They were previously believed to belong to the much larger genus Spermophilus, but DNA sequencing of the cytochrome b gene showed that this group was paraphyletic to the prairie dogs and marmots,[2] and could therefore no longer be retained as a single genus.

[3] All but two species are native to the northern and western parts of North America, from California and Minnesota through the north-western United States and western Canada; the Arctic ground squirrel inhabits Arctic terrain on both sides of the Bering Strait, while the long-tailed ground squirrel is exclusively found in Asia.

The name of the genus is said to be derived from the Latin uro, meaning "tail" and citellus for "ground squirrel".

[3] The proper word for "tail" in classical Latin is cauda.

[4] Oura (οὐρά) is the ancient Greek word for "tail".