Bear dog

Amphicyonidae
Temporal range: 46.2–1.8 Ma

Middle Eocene - Early Pleistocene

Skeleton of Amphicyon
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Family: †Amphicyonidae
Haeckel, 1886
Subfamilies

†Amphicyoninae

†Daphoeninae
†Temnocyoninae

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 46.2—1.8 Mya, existing for about 44.4 million years.[1] Amphicyonids are often colloquially referred to as "bear-dogs", but are more closely related to true dogs (Canidae) than to bears (Ursidae).

Taxonomy

An artist's reconstruction of a bear dog

The family was erected by Haeckel (1886) [also attributed to Trouessart 1885]. It was assigned to Carnivora by Sach and Heizmann (2001); to Arctoidea by Hunt (2001), Hunt (2002), and Hunt (2002); affirmed as Arctoidea by Zhai et al. (2003); affirmed to Arctoidea by Carroll (1988), Hunt (1998), and Wang et al. (2005); and to Caniformia by Morlo et al. (2007).[2][3][4]

Origins

It is uncertain where Amphicyonids, often referred to as "bear dogs", 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 renamed Miacidae, Miacis cognitus and Miacis australis (now renamed as the genera Gustafsonia and Angelarctocyon respectively).[5] As these are of North American origin, but appear to be early amphicyonids, it may be that amphicyonidae actually originates in North America.

The New World amphicyonids include the oldest known amphicyonid, Daphoenus (37-16 Mya) and the subfamily Temnocyoninae (33-20 Mya). These coexisted with their Old World counterparts, including Ysengrinia (30—20 Mya), Cynelos (24—7 Mya) and Amphicyon (23—5 Mya).[6] There is often some confusion with the similar looking (and similarly named) "dog-bears", which are members of the family Hemicyonidae.

Amphicyonids ranged in size from as small as 5 kg (11 lb) and as large as 100 to 600 kg (220 to 1,320 lb)[7] and evolved from wolf-like to bear-like body forms.[8] 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.[9] The amphicyonids were obligate carnivores, unlike the Canidae, which are hypercarnivores or mesocarnivores.[10]

Evolution

While amphicyonids were previously thought to be closely related to ursids (bears), there is increasing evidence that they may be basal caniforms.[5][11]

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.[6] New World daphoenines (Daphoenodon, Borocyon) and temnocyonines coexisted with Old World amphicyonines (Ysengrinia, Amphicyon, Cynelos) 23.7-17.5 million years ago. These are the largest terrestrial carnivorans 50 to 200 kg (110 to 440 lb) to have evolved on the North American continent up to this time. The amphicyonines Ysengrinia, Cynelos and Amphicyon appear at 23, 19.2, and 18.8 Mya, respectively, and herald the beginning of a Eurasian amphicyonine migration into North America that continued into the mid-Miocene.[11]

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.[12]

Classification

See also

References

  1. ↑ Paleobiology Database: Amphicyonidae, age range and collections
  2. ↑ V. J. Sach and E. P. J. Heizmann. 2001. Stratigraphy and mammal faunas of the Brackwassermolasse in the surroundings of Ulm (Southwest Germany). Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 310:1-95
  3. ↑ R. M. Hunt. 2001. Small Oligocene amphicyonids from North America (Paradaphoenus, Mammalia, Carnivora). American Museum Novitates 3331:1-20
  4. ↑ 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
  5. 1 2 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
  6. 1 2 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
  7. ↑ Sorkin, B. 2008: A biomechanical constraint on body mass in terrestrial mammalian predators. Lethaia, Vol. 41, pp. 333–347.
  8. ↑ Jacobs, Louis L. Jacobs; Scott, Kathleen Marie: Evolution of Tertiary Mammals of North America: Terrestrial carnivores, Cambridge University Press, 1998
  9. ↑ Wang, Xiaoming and Tedford, Richard H. Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, 2008. p10-11, 29
  10. ↑ Hunt, R. M. Jr. (1998). "Amphicyonidae". In Janis, Christine M.; Scott, Kathleen M.; Jacobs, Louis L. 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.
  11. 1 2 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
  12. ↑ 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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