs"), that lived during the Late Miocene in what is now Spain. It is notable for its extreme adaptations towards hypercarnivory, its extremely ...

'' **** ''A. kainos'' *** Genus '' Crassidia'' **** ''C. intermedia'' *** Genus '' Peignecyon'' **** ''P. felinoides'' *** Genus '' Thaumastocyon'' **** ''T. bourgeoisi'' **** ''T. dirus'' *** Genus '' Tomocyon'' **** ''T. grivense'' *** Genus '' Ysengrinia'' **** ''Y. americanus'' **** ''Y. depereti'' **** ''Y. geraniana'' **** ''Y. tolosana'' **** ''Y. valentiana''

References

External links

Whence the beardogs? Reappraisal of the Middle to Late Eocene ‘Miacis’ from Texas, USA, and the origin of Amphicyonidae
{{Taxonbar, from=Q248422 Prehistoric mammals of North America Eocene carnivorans Oligocene carnivorans Miocene carnivorans Pliocene extinctions Eocene first appearances Taxa named by Ernst Haeckel Prehistoric mammal families Fossil taxa described in 1886