Bear dog

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Temporal range: 42–2.6 Ma
Middle Eocene – Late Pliocene
Amphicyon ingens.JPG
Skeleton of Amphicyon
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Family: Amphicyonidae
Haeckel, 1886


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 Pliocene epoch 42–2.6 Mya, existing for about 39.4 million years.[1] Amphicyonids are often colloquially referred to as "bear-dogs". They are closely related to true dogs (Canidae) and a little less related to bears (Ursidae).


Restoration of Amphicyon ingens

The family was erected by Haeckel (1886) [also attributed to Trouessart (1885)]. While amphicyonids were previously thought to be closely related to ursids (bears),[2] there is increasing evidence that they may be basal caniforms.[3][4][5]


Amphicyonids ranged in size from as small as 5 kg (11 lb) and as large as 100 to 773 kg (220 to 1,704 lb)[6] and evolved from wolf-like to bear-like body forms.[7] 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;[8] the amphicyonids were obligate carnivores, unlike the Canidae, which are hypercarnivores or mesocarnivores.[9]

There is often some confusion with the similar looking (and similarly named) "dog-bears", which are members of the family Hemicyonidae.


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.[3]

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;[4][10] 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.[10]

New World daphoenines (Daphoenodon, Borocyon) and temnocyonines coexisted with Old World amphicyonines 23.7 to 17.5 million years ago. With estimated weights of 50 to 200 kg (110 to 440 lb), these were the largest terrestrial carnivorans to have evolved on the North American continent up to this time.[citation needed] 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 late Pliocene, classically named Arctamphicyon lydekkeri, which may actually be synonymous with a species of Amphicyon.[11]



  1. ^ Paleobiology Database: Amphicyonidae, age range and collections[failed verification]
  2. ^ R. M. Hunt. 2001. Small Oligocene amphicyonids from North America (Paradaphoenus, Mammalia, Carnivora). American Museum Novitates 3331:1-20
  3. ^ a b 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
  4. ^ a b Hunt, Robert M, Jr. (2004) "Global Climate and the Evolution of Large Mammalian Carnivores during the Later Cenozoic in North America" Archived July 20, 2007, at the Wayback Machine in Cenozoic Carnivores and Global Climate by Robert M. Hunt, Jr. Bulletin of the American Museum of Natural History (285) 139-285
  5. ^ M. Morlo, E. R. Miller, and A. N. El-Barkooky. 2007. Creodonta and Carnivora from Wadi Moghra, Egypt. Journal of Vertebrate Paleontology 27(1):145-159
  6. ^ Sorkin, B. 2008: A biomechanical constraint on body mass in terrestrial mammalian predators. Lethaia, Vol. 41, pp. 333–347.
  7. ^ Jacobs, Louis L. Jacobs; Scott, Kathleen Marie: Evolution of Tertiary Mammals of North America: Terrestrial carnivores, Cambridge University Press, 1998
  8. ^ Wang, Xiaoming and Tedford, Richard H. Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, 2008. p10-11, 29
  9. ^ Hunt, R. M. Jr. (1998). "Amphicyonidae". In Janis, Christine M.; Scott, Kathleen M.; Jacobs, Louis L. (eds.). Evolution of Tertiary Mammals of North America, volume 1: Terrestrial carnivores, ungulates, and ungulatelike mammals. Cambridge, England: Cambridge University Press. pp. 196–227. ISBN 978-0-521-35519-3.
  10. ^ a b Hunt, Robert M, Jr. 2003. Intercontinental Migration of Large Mammalian Carnivores: Earliest Occurrence of the Old World Beardog Amphicyon (Carnivora, Amphicyonidae) in North America. Bulletin of the American Museum of Natural History (279) 77-115
  11. ^ Stéphane Peigné (2006). "A new amphicyonid (Mammalia, Carnivora, Amphicyonidae) from the late middle Miocene of northern Thailand and a review of the amphicyonine record in Asia". Thailand Journal of Asian Earth Sciences. 26 (5): 519–532. doi:10.1016/j.jseaes.2004.11.003.

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