Wandering About in North America During the Miocene: Certainty an Ill-Advised Endeavor.

Greetings. Canidae is a biological family of dog-like carnivorans, colloquially referred to as dogs. Members of the family are often referred to as canids. The family includes three subfamilies: the Caninae, and the extinct Borophaginae and Hesperocyoninae. The Caninae are known as canines, and include domestic dogs, wolves, coyotes, foxes, jackals and other species.

Epicyon is an extinct genus of the subfamily Borophaginae, which was native to the North American continent. The genus existed for about 15 million years during the Miocene Epoch. Epicyon haydeni is the largest known species, and is the largest known canid of all time, with adults of the species reaching 2.4 meters in length and approximately 125 kilograms in body mass. The largest fossilized humerus recovered so far belonged to an adult individual weighing 170 kilograms. 

Epicyon haydeni existed from 20.6 till' approximately 5.3 million years ago. The molars of E. haydeni were grindstone-like teeth that allowed for a diverse diet that included meat, insects, and plant matter. 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, with the species sharing a digestive tract similar to modern-day hyenas, known for their ability to crush and digest bone. The deadly bite of a E. haydeni was delivered by the canine teeth, which were placed near the front of the upper and lower jaws. The shortening of the jaws in E. haydeni was highly effective for getting the canines closer to the mandibular condyle, thereby increasing the animal's biting force.

Epicyon haydeni's small clavicle, flexible back, and digitigrade posture are all postcranial features shared with other canids and are likely evolutionary adaptations designed to increase the animal's length of stride. Scientific examinations of the limb proportions and toughness have demonstrated that E. haydeni's skeleton was less cursorial than modern-day hyenas or wolves but more cursorial than other borophagine species like Aelurodon. Unlike today's hyenas, E. haydeni must have used their rearmost lower premolar and upper carnassial to crack large bones. Smaller bones and bone fragments were likely crushed with the carnassials and postcarnassial molars just as in extant canids. Due to its massive size and heavier, less gracile skeleton, E. haydeni was less cursorial and incapable of running long distances, instead relying on bursts of speed and social hunting strategies.

Fossilized specimens have been found all across North America, in Florida, California, Nebraska, Montana, Kansas, Texas, New Mexico, Colorado, Oklahoma, Idaho, Oregon, Arizona within the United States, as well as in Alberta, Canada.

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