Epicyon

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in biology, Epicyonis ("more than a dog")  an extinct genus of the Borophaginae Subtribes of canids native to North America. Possibly the largest prehistoric dog that ever lived, Epicyon was a true "canid," belonging to the same general family as wolves, hyenas and modern dogs—and was thus a different beast altogether from the non-canid "creodont" mammals (typified by the giant Sarkastodon) that ruled the North American plains for millions of years before the Miocene epoch. The largest species of Epicyon weighed in the neighborhood of 200 to 300 pounds—as much as, or more than, a full-grown human--and it possessed unusually powerful jaws and teeth, which made its head look more like that of a big cat than a dog or wolf. However, paleontologists don't know much about Epicyon's feeding habits: this megafauna mammal may have hunted alone or in packs, and it may even have subsisted exclusively on already-dead carcasses, like a modern hyena.

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.

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.

In North America, in places such as Coffee Ranch in Texas, Epicyon shared territory with the bear Agriotherium and the feliform Barbourofelis, machairodont cat 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 is known by three species, all of which were discovered in western North America in the course of the 19th and 20th centuries. The lightest variant, Epicyon saevus, was named by the famous American paleontologist Joseph Leidy, and for a time was classified as a species of Aelurodon; adults only weighed about 100 pounds fully grown. E. haydeni was also named by Leidy, and has been synonymized not only with Aelurodon, but with the even more obscure Osteoborus and Tephrocyon as well; this was the largest Epicyon species, weighing more than 300 pounds. The most recent addition to the Epicyon family, E. aelurodontoides, was discovered in Kansas in 1999; you can tell by its species name that it was also close kin to Aelurodon!