Epicyon Saevus FLMNH

''Epicyon'' ("more than a dog") is a large, extinct, canid genus of the subfamily Borophaginae ("bone-crushing dogs"), native to North America. ''Epicyon'' existed for about from the early Clarendonian age of the Late Miocene to the late Hemphillian age of the Early Pliocene.'''' ''E. haydeni'' is the largest known canid of all time, with the type species reaching 2.4 m (7.9 ft) in length, 90 cm (35 in) in shoulder height and approximately 100–125 kg (220–276 lb) in body mass.Díaz-Sibaja, R. (2010). "Titanes Vol. 1 Mamíferos." ''Fósil Revista de Paleontología''. The largest known humerus specimen belonged to an individual weighing up to .

Taxonomy

''Epicyon'' was first named by Joseph Leidy in 1858 as a subgenus of ''Canis''. It was also mentioned as belonging to the Aelurodontina by Matthew and Stirton in 1930. Later studies indicates that it was not a species of ''Canis'', but a borophagine.

''Epicyon haydeni'', the type species, existed from 10-5 million years ago. It is synonymous with ''Aelurodon aphobus, Osteoborus ricardoensis, Osteoborus validus, ''and ''Tephrocyon mortifer,'' and was named by Joseph Leidy as a subgenus. It was recombined as ''Aelurodon haydeni'' by Scott and Osborn in 1890. Further study by Matthew in 1899, Matthew and Gidley in 1904, VanderHoof and Gregory in 1940, McGrew in 1944, Bennett in 1979, (1979) and Becker (1980). It again was recombined as ''Epicyon haydeni'' by Baskin in 1980, Voorhies in 1990, (1990), Baskin (1998), Wang et al. in 1999.

''Epicyon saevus'' existed from 12 to 7 million years ago. It is synonymous with ''Aelurodon inflatus'' and was named by Joseph Leidy in 1858 or 1859. In the late 1880s-early 1900s, Scott, Matthew, Cope and Matthew, Troxell recombined the animal as ''Aelurodon saevus''. It was recombined as ''Epicyon saevus'' by Baskin in 1980, Munthe in 1989, Voorhies in 1990, and Wang et al. 1999.

''Epicyon aelurodontoides'' existed from 9 to 7 million years ago and was named by X. Wang and others in 1999. This species was found south of the Young Brothers Ranch, Kansas.

Description

''Epicyon'' had a massive head and powerful jaws that were well adapted for bone-crushing, with enlarged fourth premolars like some hyenas, giving its skull a lion-like shape rather than having a skull similar in shape to that of a wolf; the adaptation would have allowed ''Epicyon'' to scavenge as well as hunt, giving it access to the nutritious marrow other contemporary carnivores couldn't access.

''E. haydeni'' was the largest known species of canid, it is estimated to have had a body length of , a shoulder height of and a body mass of approximately , with the largest known specimen weighing up to .

''E. saevus'' is estimated to have a shoulder height is up to and body mass is up to .

Paleobiology

Predatory behavior

The molars of ''E. haydeni'' were grindstone-like teeth that allow for a canid diet that includes both meat and plant and insects. The proportional size of an animal's molars is a great measure of the nutritional diversity of its diet. Based on fossilized feces and its robust teeth and jaw muscles it is believed to have consumed large amounts of bone and share a similar digestive tract to modern day hyenas due to their ability to break down bones. The deadly bite of a ''E. haydeni'' was delivered by the canine teeth, which are placed near the front of the upper and lower jaws, the shortening of the jaws can be an effective method for getting the canines closer to the mandibular condyle, thereby increasing the biting force.

The small clavicle, flexible back, and digitigrade posture of ''E. haydeni'' are all postcranial features shared with other canids and are likely adaptations designed to increase the animal's stride length. Examinations of the limb proportions and toughness of the skeleton suggests that ''E. haydeni'' was less cursorial than hyenas or modern wolves but more cursorial than other borophagine species like ''Aelurodon''. Unlike hyenas, ''E. haydeni'' must have used their rearmost lower premolar (p4) and upper carnassial (P4) to crack large bones (ibid.). Smaller bones and bone fragments were likely crushed with the carnassials and postcarnassial molars just as in extant canids. Due to its larger size and less gracile skeleton, ''E. haydeni'' was less cursorial and unable to run as long a distance as ''E. saevus,'' instead it relied on bursts of speed.

Predatory behavior for ''Epicyon'' heavily depends on the methods used. Schwab et al. (2019) found ''E. haydeni'' likely practiced pounce predation based on the anatomy of its bony labyrinth, while Figueirido et al. (2015) analysis on elbow morphology suggests ''E. haydeni'' was more of an ambush hunter. On the other hand, Martín-Serra et al. (2016) found ''E. haydeni'' practiced pursuit or pounce-pursuit predation, while ''E. saevus'' practiced pounce-pursuit predation based on forelimb analysis. Their analysis also suggests borophagines predatory behavior wasn’t equivalent to any living species.

Social behavior

Whether or not ''Epicyon'' was gregarious or solitary is unclear. Tomida and colleagues believed ''E. haydeni'' was gregarious as it was very prevalent in the fossil record, and was one of the most common carnivores in North America at the time. Valkenburgh and colleagues also argued gregariousness because their adaption to hunting large prey and canids not being able to grapple large prey like felids.

This interpretation was called into question by Ki Anderson, as craniodental and elbow joint morphology of borophaginaes resembled that of pantherine instead of recent canids, arguing that the latter isn’t a reliable indicator unsuitable modern analogues. The author of the paper admitted this isn’t enough to refute or support pack hunting among borophaginae as lions are capable of grappling prey, but they still hunt in social groups, showing the complexity of social behavior in carnivorans.

Paleoecology

Fossil specimens range from Florida to California and have been found in Nebraska, Montana, Kansas, Texas, New Mexico, Colorado, Oklahoma, Idaho, Oregon, Arizona within the United States, as well as in Alberta, Canada.

In North America, in places such as Coffee Ranch in Texas, ''Epicyon'' shared territory with the bear ''Agriotherium'' and the feliform '' Barbourofelis'', machairodont feline '' Amphimachairodus coloradensis'', and fellow canid '' Borophagus''. All of these animals were potential competitors that would have occasionally conflicted with ''Epicyon ''for food and territory. Prey for ''Epicyon'' included herbivores such as the camel '' Aepycamelus'', the pronghorn ''Cosoryx'', horses such as ''Neohipparion'' and ''Nannippus'', the peccary ''Prosthennops'', and the rhinoceroses such as '' Teleoceras'', all of which could provide a suitable meal through hunting or scavenging.

''Epicyon'' was one of the last of the borophagines, and shared its North American habitat with several other canids, including:
* '' Borophagus'' (Mya)
* '' Carpocyon'' from 20.4 to
* '' Paratomarctus'' from 16.3 to
* '' Aelurodon'' from 16.0 to
* '' Canis lepophagus'' from 10.3 to

References

*Alan Turner, "National Geographic: Prehistoric Mammals" (Washington, D.C.: Firecrest Books Ltd., 2004), pp. 112–114.

General references

*Xiaoming Wang, Richard H. Tedford, Mauricio Antón, ''Dogs: Their Fossil Relatives and Evolutionary History'', New York : Columbia University Press, 2008;

{{Taxonbar, from=Q2415423

Borophagines
Miocene canids
Miocene mammals of North America
Prehistoric carnivoran genera
Fossil taxa described in 1858