Dog family’s fossil story starts in Eocene North America
Canidae—the dog family—covers wolves to foxes across every continent but Antarctica. Living canids sit in subfamily Caninae beside extinct Hesperocyoninae and Borophaginae branches. Cat-like and dog-like carnivorans split about 45–42 million years ago; canids appear in Late Eocene North America before reaching Eurasia later.
Some 37 species make up the family, from the long-legged maned wolf to the stubby bush dog, and from a gray wolf about two metres long to a fennec fox of 24 cm. Most share long muzzles, upright ears, long legs, bushy tails and teeth built both to crack bone and slice meat. They live in forests, tundra, savanna and desert, reaching every continent except Antarctica, some on their own and some alongside people.
Canids tend to be social, living in family groups that cooperate. Usually only the breeding pair in a group has young, raising one litter a year in an underground den, and members keep in touch by scent marks and calls. The domestic dog grew out of a partnership with Upper Paleolithic humans and is now among the most widely kept animals on Earth.
Carnivorans spread after the dinosaurs vanished 66 million years ago and split into dog-like and cat-like branches. By 40 million years ago the first recognisable canid, Prohesperocyon wilsoni, lived in what is now southwest Texas. It had lost its upper third molar, a step toward a shearing bite, had an enlarged bony chamber around the middle ear, and walked on close-set parallel toes unlike a bear's splayed digits.
The family soon divided into three subfamilies. Hesperocyonines lasted until about 15 million years ago and the borophagines also died out; both lineages grew larger over time, and some became meat specialists prone to extinction. Only the Caninae survive. Canids stayed in North America until reaching Eurasia in the Late Miocene and South America in the Late Pliocene. Today, heavy gene flow between some populations produces broad hybrid zones.
Source: Canidae
