Mouse-like hamsters are a group of small rodents found in Syria, Azerbaijan, Iran, Turkmenistan, Afghanistan, and Pakistan. They are found in rocky outcrops and semi-mountainous area in desert regions.
The mouse-like hamsters are not true hamsters, but represent an early split from the rest of the mouse-like rodents. They were once thought to be hamsters based on the shape of their molars, but they lack the cheek pouches, sebaceous flank glands, and short tail of the true hamsters. The closest relatives of mouse-like hamsters may be the fossil Cricetodontidae. Because of their seemingly early break from the rest of the mouse-like rodents, mouse-like hamsters have been placed in a family of their own, Calomyscidae, and have been referred to as living fossils.
All members of this genus were once considered part of the same species, Calomyscus bailwardi, but they are now referred to as separate species due to major differences in chromosome number, skull measurements, and other features.
In Europe, a species of Calomyscus is available as a pet. They are labelled Calomyscus bailwardi mystax or Calomyscus bailwardi, and probably represent either C. mystax or C. elburzensis. They are only available from dedicated breeders, not pet shops, so they are usually limited to serious rodent fans.
Mouse-like hamsters hold the record for maximum life span among muroid rodents (Volf, 2003). They have been recorded as living 9 years, 3 months and 18 days in captivity. They regularly live over 4 years in captivity. The next closest lifespan among muroids is 7 years, 8 months among the better studied Canyon Mouse, Peromyscus crinitus. This and their low reproductive output suggests that mouse-like hamsters are more similar in life-history traits to much larger rodents such as sciurids and hystricognaths who can both live over 10 years in captivity.