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 ...
of
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 ...
which includes the
gray fox
The gray fox (''Urocyon cinereoargenteus''), or grey fox, is an omnivorous mammal of the family Canidae, widespread throughout North America and Central America. This species and its only congener (biology), congener, the diminutive island fox ...
(''Urocyon cinereoargenteus'') and the island fox (''Urocyon littoralis''). These two fox species are found in the Western Hemisphere.
Whole genome sequencing
Whole genome sequencing (WGS), also known as full genome sequencing or just genome sequencing, is the process of determining the entirety of the DNA sequence of an organism's genome at a single time. This entails sequencing all of an organism's ...
indicates that ''Urocyon'' is the most basal genus of the living canids. 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
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58
Extinct species
Cozumel fox
The Cozumel fox is a critically endangered small gray fox found on the island of Cozumel,
Mexico
Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
. The last reported sighting was in 2001, but surveys focusing on this species have not yet been carried out. In September 2023, a live Cozumel fox was rescued from a road and subsequently released.
The Cozumel fox has not been scientifically described, but is a
dwarf
Dwarf, dwarfs or dwarves may refer to:
Common uses
*Dwarf (folklore), a supernatural being from Germanic folklore
* Dwarf, a human or animal with dwarfism
Arts, entertainment, and media Fictional entities
* Dwarf (''Dungeons & Dragons''), a sh ...
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.
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.