Urocyon

Urocyon (Greek: "tailed dog"<ref>Urocyon.</ref>) is a genus of Canidae which includes the gray fox (Urocyon cinereoargenteus) and the island fox (Urocyon littoralis).<ref name=Wozencraft2005/> 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.<ref name=Lindblad-Toh2005/> 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,<ref name=Stevens1965/> with some undescribed specimens dating even older.<ref name=PrevostiRincón2007/>

Extant species

File:Urocyon minicephalus FLMNH.jpg

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

Extinct species

Species name	Type specimen era and location<ref name=Tedford2009/>
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.<ref name=Tedford2009/>
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.<ref>Template:Cite journal</ref> In September 2023, a live Cozumel fox was rescued from a road and subsequently released.<ref>Template:Cite web</ref><ref>Template:Cite web</ref>

The Cozumel fox has not been scientifically described, but is a dwarf form, like the island fox. Compared to the island fox, however, it is slightly larger, 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.<ref name=Gompper-Petrites-Lyman-2006>Template:Cite journal</ref>

The fox had been isolated on Cozumel for at least 5,000 years, and probably far longer. These dates would indicate that Urocyon had colonized the island before the first arrival of humans there.<ref name=Gompper-Petrites-Lyman-2006/>