''Hesperocyon'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

canids Canidae (; from Latin, ''canis'', " dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found within ...

(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 th ...

, family

Canidae Canidae (; from Latin, ''canis'', "dog") is a biological family of dog-like carnivorans, colloquially referred to as dogs, and constitutes a clade. A member of this family is also called a canid (). There are three subfamilies found within th ...

) that was endemic to

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, ranging from southern

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

. It appeared during the

Uintan The Uintan 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 46,200,000 to 42,000,000 years BP lasting . It falls within the ...

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

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

– 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-

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

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 preserved ...

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 ...

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 The Caninae, known as canines, are one of three subfamily, subfamilies found within the Canidae, canid family. The other two canid subfamilies are the extinct Borophaginae and Hesperocyoninae. The Caninae includes all living canids and their most ...

lineage that led to the present-day canids (including

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

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 (or ''brush''). Twelve sp ...

es,

coyote The coyote (''Canis latrans'') is a species of canis, canine native to North America. It is smaller than its close relative, the wolf, and slightly smaller than the closely related eastern wolf and red wolf. It fills much of the same ecologica ...

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

s and

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the wolf. Also called the domestic dog, it is derived from the extinct Pleistocene wolf, and the modern wolf is the dog's nearest living relative. Do ...

s). At least 28 known species of Hesperocyoninae evolved out of ''Hesperocyon'', including those in the following five genera: '' Ectopocynus'' (32–19 mya), ''

Osbornodon ''Osbornodon'' (" Osborn's tooth") is an extinct genus of canid that were endemic to North America and which lived from the Oligocene to the Early Miocene, 33.9—15.97 Ma ( AEO), existing for approximately . Paraenhydrocyon'' (20–25 mya), ''

Mesocyon ''Mesocyon'' ("middle dog") is an extinct genus of the Hesperocyoninae subfamily of early canids native to North America. It lived from the Oligocene to Early Miocene, 30.3—20.3 Annum, Ma, existing for approximately . Fossils are known from Ore ...

'' (31–15 mya) and ''

Enhydrocyon ''Enhydrocyon'' is an extinct genus of bone crushing Canidae, canid which inhabited North America during the Oligocene and Early Miocene, 30.8—20.4 Annum, Ma, existing for approximately . ''Enhydrocyon'' dentition suggests this animal was a h ...

'' (31–15 mya).

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 diversity ...

or a small

raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the common raccoon to distinguish it from other species, is a mammal native to North America. It is the largest of the procyonid family, having a body length of , and a body weight of ...

. Its body and

tail The tail is the section at the rear end of certain kinds of animals’ bodies; in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, r ...

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 bones in either middle ear that are among the smallest bones in the human body. They serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea). The absence of the auditory ...

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 has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

—unlike the

hypercarnivorous A hypercarnivore is an animal which 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 exampl ...

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 du ...

that later split from this canid lineage. 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, western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on t ...

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 produces m ...

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 of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

and

Miocene The Miocene ( ) is the first 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 means "less recen ...

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 carnivorans Transitional fossils Prehistoric carnivoran genera Paleogene mammals of North America Fossil taxa described in 1890