PrimalMustelid/sandbox Temporal range: Early Miocene to Late Miocene 10–7 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
A. ingens, American Museum of Natural History
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	†Amphicyonidae
Subfamily:	†Amphicyoninae
Genus:	†Amphicyon Lartet, 1836
Type species
†Amphicyon major[1] Blainville, 1841
Other species
A. frendens Matthew, 1924 A. galushai Hunt, 2003 A. giganteus Schinz, 1825 A. ingens Matthew, 1924 A. palaeindicus Lydekker, 1876 A. astrei Kuss, 1962 A. eppelsheimensis Weitzel, 1930 A. laugnacensis Ginsburg, 1989 A. gutmanni Kittl, 1891 A. zhanxiangi Jiangzuo et al, 2019 A. shahbazi Pilgrim, 1912 A. pithecophilus Pilgrim, 1932 A. lathanicus Ginsburg, 2000 A. olisiponensis Antunes & Ginsburg, 1977 A. ulungurensis Qi, 1989 A. tairumensis Colbert, 1939 A. confucianus? Young, 1937 A. pannonicus Kretzoi, 1985 A. cooperi Pilgrim, 1932 A. sindiensis Pilgrim, 1932 A. intermedius? White, 1940 A. lactorensis Astre, 1928 A. longiramus? Long, 1942 A. pontoni? Simpson, 1930 A. riggsi? McGrew, 1939 A. reinheimeri? Cook, 1926

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 Miocene epoch. Members of this family received their vernacular name for possessing bear-like and dog-like features. They ranged over North America, Europe, Asia, and Africa.

(Note: Family: Amphicyonidae/Subfamily: Amphicyoninae = Haeckel, 1866)

Morphology

Amphicyon was the typical 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. The Amphicyon was very large for predators of its time but this advantage eventually became a disadvantage because its large body mass was too large to take faster prey.^{[citation needed]}

A. major has been estimated to have had a body mass of 630 kg (1,400 lb),^[2] while A. ingens has been estimated around 600 kilograms (1,300 lb)^[3] making it one of the largest known amphicyonids.^{[citation needed]}

Behaviour

Amphicyon was long believed to have been an omnivore, but to have tended to eat more meat than plants or other foods. However, in a new study published in 2020, examination of the relative grinding area of the molars of Amphicyon indicates that it was predominantly or purely carnivorous, similar to most living canids.^[4] Both Amphicyon and its relative, Ischyrocyon, possessed skeletal features that are characteristic of both living ambush and pursuit predators. As such, it is believed that Amphicyon probably pursued prey for longer distances but at slower speeds than living ambush predators do. Upon catching up to its prey, Amphicyon probably grabbed its victims with its powerfully muscled forelimbs before killing them by tearing into the prey's ribcage or neck using its large, strong canines set in its narrow snout.^[4]

It is generally believed that Amphicyon lived on its own, unlike wolves.^[4] It is thought to have targeted slow or injured large prey like the Chalicotherium to feed its large appetite.^{[citation needed]}

Fossil distribution

Amphicyon has also been found in France and Spain^[5] in Europe. Amphicyon's youngest range is on the Indian subcontinent.^{[citation needed]}

Species

European Species

Amphicyon major lived from 16.9–9.0 Ma, for approximately 7.9 million years.^[6] Specimens have been found in across Europe and in western Turkey.^[6] The species was named by De Blainville in 1841.^[6] A. major was large in size, comparable to a modern lion or tiger.^{[7][better source needed]} The estimated mass of A. major is around 180 kg (397 lb) with the functions derived for limb bones and craniodental measurements.^[8]

Amphicyon giganteus was a widespread European species that lived during the late Burdigalian to late Seravallian, corresponding to the MN4-MN7/8.^[9][10] Fossils from this species are also known from the locality Arrisdrift in Namibia,^[11][12] and potentially from Gebel Zelten in Libya and Moghra in Egypt,^[13] although the referral of these fossils remains controversial.^[14] The species was first described in 1884 by Kaup.^[15] 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.^[16]

North American Species

Amphicyon galushai represents the first occurrence of Amphicyon in North America, 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 and includes a complete adult skull, a partial juvenile skull, 3 mandibles and teeth and postcranial elemenents representing least 15 individuals. There is an additional skull fragment from the Troublesome Formation of Colorado.^[1] A. galushai is considered ancestral to the late Hemingfordian species, Amphicyon frendens.^{[citation needed]}

A. frendens lived during the late Hemingfordian, 17.5–15.9 Mya.^[17] 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.^[18] 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),^[2] similar to that of Ischyrocyon, A. galushai, and its co-existing, borophagine competitor, Epicyon.^{[citation needed]}

Amphicyon ingens lived during the early to middle Barstovian, 15.8–14.0 Mya.^[19] The species was originally described by W. Matthew in 1924 from specimens found in the Olcott Formation, Sioux County, Nebraska.^[18] Specimens attributed to this species have since been found in California, Colorado and New Mexico.^{[citation needed]}

Asian Species

Amphicyon confucianus is known from a single, fragmentary right hemimandible, which includes p3 and m1. It is part of the Shanwang Local Fauna, which dates to ca. 16 Ma. It is a large species, comparable to A. ulungurensis in size. The attribution of this species to Amphicyon remains unclear,^[20][21] although it probably does not belong to this genus.^[22]

Amphicyon ulungurensis is known from the middle Miocene Halamagai Formation. Due to the lack of observation on the characteristics of the upper molars, there is neither evidence for including it nor for excluding it from the genus.^[22]

Amphicyon zhanxiangi was described in 2018 based on a maxillary fragment from the Zhang’enbao Formation in Ningxia, China. The Yinziling subfauna to which it belongs dates to the late Shanwangian, roughly corresponding to MN5.^[22] It has also been reported from the slightly younger locality Lagou, part of the Hujialiang Formation, in the Linxia Basin, dating to the Tunggurian, which is equivalent to MN6.^[23] Unlike other Asian species, its referral to Amphicyon is definite. It is medium-sized, comparable to A. major, and closely related to A. giganteus.^[22] Over time, the diet of the species adapted towards omnivory as it moved towards more southern and humid areas, where greater amounts of plant material were available. The Lagou specimen showing greater adaptions to omnivory than the older one from Ningxia, which lived farther to the north, in a more arid terrain. This trend likely continued, with A. zhanxiangi being the probable ancestor of Arctamphicyon.^[23]

Amphicyon lydekkeri is known from the Dhok Pathan horizon in Pakistan and was described by Pilgrim in 1910, who later attributed it to its own genus, Arctamphicyon. However, Pilgrim identified the holotype as first m1 and then as M1, despite it actually being a M2, making the diagnosis invalid. It has furthermore been argued that the differences between “Arctamphicyon” and Amphicyon are negligible, with the former being a junior synonym of the latter.^[24] Other authors consider the differences distinct enough for the separation of the two genera.^[22] Fossils from Yuanmou in Yunnan, and the Lower Irrawaddy Formation in Myanmar, show affinities to this species, and have been assigned to Arctamphicyon.^[23] Amphicyon palaeindicus was described by Richard Lydekker in 1876 on the basis of an isolated M2 collected at Kushalgarh in the Potwar Plateau.^[25] Later authors referred a fragmentary mandible from Chinji,^[26] isolated teeth from the Chinji and the Nagri zones,^[27] and the Dang Valley,^[28] to this species. The exact age of the Chinji specimens cannot be defined, as the fossil-bearing localities in this region stretch from ca. 15 to 9 Ma, although the correlation of the Dang Valley fauna suggests that they're of late middle Miocene age,^[20] whereas the Nagri fauna dates to the Vallesian.^[29] It has been suggested that none of the Siwalik species truly belong to Amphicyon,^[30] although others suggests that A. palaeindicus should be referred to this genus.^[21]

Amphicyon pithecophilus was erected by Pilgrim in 1932 on basis of an isolated m2 from Chinji. He furthermore assigned two fragmentary mandibles, from Chinji and Nurpur, previously referred to A. palaeindicus to this species.^[31] Colbert considered it a synonym of that species,^[32] although later authors considered it distinct due to its larger metacone and stronger buccal cingulum on the M2.^[20][22]

References

Category:Bear dogs Category:Oligocene caniforms Category:Miocene bear dogs Category:Miocene mammals of Asia Category:Miocene mammals of North America Category:Aquitanian genus first appearances Category:Tortonian extinctions Category:Fossil taxa described in 1836 Category:Prehistoric carnivoran genera