Amphicyonidae is an extinct family of large terrestrial carnivorans belonging to the suborder Caniformia which inhabited North America, Europe, Asia, and Africa from the Middle Eocene subepoch to the Pleistocene epoch 46.2â€"1.8 Mya, existing for about 44.4 million years. Amphicyonids are often colloquially referred to as "bear-dogs", but are more closely related to true dogs (Canidae) than to bears (Ursidae).
Taxonomy
The family was erected by Haeckel (1886) [also attributed to Trouessart 1885]. While amphicyonids were previously thought to be closely related to ursids (bears), there is increasing evidence that they may be basal caniforms.
Description
Amphicyonids ranged in size from as small as 5Â kg (11Â lb) and as large as 100 to 600Â kg (220 to 1,320Â lb) and evolved from wolf-like to bear-like body forms. Early amphicyonids, such as Daphoenodon, possessed a digitigrade posture and locomotion (walking on their toes), while many of the later and larger species were plantigrade or semiplantigrade. The amphicyonids were obligate carnivores, unlike the Canidae, which are hypercarnivores or mesocarnivores.
There is often some confusion with the similar looking (and similarly named) "dog-bears", which are members of the family Hemicyonidae.
Evolution
It is uncertain where amphicyonids originated. It was thought that they may have crossed from Europe to North America during the Miocene epoch, but recent research suggests a possible North American origin from the miacids Miacis cognitus and M. australis (now renamed as the genera 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.
During the early Miocene, a number of large amphicyonids are thought to have migrated from Eurasia into North America. These taxa belong to the Old World amphicyonid subfamily Amphicyoninae. The earliest to appear is the large bear dog Ysengrinia Ginsburg, followed by Cynelos Jourdan, and then by Amphicyon. This influx of amphicyonines, accompanied by Old World ungulates and small mammals, indicates a prolonged interval (from 23 to 16.5 Mya) of faunal exchange between Asia and North America in the early Miocene, using the trans-Beringian route.
New World daphoenines (Daphoenodon, Borocyon) and temnocyonines coexisted with Old World amphicyonines 23.7-17.5 million years ago. With estimated weights of 50 to 200Â kg (110 to 440Â lb), these were the largest terrestrial carnivorans to have evolved on the North American continent up to this time. Other New World amphicyonids include the oldest known amphicyonid, Daphoenus (37-16 Mya).
Amphicyonids began to decline in the late Miocene, and largely disappeared in the Pliocene. The reasons for this are unclear: possibly it was due to competition with other carnivorans, but no direct evidence for this has been found. The most recent known amphicyonid remains are teeth known from the Dhok Pathan horizon, northern Pakistan, dating to the early Pleistocene, classically named Arctamphicyon lydekkeri, which may actually be synonymous with a species of Amphicyon.
Classification
- Family Amphicyonidae
- Genus Gustafsonia
- G. australis (formerly Miacis cognita)
- Genus Angelarctocyon
- A. australis (formerly Miacis australis)
- Subfamily Amphicyoninae
- Genus Agnotherium
- A. antiquus
- A. grivense
- Genus Amphicyon
- A. frendens
- A. galushai
- A. giganteus
- A. ingens
- A. laugnacensis
- A. longiramus
- A. lyddekeri
- A. major (type)
- A. palaeindicus
- Genus Amphicyonopsis
- A. serus
- Genus Brachycyon
- B. reyi
- B. palaeolycos
- B. gaudryi
- Genus Cynelos
- C. caroniavorus
- C. crassidens
- C. helbingo
- C. idoneus
- C. jourdan
- C. lemanensis
- C. pivetaui
- C. rugosidens
- C. schlosseri
- C. sinapius
- Genus Cynodictis
- C. lacustris
- Genus Euroamphicyon
- E. olisiponensis
- Genus Gobicyon
- G. macrognathus
- G. zhegalloi
- Genus Goupilictis
- G. minor
- Genus Guangxicyon
- G. sinoamericanus
- Genus Haplocyon
- H. elegans
- H. crucians
- Genus Haplocyonoides
- H. mordax
- H. serbiae
- H. ponticus
- Genus Haplocyonopsis
- Genus Harpagocyon
- Genus Heducides
- Genus Ischyrocyon
- I. gidleyi
- Genus Paradaphoenus
- P. cuspigerus
- P. minimus
- P. tooheyi
- Genus Pericyon
- Genus Pliocyon
- P. medius
- P. robustus
- Genus Proamphicyon
- Genus Protemnocyon
- Genus Pseudarctos
- P. bavaricus
- Genus Pseudamphicyon
- P. bavaricus
- Genus Pseudocyon
- P. sansaniensis
- P. steinheimensis
- P. styriacus
- Genus Pseudocyonopsis
- P. ambiguus
- P. antiquus
- P. quercensis
- Genus Symplectocyon
- Genus Ysengrinia
- Y. americanus
- Y. depereti
- Y. geraniana
- Y. ginsburg
- Y. tolosana
- Tribe Thaumastocyonini
- Genus Agnotherium
- Subfamily Daphoeninae (North America)
- Genus Adilophontes
- A. brachykolos
- Genus Borocyon
- Genus Brachyrhyncocyon
- B. dodgei
- B. montanus
- Genus Daphoenictis
- D. tedfordi
- Genus Daphoenodon
- D. falkenbachi
- D. notionastes
- D. robustum
- D. periculosus
- D. skinneri
- D. superbus
- Genus Daphoenus
- D. felinus
- D. hartshornianus
- D. lambei
- D. nebrascensis
- D. socialis
- D. transversus
- D. vetus
- Genus Paradaphoenus
- P. cuspigerus
- P. minimus
- P. tooheyi
- Genus Adilophontes
- Subfamily Temnocyoninae (North America)
- Genus Mammacyon
- M. obtusidens
- Genus Temnocyon
- T. altigenis
- T. ferox
- T. percussor
- T. venator
- Genus Mammacyon
- Genus Gustafsonia
References
External links
- Whence the beardogs? Reappraisal of the Middle to Late Eocene ‘Miacis’ from Texas, USA, and the origin of Amphicyonidae
