Amphicyonidae is an
extinctfamily of
terrestrialcarnivorans belonging to the
suborderCaniformia. They first appeared in
North America in the middle
Eocene (around 45 mya), spread to
Europe by the late Eocene (35 mya), and further spread to
Asia and
Africa by the early
Miocene (23 mya). They had largely disappeared worldwide by the late Miocene (5 mya), with the latest recorded
species at the end of the Miocene in Africa. They were among the first carnivorans to evolve large body size. Amphicyonids are colloquially referred to as "bear-dogs".[1]
Taxonomy
The family was erected by Haeckel in 1866 (also attributed to Trouessart 1885). Their exact position has long been disputed. Some early paleontologists defined them as members of the family
Canidae, but the modern consensus is that they form their own family. Some researchers have defined it as the sister clade to ursids (
bears), based on morphological analysis of the ear region.[2][1] However, cladistic analysis and reclassification of several species of early carnivore as amphicyonids has strongly suggested that they may be basal caniforms, from lineages older than the origin of both bears and dogs.[3][4][5]
Description
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]
There is often some confusion with the similar looking (and similarly named) "dog-bears", a more derived group of caniforms that is sometimes classified as a family (
Hemicyonidae), but is more often considered a primitive subfamily of ursids (
Hemicyoninae).
Evolution
It has long been 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
miacidsMiacis cognitus and M. australis (now renamed as the
generaGustafsonia 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]
Other New World amphicyonids include the oldest known amphicyonid, Daphoenus (37–16 Mya).
Amphicyonids began to decline in the late Miocene, and disappeared by the end of the epoch. The exact reasons for this are unclear. The most recent known amphicyonid remains are teeth known from the
Dhok Pathan horizon, northern
Pakistan, dating to 7.4-5.3 mya.[10] The species is classically named Arctamphicyon lydekkeri, which may actually be synonymous with a species of Amphicyon.[11]
Fossils of juvenile Agnotherium, Ischyrocyon, and Magericyon all show an unusual type of tooth eruption in which there is a vulnerable stage at about two or three years of age where the subadult animal has no functional
molar or
carnassial teeth, the only functional cheek teeth being several milk premolars.[12] This period was suggested to be "presumably short" but would have made it very difficult for the animal to process food.[13] This type of tooth replacement is not seen in similar carnivorans like
ursids or
canids, and may have been one factor in the extinction of the Amphicyonidae.
^
abWang, Xiaoming and Richard H. Tedford (2008). Dogs; their Fossil Relatives and Evolutionary History. Columbia University Press. pp. 10–11.
ISBN9780231135283.
^Sorkin, B. 2008: A biomechanical constraint on body mass in terrestrial mammalian predators. Lethaia, Vol. 41, pp. 333–347.
^Jacobs, Louis L. Jacobs; Scott, Kathleen Marie: Evolution of Tertiary Mammals of North America: Terrestrial carnivores, Cambridge University Press, 1998
^Wang, Xiaoming and Tedford, Richard H. Dogs: Their Fossil Relatives and Evolutionary History. New York: Columbia University Press, 2008. p10-11, 29
^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.
ISBN978-0-521-35519-3.
^Sehgal, R. K. and A. C. Nanda (2002). "Age of the fossiliferous Siwalik sediments exposed in the vicinity of Nurpur, District Kangra, Himachal Pradesh". Current Science. 82 (4): 392–395.
JSTOR24106648.
^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.
Bibcode:
2006JAESc..26..519P.
doi:
10.1016/j.jseaes.2004.11.003.
^Morlo, Michael; Bastl, Katharina; Habersetzer, Jörg; Engel, Thomas; Lischewsky, Bastian; Lutz, Herbert; von Berg, Axel; Rabenstein, Renate; Nagel, Doris (3 September 2019). "The apex of amphicyonid hypercarnivory: solving the riddle of Agnotherium antiquum Kaup, 1833 (Mammalia, Carnivora)". Journal of Vertebrate Paleontology. 39 (5): e1705848.
Bibcode:
2019JVPal..39E5848M.
doi:
10.1080/02724634.2019.1705848.
S2CID214431583.
^Morlo, Michael; Bastl, Katharina; Habersetzer, Jörg; Engel, Thomas; Lischewsky, Bastian; Lutz, Herbert; von Berg, Axel; Rabenstein, Renate; Nagel, Doris (3 September 2019). "The apex of amphicyonid hypercarnivory: solving the riddle of Agnotherium antiquum Kaup, 1833 (Mammalia, Carnivora)". Journal of Vertebrate Paleontology. 39 (5): e1705848.
Bibcode:
2019JVPal..39E5848M.
doi:
10.1080/02724634.2019.1705848.
S2CID214431583.
^
abJiangzuo, Q.; Wang, S.; et al. (September 2019). "New material of Gobicyon (Carnivora, Amphicyonidae, Haplocyoninae) from northern China and a review of Aktaucyonini evolution". Papers in Palaeontology. 7 (1): 307–327.
doi:
10.1002/spp2.1283.
S2CID204264754.
^Berger, Jean-Pierre (June 1998). "'Rochette' (Upper Oligocene, Swiss Molasse): a strange example of a fossil assemblage". Review of Palaeobotany and Palynology. 101 (1–4): 95–110.
Bibcode:
1998RPaPa.101...95B.
doi:
10.1016/S0034-6667(97)00071-7.
^Ginsburg, Léonard (2002). "Un Amphicyonidae (Carnivora, Mammalia) nouveau du Miocène moyen de Vieux-Collonges (Rhône)". Symbioses (in French). 7: 55–57.
^Wang, Xiaoming; Hong-jiang, Wang; Jiangzuo, Qigao (2016). "New record of a haplocyonine amphicyonid in early Miocene of Nei Mongol fills a long-suspected geographic hiatus". Vertebrata PalAsiatica. 54 (1): 21–35.