Largest wild canid ever
Epicyon haydeni
95 cm / 75 kg dimension(s)
United States ()

The biggest wild canid (member of the dog family) of all time was Epicyon haydeni, found across vast parts of North America from Montana and Nebraska to Florida and New Mexico between 7 and 10 million years ago. Fossil remains found in Kansas indicate a predator that stood circa 95 cm (3 ft 1 in) at the shoulder and weighed up to 75 kg (165 lb), rivalling a black bear in size and surpassing any other wild dog. Epicyon was a borophagine, a completely extinct group of canids endemic to North America which first appeared 34 million years ago.

The canid family are a diverse group of carnivorans today both in number of species and their lifestyles, ranging from the omnivorous, occasionally tree-climbing Asiatic raccoon dogs (genus Nyctereutes) to the crab-eating fox (Cerdocyon thous) of the South American jungles.

Being one of the most evolutionarily advanced borophagines, Epicyon sported a stout, box-like head somewhat like a bulldog, with robust, bolt cutter-like dentition like today’s hyenas, capable of crunching through bones. The independent, parallel emergence of such dental structure among hyenas of the Old World and North American borophagines over this period is a classic case of convergent evolution, whereby distantly related animals in distant evolutionary contexts evolve similar features for a similar function.

Canids originated in North America over 40 million years ago as nondescript little carnivores no larger than 1 kg (3 lb 3 oz). Through a vast evolutionary history, the only canids to have successfully dispersed and occupy other land masses were the canines (Caninae), the group including all modern dogs. The largest wild canine was the Ice Age North American dire wolf (Aenocyon dirus), with a shoulder height of 77 cm (2 ft 6 in) and weight of 68 kg (150 lb); a modern wolf (Canis lupus, the largest extant wild canid), by contrast, weighs about 45 kg (99 lb) on average. Long thought to be an offshoot of wolf evolution that made its evolutionary "homecoming" to North America, after "true" wolves first emerged in Northern Eurasia at about 2 million years ago, a recent ancient DNA study threw this age-old perception out of the window. The 2021 study concludes that the dire wolf was in fact the last of its kind, the end-member of an obscure canine lineage that remained endemic to North America and branched off its shared common ancestor with the wolves and jackals of the Old World 5.7 million years ago. The extraordinary similarities of its skeletal anatomy to the Eurasian true wolves is yet another notable example of convergent evolution in the history of canids.

Among domestic canines, even larger examples can be found, especially in two particular breeds: the Great Dane and the Irish wolfhound. The largest dog ever confirmed by Guinness World Records was a Great Dane named Zeus from Michigan, USA, who stood 111.8 cm (3 ft 8 in) at the shoulder and weighed 70.3 kg (145 lb) when measured on 4 October 2011.