''Hesperocyon'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

canids Canidae (; from Latin, ''canis'', "dog") is a biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamilies: the Caninae, and the extinct Borophaginae ...

(subfamily

Hesperocyoninae The extinct Hesperocyoninae are one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Borophaginae and extant Caninae. Taxonomic history Hesperocyoninae are basal canids that gave rise to the ...

, family

Canidae Canidae (; from Latin, ''canis'', "dog") is a family (biology), biological family of caniform carnivorans, constituting a clade. A member of this family is also called a canid (). The family includes three subfamily, subfamilies: the Caninae, a ...

) that was endemic to

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

, ranging from southern

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

. It appeared during the

Uintan The Uintan North American Stage is the North American faunal stage, typically set from 46,200,000 to 42,000,000 years before present lasting 4.2 million years. The Uintan Stage is a key part of the North American land mammal age, North American Lan ...

age, – Bridgerian age (NALMA) of the Mid-

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

– 42.5 Ma to 31.0 Ma. ( AEO). ''Hesperocyon'' existed for approximately .

Taxonomy

''Hesperocyon'' was assigned to Borophagini by Wang et al. in 1999 and was the earliest of the canids to evolve after the

Caniformia Caniformia is a suborder within the order Carnivora consisting of "dog-like" carnivorans. They include Canidae, dogs (Wolf, wolves, foxes, etc.), bears, raccoons, and Mustelidae, mustelids. The Pinnipedia (pinniped, seals, walruses and sea lions) ...

Feliformia Feliformia is a suborder within the order Carnivora consisting of "cat-like" carnivorans, including Felidae, cats (large and small), hyenas, mongooses, viverrids, and related taxa. Feliformia stands in contrast to the other suborder of Carnivora, ...

split some 42 million years ago.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

evidence dates ''Hesperocyon gregarius'' to at least 37 mya, but the oldest ''Hesperocyon'' has been dated at 39.74 mya from the

Duchesnean The Duchesnean North American Stage on the geologic timescale is a North American Land Mammal Age (NALMA), with an age from 42 to 38 million years BP, representing . It falls within the Eocene epoch. The Duchesnean is preceded by the Uintan and f ...

North American land mammal age The North American land mammal ages (NALMA) establishes a geologic timescale for North American fauna beginning during the Late Cretaceous and continuing through to the present. These periods are referred to as ages or intervals (or stages when ref ...

. The

subfamily Hesperocyoninae probably arose out of ''Hesperocyon'' to become the first of the three great dogs groups: Hesperocyoninae (~40–30 Ma), Borophaginae (~36–2 Ma), and the

Caninae Caninae (whose members are known as canines () is the only living subfamily within Canidae, alongside the extinct Borophaginae and Hesperocyoninae. They first appeared in North America, during the Oligocene around 35 million years ago, subsequent ...

lineage that led to the present-day canids (including

grey wolves The wolf (''Canis lupus''; : wolves), also known as the grey wolf or gray wolf, is a canine native to Eurasia and North America. More than thirty subspecies of ''Canis lupus'' have been recognized, including the dog and dingo, though grey ...

fox Foxes are small-to-medium-sized omnivorous mammals belonging to several genera of the family Canidae. They have a flattened skull; upright, triangular ears; a pointed, slightly upturned snout; and a long, bushy tail ("brush"). Twelve species ...

es,

coyote The coyote (''Canis latrans''), also known as the American jackal, prairie wolf, or brush wolf, is a species of canis, canine native to North America. It is smaller than its close relative, the Wolf, gray wolf, and slightly smaller than the c ...

jackal Jackals are Canidae, canids native to Africa and Eurasia. While the word has historically been used for many canines of the subtribe Canina (subtribe), canina, in modern use it most commonly refers to three species: the closely related black-b ...

s and

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers. ...

s). At least 28 known species of Hesperocyoninae evolved out of ''Hesperocyon'', including those in the following five genera: '' Ectopocynus'' (32–19 mya), '' Osbornodon'' (32–18 mya), '' Paraenhydrocyon'' (20–25 mya), '' Mesocyon'' (31–15 mya) and '' Enhydrocyon'' (31–15 mya).

Evolution

This genus of primitive canids is the ancestor of all later canids.

Morphology

This early, canine looked more like a

civet A civet () is a small, lean, mostly nocturnal mammal native to tropical Asia and Africa, especially the tropical forests. The term ''civet'' applies to over a dozen different species, mostly from the family Viverridae. Most of the species's div ...

or a small

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...

. Its body and

tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...

were long and flexible, while its limbs were weak and short. Still, the build of its

ossicles The ossicles (also called auditory ossicles) are three irregular bones in the middle ear of humans and other mammals, and are among the smallest bones in the human body. Although the term "ossicle" literally means "tiny bone" (from Latin ''ossi ...

and distribution of its

teeth A tooth (: teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

showed it was a canid. It may have been an

omnivore An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize t ...

—unlike the

hypercarnivorous A hypercarnivore is an animal that has a diet that is more than 70% meat, either via active predation or by scavenging. The remaining non-meat diet may consist of non-animal foods such as fungi, fruits or other plant material. Some extant example ...

Borophaginae The extinct Borophaginae form one of three subfamilies found within the canid family. The other two canid subfamilies are the extinct Hesperocyoninae and extant Caninae. Borophaginae, called "bone-crushing dogs", were endemic to North America d ...

that later split from this canid lineage. Unlike modern canids, ''Hesperocyon'' had five fingers and toes and a dew claw deeply set enough to suggest tree climbing capabilities. Hesperocyon skull Smithsonian

Fossil record

The oldest fossil evidence was recovered from

Saskatchewan Saskatchewan is a Provinces and territories of Canada, province in Western Canada. It is bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and to the south by the ...

dating from 42.5 mya to 31.0 Ma. The youngest fossil was recovered from the Dog Jaw Butte site,

Goshen County, Wyoming Goshen County (, ) is a county in the U.S. state of Wyoming. As of the 2020 United States census, the population was 12,498. Its county seat is Torrington. The eastern boundary of the County borders the Nebraska state line. Goshen County prod ...

dating to the

Arikareean The Arikareean North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 30,600,000 to 20,800,000 years BP, a period of . It is usuall ...

age (NALMA) of the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

and

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

42.5 mya—31.0 Ma. (AEO).Paleobiology Database
Collection 17492, Dog Jaw Butte site,

. Authorized and entered by Dr. John Alroy, March 26, 1995.

References

{{Taxonbar, from=Q1947861 Hesperocyonines Eocene carnivorans Oligocene canids Transitional fossils Prehistoric carnivoran genera Paleogene mammals of North America Fossil taxa described in 1890