Epicyon haydeni

This canine had an extremely strong jaw that could crush bones!

The Epicyon haydeni was a species of dog that lived from the Early Miocene to the Late Miocene. This was around 5 to 20 million years ago. It belonged to the sub-family of Borophaginae or “bone-crushing dogs” and weighed about 200 to 300 lbs. Fossils of this species of Epicyon were found in several regions all over North America.

Scientific Name

Epicyon haydeni

The word Epicyon means “more than a dog.” It was named by Joseph Leidy first as a subgenus Aelurodon haydeni. Later, in the 1980s, paleontologist Baskin named it Epicyon haydeni. The species was named after a known geologist  Dr. Ferdinand Vandeveer Hayden. Alternate scientific names of the species over the years include:

Canis haydeni; Aelurodon haydeni; Aelurodon haydeni validus; Tephrocyon mortifer; Aelurodon aphobus; Tomarctus mortifer; Osteoborus validus; Osteoborus ricardoensis; Aelurodon mortifer; Epicyon validus.

Unlike most dogs that belong to the Caninae family, they belong to a unique family of Borophagina dogs. These dogs crushed the bones of their prey.

Description & Size

Known as one of the largest species of all canines, the Epicyon Haydeni had a body length of about 7-10 feet and a shoulder height of 35 inches. It weighed about 200-300 lbs, with the largest known specimen weighing 370 lbs.

Similar to modern day dogs, the animal had grinding teeth, which gives scientists the impression that the Epicyon haydeni was omnivorous. Based on the fossilized specimen and their strong jaw muscles, it is concluded that their digestive system was probably strong enough to grind the bones of other animals – a unique characteristic of this dog. 

Alongside their grinding teeth, they also had canine teeth on the front of their upper and lower jaws. The overall distribution of their teeth was distinct compared to other canines of the era and showed that while the animal was omnivorous, its diet was largely based (more than 70 percent) on large herbivorous animals, making it hypercarnivorous. Their teeth also showed signs of heavy dental erosion, probably because these animals crushed the bones of their prey.

The animal had a small clavicle and flexible limbs. Based on their legs and the body proportion of the fossils, they were probably less cursorial and unable to run very long distances. Instead, they ran in short bursts of speed.

Diet – What Did the Epicyon haydeni Eat?

The Epicyon haydeni was an omnivorous species that fed on plants, insects, and herbivorous animals. They were hypercarnivorous which means that they fed 70 percent on meat. Their prey likely included the camel relative Aepycamelus, the deer species Cosoryx, Neohipparion, Prosthennops (a warthog species), and Teleoceras (an ancient rhinoceroses) – all animals found within their habitat in what is now North America.

However, it must be noted that the answer to the question “what did the Epicyon haydeni eat?” is primarily based on speculation and an analysis of the animal’s habitat and teeth.

Habitat – When And Where It Lived

Epicyon haydeni fossils were found in various areas of modern day US and Canada in particular. They were very widespread species ranging across the entire United State fossils have been found in Florida, Montana, Texas, New Mexico, Nebraska, Colorado, Idaho, Oregon, Oklahoma, and Arizona. In Canada, fossils were found in Alberta. So their general habitat was terrestrial lands grazed by herbivorous animals.

They lived about 5 to 20 million years ago during the Early Miocene to the Hemphillian of the Late Miocene period – the age of North American land animals.

Threats And Predators

The Epicyon haydeni was a large apex predator that did not likely have many predators or its own. But, In several areas of North America, the habitat of the Epicyon haydeni was co-inhabited by the bear Agriotherium, the feliform Barbourofelis, the machairodont cat Amphimachairodus coloradensis, and fellow canid Borophagus. All these animals could have been possible competitors and predators. Other similar species also competed with the Epicyon haydeni for food and mates.

Discoveries and Fossils – Where It Was Found

Fossils of the Epicyon haydeni were primarily found in the American states of Texas, Nebraska, Montana, New Mexico, Oklahoma, California, Arizona, Kansas, Colorado, Oklahoma, Idaho, and Oregon. Some Florida fossil sites include McGehee Farm, Fort Green Mine, Waccasassa River 6, and Silver City Mine.

Extinction – When Did It Die Out?

It is thought that these dogs went extinct due to the arrival of the big cats. The Epicyon haydeni were generally slow animals that hunted by running in bursts. On the contrary, one of the species of big cats, the sabertooth cats, were much faster hunters that preyed on the same animals as the Epicyon haydeni did. So, likely the Epicyon haydeni’s prey was hunted by these big cats. This eventually led to their slow death from lack of food. As the animal was not getting a proper diet, they couldn’t breed either, which ultimately led to their extinction.

Similar Animals To The Epicyon Haydeni

• Present-day hyenas – They have the same widened palate, shorter rostrum, and a dome-shaped forehead. It is thought that some hyenas might also be descendants of the Epicyon haydeni.
• Epicyon saevus – This species existed between 5-16 million years ago, so it had an overlap with the Epicyon haydeni. The structure of its body was similar to the Epicyon haydeni, except it weighed less at 150-200 lbs and had a shorter shoulder height at 22 inches.
• Epicyon aelurodontoides – Found in Kansas, this species also lived in the habitat of the Epicyon haydeni and lived 5-10 million years ago. This species could’ve been a possible mate for the Epicyon haydeni and a competitor for food.

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