Urocyon

Urocyon (Greek: "tailed dog"^[7]) is a genus of Canidae which includes the gray fox (Urocyon cinereoargenteus) and the island fox (Urocyon littoralis).^[1] These two fox species are found in the Western Hemisphere. Whole genome sequencing indicates that Urocyon is the most basal genus of the living canids.^[8] Fossils of what is believed to be the ancestor of the gray fox, Urocyon progressus, have been found in Kansas and date to the Upper Pliocene,^[9] with some undescribed specimens dating even older.^[10]

Urocyon[1] Temporal range: 10.3–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N [2]
Gray and island fox
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	Canidae
Subfamily:	Caninae
Genus:	Urocyon Baird, 1857[3]
Type species
Canis virginianus[4] Schreber, 1774[5]
Species
U. cinereoargenteus (Schreber), 1774 U. littoralis Baird, 1857 † U. citrinus Tedford, Wang & Taylor (2009)[6] † U. galushai Tedford, Wang & Taylor (2009)[6] † U. minicephalus Martin, 1974 † U. progressus Stevens, 1965 † U. webbi Tedford, Wang & Taylor (2009)[6]

Extant species

Genus Urocyon – Baird, 1857 – two species

Common name	Scientific name and subspecies	Range	Size and ecology	IUCN status and estimated population
Gray fox	Urocyon cinereoargenteus (Schreber, 1775)	Southern half of North America from southern Canada to the northern part of South America (Venezuela and Colombia), excluding the mountains of northwestern United States	Size: Habitat: Diet:	LC
Island fox	Urocyon littoralis (Baird, 1857) Six subspecies U. l. littoralis (the nominate subspecies) of San Miguel Island, U. l. dickeyi of San Nicolas Island, U. l. catalinae of Santa Catalina Island, U. l. clementae of San Clemente Island, U. l. santacruzae of Santa Cruz Island, and U. l. santarosae of Santa Rosa Island.	Channel Islands (off the coast of Southern California)	Size: Habitat: Diet:	NT

Skull cast of U. minicephalus, Florida Museum of Natural History

Extinct species

Species name	Type specimen era and location[6]
U. citrinus	Tedford et al., 2009. Early Irvingtonian, Citrus County, Florida.
U. galushai	Tedford et al., 2009. Late Blancan, San Simon Valley, Graham County, Arizona.
U. minicephalus	Martin, 1974. Late Irvingtonian, Sumter County, Florida.
U. progressus	Stevens, 1965. Early Blancan, Meade County, Kansas. A later review found that the material represents Urocyon, but because of its fragmentary nature cannot be diagnosed as to species.[6]
U. webbi	Tedford et al., 2009. Middle Hemphillian, Citrus County, Florida.

Cozumel fox

The Cozumel fox is a critically endangered small gray fox found on the island of Cozumel, Mexico. The last reported sighting was in 2001, but surveys focusing on this species have not yet been carried out.^[11] In September 2023, a live Cozumel fox was rescued from a road and subsequently released.^[12][13]

The Cozumel fox has not been scientifically described, but is a dwarf form as is the island fox, but is slightly larger than the island fox, being up to three-quarters the size of the gray fox. No skins or complete skulls of the Cozumel fox exist in any museum exhibitions, so scientists have mainly examined sub-fossils collected during archaeological excavations of Mayan civilizations who inhabited the island about 1,500–500 years ago. Upon evaluating bones from about 12 adult individuals, scientists have concluded that the Cozumel fox is extremely small – approximately 60-80% the body size of other mainland specimens.^[14]

The fox had been isolated on the island of Cozumel for at least 5,000 years, and probably far longer. This would indicate that Urocyon had colonized the island before the first arrival of humans there.^[14]