Temporal range: Aquitanian–Tortonian Early to Late Miocene
|A. ingens, American Museum of Natural History|
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 Aquitanian Epoch until the Tortonian. They ranged over North America, Europe, Asia, and Africa from 20.6—9 Ma ago, existing approximately .
Amphicyon was the typical bear-dog amphicyonid with morphology similar to both bears and dogs. With its robust build and maximum length of 2.5 m (8 ft), the largest species looked more like a bear than a dog. It had a large heavy tail, thick neck, robust limbs and teeth like a wolf. It was probably an omnivore with a lifestyle comparable to that of the brown bear.
A single specimen was examined by Legendre and Roth and estimated to have a body mass of 84.2 kg (190 lb), roughly half that of Ischyrocyon and twice that of Epicyon which shared its time period and habitat. A. ingens was much bigger: Sorkin (2008) estimated the largest known specimen (AM 68108) to weigh 600 kg, making it one of the largest known amphicyonids.
The earliest occurrences of Amphicyon in North America are from the early to mid-Miocene, found in the Runningwater Formation in Sioux County, Nebraska, and from the lower part of the Troublesome Formation, Colorado (A. galushai, A. frendens, and A. ingens). Although other large amphicyonids from the Miocene of North America have been placed in Amphicyon, many of these carnivores are now placed in other amphicyonid genera. The Amphicyon lineage in the New World is restricted to the above three species (18.8–14.2 Ma). Particularly rich samples of the large North American species of Amphicyon have been found in the Sheep Creek Formation (A. frendens) and Olcott Formation (A. ingens) of central Sioux County, northwest Nebraska. Amphicyon has also been found in France, Spain in Europe.
Amphicyon major. It lived from 16.9–9.0 Ma, approximately . Specimens have been found in across Europe and in western Turkey. The species was named by De Blainville in 1841. A. major was large in size, comparable to a modern lion or tiger.[better source needed] The estimated mass of Amphicyon major is around 180 kg (397 lb) with the functions derived for limb bones and craniodental measurements.
Amphicyon giganteus. It was a widespread European species that lived during the early burtigalian to early Langhian, approximately from 20.4–15.9 Mya, with possible material from Namibia. The species was first described in 1884 by Kaup. A specimen of Iberotherium rexmanueli zbyszewskii with teeth marks from A. giganteus was found in Portugal. It is unknown if the young Iberotherium was attacked or the carcass found and scavenged. The find was described by paleontologists Antunesa et al. in 2006.
Amphicyon galushai. The first occurrence of Amphicyon in North America, from approximately 18.8–17.5 Mya during the early Hemingfordian. Described by Robert M. Hunt Jr. in 2003, it is mostly known from fossils found in the Runningwater Formation of western Nebraska, a complete adult skull, a partial juvenile skull, 3 mandiblues and teeth and postcranial elemenents representing least 15 individuals. In addition there's a skull fragment from the Troublesome Formation of Colorado. It is considered ancestral to the late Hemingfordian species, A. frendens.
Amphicyon frendens. This specied lived during the late Hemingfordian, 17.5–15.9 Mya, The species was originally described by W. Matthew in 1924 from specimens found in the middle member of the Sheep Creek Formation, Sioux County, Nebraska. A. frendens specimens have since been found at sites in Harney and Malheur Counties, Oregon. A specimen examined by S. Legendre and C. Roth in 1988 yielded an estimated body mass of 135.6 kg (300 lb), similar to that of Ischyrocyon, Amphicyon galushai and its borophagine competitor Epicyon, which it coexisted with.
Amphicyon ingens. It lived during the early to middle Barstovian, 15.8–14.0 Mya. The species was originally described by W. Matthew in 1924 from specimens found in the Olcott Formation, Sioux County, Nebraska. Specimens attributed to this species have since been found in California, Colorado, and New Mexico.
- Hunt, Robert M. (2003). "Intercontinental Migration of Large Mammalian Carnivores: Earliest Occurrence of the Old World Beardog Amphicyon (Carnivora, Amphicyonidae) in North America.". Bulletin American Museum of Natural History 279: 77–115. doi:10.1206/0003-0090(2003)279<0077:c>2.0.co;2.
- PaleoBiology Database: Ischyrocyon
- S. Legendre and C. Roth. 1988. Correlation of carnassial tooth size and body weight in recent carnivores (Mammalia). Historical Biology 1(1):85-98
- Sorkin, B. (2008-04-10). "A biomechanical constraint on body mass in terrestrial mammalian predators". Lethaia 41 (4): 333–347. doi:10.1111/j.1502-3931.2007.00091.x. Retrieved 2011-08-02.
- Rafael Fraguas (January 7, 2010). "Animales prehistóricos en el Metro". El País (in Spanish) (Madrid).
- Paleobiology Database: Amphicyon major
- National Geographic Prehistoric Mammals by Alan Turner
- Figueirido et al. (2011). "Body mass estimation in amphicyonid carnivoran mammals: A multiple regression approach from the skull and skeleton.". Acta Palaeontologica Polonica 56 (2): 225–246. doi:10.4202/app.2010.0005.
- Hunt, Robert M. (1998). "Amphicyonidae". In Janis, C. M., Scott, K.M. & Jacobs, L. L. Evolution of tertiary mammals of North America, volume 1: Terrestrial carnivores, ungulates and ungulatelike mammals. Cambridge,UK: Cambridge University Press. pp. 196–227. ISBN 0521355192.
- Pickford et al. (1996). "Preliminary results of new excavations at Arrisdrift, middle Miocene of southern Namibia". C. R. Acad. Sci. Paris II (332): 991–996.
- Catalogue of the Fossil Mammalia in the British Museum Natural History, Dept. of Geology, Richard Lydekker
- M. T. Antunes et al. (2006). "Ichnological evidence of a Miocene rhinoceros bitten by a bear-dog (Amphicyon giganteus)". Annales de Paléontologie 92: 31–39. doi:10.1016/j.annpal.2005.10.002.
- W. D. Matthew. 1924. Third contribution to the Snake Creek Fauna. Bulletin of the American Museum of Natural History 50:59-210
- Sorkin, B. (2006). "Ecomorphology of the giant bear-dogs Amphicyon and Ischyrocyon". Historical Biology 18 (4): 375–388. doi:10.1080/08912960600618073.