Amphicyonidae Basics

[brobear]

Amphicyonidae


Amphicyonidae
Temporal range: 46.2–1.8 Ma
PreЄЄOSDCPTJKPgN
Middle Eocene - Early Pleistocene
Amphicyon ingens.JPG
Skeleton of Amphicyon
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Caniformia
Family: †Amphicyonidae
Haeckel, 1886
Subfamilies
†Amphicyoninae

†Thaumastocyonini
†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. Amphicyonids are often colloquially referred to as "bear-dogs", but are more closely related to true dogs (Canidae) than to bears (Ursidae).

The family was erected by Haeckel (1886) [also attributed to Trouessart 1885]. While amphicyonids were previously thought to be closely related to ursids (bears), there is increasing evidence that they may be basal caniforms.

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) and evolved from wolf-like to bear-like body forms. 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. The amphicyonids were obligate carnivores, unlike the Canidae, which are hypercarnivores or mesocarnivores.

There is often some confusion with the similar looking (and similarly named) "dog-bears", which are members of the family Hemicyonidae.

It is 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 miacids Miacis cognitus and M. australis (now renamed as the genera Gustafsonia 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.

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.

New World daphoenines (Daphoenodon, Borocyon) and temnocyonines coexisted with Old World amphicyonines 23.7-17.5 million years ago. With estimated weights of 50 to 200 kg (110 to 440 lb), these were the largest terrestrial carnivorans to have evolved on the North American continent up to this time.[citation needed] Other New World amphicyonids include the oldest known amphicyonid, Daphoenus (37-16 Mya).

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.

[brobear]

www.livescience.com/56795-bear-dog.html

Facts About the Bear Dog
By Alina Bradford, Live Science Contributor | November 8, 2016

The bear dog, also called Amphicyon, shared features of bears (heavy-bodied, with feet planted flat on the ground) and dogs (relatively long legs and long snout), but they are neither bears (family Ursidae) nor dogs (family Canidae).

They were not specifically in the bear's or dog's scientific families, but they are classified in the Caniformia, or "dog-like" suborder. Modern animals in the Caniformia suborder include wolves, foxes, dogs, bears, sea lions and weasels. This makes bear dogs something like cousins to their namesakes. Also, these bear dogs should not be confused with the modern dog breed, the Karelian bear dog.

There were two main types of bear dogs. Some, like Borocyon robustum, had long limbs that were ideal for running and looked much like modern wolves. Others, such as Amphicyon longiramus, were stocky and looked more like modern bears, according to the Florida Museum of Natural History.

Much like dogs and bears of today, bear dogs had a range of sizes. They could weigh just few pounds or grow to over 1,000 lbs. (450 kilograms). It is thought that the early evolutions of the bear dog were very small, around Chihuahua size. As they continued to evolve, they seemed to have become progressively larger, according to The Field Museum.

Evolving into bigger animals has several advantages and disadvantages. While becoming bigger would have enabled them to take down bigger prey and be higher on the food chain, they also would have required more food and reproduced more slowly.

"Their massiveness suggest that they could prey upon many kinds of mammals and other animals. Fortunately, they were extinct before humans appeared on the scene," said Wilkins.

Bear dogs first appeared in Eurasia during the Eocene and Oligocene epochs (55.8 million to 23 million years ago), time periods full of warm weather and thick vegetation. The temperature around the world stayed around 86 degrees Fahrenheit (30 Celsius) during the Eocene period, according to the University of California Museum of Paleontology.

Though the temperatures cooled in the Oligocene, it was still quite warm and vegetation flourished in most locations around the world, including North America and Africa. Bear dogs became extinct 5 million to 10 million years ago.

The bear dog's teeth were shaped to allow for an omnivorous diet, much like modern bears and modern dogs. Prey for smaller bear dogs may have included rodents while bigger beardogs would have eaten larger animals such as wild hogs. Bear dogs may have also enjoyed leaves and berries.

[Just the facts, man,]

Apr 12, 2018 1:13:46 GMT -5 brobear said:

www.livescience.com/56795-bear-dog.html

Much like dogs and bears of today, bear dogs had a range of sizes. They could weigh just few pounds or grow to over 1,000 lbs. (450 kilograms). It is thought that the early evolutions of the bear dog were very small, around Chihuahua size. As they continued to evolve, they seemed to have become progressively larger, according to The Field Museum.

Evolving into bigger animals has several advantages and disadvantages. While becoming bigger would have enabled them to take down bigger prey and be higher on the food chain, they also would have required more food and reproduced more slowly.

"Their massiveness suggest that they could prey upon many kinds of mammals and other animals. Fortunately, they were extinct before humans appeared on the scene," said Wilkins. 

 Bear dogs became extinct 5 million to 10 million years ago.

The bear dog's teeth were shaped to allow for an omnivorous diet, much like modern bears and modern dogs. Prey for smaller bear dogs may have included rodents while bigger beardogs would have eaten larger animals such as wild hogs. Bear dogs may have also enjoyed leaves and berries.


A few points about this post.
Modern bears and (wild) dogs do not have a like "range of sizes", and in fact, wild dog upper size range (for adults) pretty much stops, before bears even begin.

Of current mammalian carnivores, only felids naturally occur in such a wide size range (20 fold), and yet musculo-skeletal morphology studies show
that all modern cats share pretty much the same bauplan, (along with a  very large % of the same genome), with the very obvious cheetah, as an outlier.

Other paleolozoological studies show that a number of larger true dog species beacme extinct coincident with the arrival of felids.

Similarly, the borophagous 'bear dogs' were likely out-competed by the felid branch which became the modern hyenas.

[brobear]

www.prehistoric-wildlife.com/species/a/amphicyon.html

Amphicyon.

Name: Amphicyon (Ambiguous dog).
Phonetic: Am-fee-cie-on.
Classification: Chordata, Mammalia, Carnivora, Amphicyonidae, Amphicyoninae.
Species: A. intermedius (type), A. frendens, A. frendes, A. galushai, A. giganteus, A. ingens, A. laugnacensis, A. longiramus, A. major, A. pontoni, A. reinheimeri, A. riggsi.
Diet: Primarily carnivorous but also thought to be an omnivore.
Size: Up to 2.5 meters long, but exact size depends upon species.
Known locations: Europe, Middle East, Asia, North America and Southern Africa.
Time period: Aquitanian through to Tortonian of the Miocene.
Fossil representation: Many known specimens allowing for complete restorations.

In popular culture Amphicyon is possibly the best known genera of the group known as ‘bear dogs’. This group was so named because of the immensely robust build of the body that gave them the appearance of bears even though the heads were more dog-like. Despite this more general name, Amphicyon was not a true dog, although it did live alongside animals that were more closely related to true dogs such as Epicyon.
Amphicyon was one of the larger examples of the bear dogs, and of the known species A. ingens from North America is often cited as one of the largest. It’s thought that the arrival of amphicyonine bear dogs in North America replaced older carnivores like Hyaenodon as the dominant predators of the land until they themselves were replaced by a combined emergence of new feline and canid predators.
Although Amphicyon is thought by many to have been an omnivore, it still had dedicated adaptations for hunting. Its sheer physical size meant that it was capable of overpowering many of the potential prey items that it came into contact with, and the especially well developed forelimbs suggest it was capable of wrestling prey to the ground. However this strength came at the price of speed, so Amphicyon would have been restricted to prey that could not run away from it, possibly larger and slower but more powerful animals like Chalicotherium that would have necessitated the extra strength.
The concept of pack behaviour in Amphicyon has been considered by some, but while it is a possibility there is so far very little in the way of direct evidence to support this behaviour. If Amphicyon was a solitary hunter it may have eventually had to go up against pack animals like wolves, and while some solitary predators can and do hold their ground against wolf packs (as can be witnessed today with grizzly bears stealing the kills from packs of grey wolves), this is not an absolute rule that can be applied to everything. Such competition could be a key part of the ultimate downfall of Amphicyon as a dominant carnivore, as well as a seeming shift of herbivorous prey animals becoming larger, faster and more powerful in their own rights, meaning that Amphicyon no longer had a size advantage, but possibly a size hindrance.
     

[brobear]

Bear-Dogs 
                       

[brobear]

Beardogs weren't bears nor dogs, but relatives of both that were found across most of the world for nearly 40 million years.

While some were lithe and agile like dogs, others amped up their bearness by being massive and stocky.

These are Amphicyon, Borocyon and Ischyrocyon

by Julio Lacerda

[brobear]

There is often some confusion between Hemicyonidae and Amphicyonidae.

1- Hemicyonidae is the "Dog Bear".
2- Amphicyonidae is the "Bear Dog".

animals.fandom.com/wiki/Amphicyonidae

The Amphicyonidae is an extinct family of large terrestrial carnivores, 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.

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. Note that the (often similar looking) members of the family Hemicyonidae are also often called "bear-dogs".

Amphicyonidae
Amphicyon ingens
Amphicyon ingens skeleton
Scientific Classification
Kingdom Animalia
Phylum Chordata
Class Mammalia
Order Carnivora
Family †Amphicyonidae
The Amphicyonidae is an extinct family of large terrestrial carnivores, 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.

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. Note that the (often similar looking) members of the family Hemicyonidae are also often called "bear-dogs".

Amphicyonids were as small as 5 kg (11 lb) and as large as 100 to 600 kg (220 to 1,300 lb) and evolved from wolf-like to bear-like. 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. The amphicyonids were obligate carnivores, unlike the Canidae, which are hypercarnivores or mesocarnivores.

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.

[brobear]

www.fieldmuseum.org/blog/fossil-beardogs-shed-light-evolution-dogs

Fossil "Beardogs" Shed Light On Evolution Of Dogs.

Members of the dog branch today include dogs, wolves, foxes, bears, sea lions, and weasels. Beardogs are from an earlier point in that group’s history, before they branched out into the dog relatives we see today. “They’re equally related to all of the dog relatives alive today—they’re not the direct ancestors of modern wolves and bears, but more like their cousins,” explains Tomiya.

[brobear]

Body Mass Estimation in Amphicyonid Carnivoran Mammals: A Multiple Regression Approach from the Skull and Skeleton

Abstract
The body masses of sixteen species of amphicyonids (Mammalia, Carnivora, Amphicyonidae) from the New and Old World were estimated on the basis of 86 osteological variables measured from the craniodental (N = 44) and postcranial (N = 42) skeleton of living species of Canidae and Ursidae. Given the absence of complete and well preserved skeletons of amphicyonids in the fossil record, multiple regression functions were derived separately from measurements taken from the mandible, the cranium and the major limb bones. The accuracy of the regression functions was evaluated using the percentage prediction error and the percentage standard error of the estimates. Mass values were calculated with these equations using measurements taken in adult individuals from a number of daphoenine and amphicyonine species. Results obtained show that three distinct size classes of amphicyonids emerged through the evolutionary history of the “beardog” family and that these size classes correlate with presumably different ecomorphs. Quantitative estimates of body size of amphicyonids are critical for deciphering the paleobiology of this poorly understood family of large fissiped carnivorans and can be used for placing it within a broader ecological context.

[brobear]

Morphofunctional analysis of the postcranium of Amphicyon major (Mammalia, Carnivora, Amphicyonidae) from the Miocene of Sansan (Gers, France) compared to three extant carnivores: Ursus arctos, Panthera leo, and Canis lupus

sciencepress.mnhn.fr/en/periodiques/geodiversitas/32/1/analyse-morphofonctionnelle-du-squelette-postcranien-d-amphicyon-major-mammalia-carnivora-amphicyonidae-du-miocene-de-sansan-gers-france-compare-trois-carnivores-actuels-ursus-arctos-panthera-leo-et-canis-lupus

Published on 30 March 2010

The postcranial skeleton of the amphicyonid Amphicyon major from the middle Helvetian of Sansan (Gers, France) is described and compared to extant taxa belonging to the families Ursidae (Ursus arctos), Felidae (Panthera leo), and Canidae (Canis lupus). From the perspective of the forelimb, the scapula is very similar to that of a bear, as well as the elbow joint suggesting habitually abducted postures of the arm and the ability to supinate the forefoot. The mobile shoulder joint and massive triceps are features shared by both extant ursids and felids. A powerful hand musculature, short and divergent metacarpals, and an important range of dorsifl exion of the wrist recall the forefoot of an ursid and indicate good grasping ability. On the axial skeleton, the complex atlas/axis, the shape of the lumbar vertebrae, and a long, heavy tail are more similar to the same anatomical regions in felids than to any other extant carnivore. The pelvis and femur, as well as the knee and tibio-astragalar joints, are also more similar to those of a felid than an ursid, although the ischium and femur of Amphicyon allowed more abducted and erected postures. The size and shape of the tibia, calcaneum, and metatarsals are more similar to those of a bear. The short metatarsals, with a divergent Mt I and a powerful hind foot musculature also suggest potential grasping ability. Therefore, the skeleton of Amphicyon major that displays a series of bear-like and cat-like morphological similarities would deserve the term of "bear-lion" instead of "bear-dog".