Bear dog

This article is about the extinct family of mammals. For the breeds of domestic dog, see Karelian Bear Dog and Tahltan 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
Superfamily: Arctoidea?
Family: †Amphicyonidae
Haeckel, 1886
Subfamilies

†Amphicyoninae

†Daphoeninae
†Temnocyoninae

Amphicyonidae, colloquially known as "bear dogs", is an extinct family of large terrestrial carnivores belonging to the suborder Caniformia (meaning "dog-like"), which inhabited North America, Europe, Asia, and Africa from the Middle Eocene subepoch to the Pleistocene epoch 46.2—1.8 Mya, existing for approximately 44.4 million years.[1]

Taxonomy

An artist's reconstruction of a bear dog

Amphicyonidae was named 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

Amphicyonids, often referred to as "bear dogs", crossed from Europe to North America during the Miocene epoch and are considered an Old World taxon. The earliest to appear is the (rather large) Ysengrinia (30—20 Mya), followed by Cynelos (24—7 Mya) and Amphicyon (23—5 Mya). These animals would have followed ungulates and other mammals to the New World for a period of about 7 million years. The New World amphicyonids of the subfamilies Daphoeninae (42-16 Mya) and Temnocyoninae (33-20 Mya) coexisted with the Old World counterparts.[5] Note that the (often similar looking) members of the family Hemicyonidae are also often called "bear-dogs" (although they are increasingly referred to as "dog-bears" to avoid confusion).

Amphicyonids were as small as 5 kg (11 lb) and as large as 100 to 600 kg (220 to 1,320 lb)[6] and evolved from wolf-like to bear-like.[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]

Evolution

While amphicyonids have traditionally been viewed as closely related to ursids (bears), some evidence suggests they may instead be basal caniforms. (Hunt, 2004b). They were about as tall as the American black bear and were most likely ambushers because their legs were made for short, sudden bursts of speed. Bear dogs also nested their young in underground burrows.

During the early Miocene, a number of large amphicyonids 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.[5] 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 kilograms (110 to 440 lb) to have evolved on the North American continent up to this time. The immigrant 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.[10]

Amphicyonids began to decline in the late Miocene, and largely disappeared in the Pliocene; the reasons for this are unclear, with the most blamed factor being competition with other carnivorans, though there is no direct evidence for this. The youngest 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.[11]

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 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
  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. and 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.
  10. ↑ 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
  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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