The three species of New World flying squirrels, genus Glaucomys, are the only species of flying squirrel found in North America.
 They are distributed from Alaska to Honduras.
 They are similar in many ways to the Eurasian flying squirrels in the genus "Pteromys".
 Two species of New World flying squirrels can be easily distinguished on the basis of size and ventral pelage.
 Northern flying squirrels, "Glaucomys sabrinus" are larger and have belly hair that is dark at the base and white at the tip.
 Southern flying squirrels, "Glaucomys volans", are smaller and have belly hairs that are completely white.
 Humboldt's flying squirrel is more difficult to distinguish from the northern flying squirrel where their ranges overlap.
 In fact, they were considered conspecific.
 The Humboldt's flying squirrel is considered a cryptic species.
 They are generally smaller and darker than northern flying squirrels.
The Japanese dwarf flying squirrel ("Pteromys momonga"; Japanese: ニホンモモンガ; Hepburn: "Nihon momonga") is one of two species of Old World flying squirrels.
 It is native to Japan where it inhabits sub-alpine forests and boreal evergreen forests on Honshu and Kyushu islands.
 It grows to a length of 20 cm and has a membrane connecting its wrists and ankles which enables it to glide from tree to tree.
 During the day this squirrel hides in a hole, usually in a coniferous tree, emerging at night to feed on buds, leaves, bark, fruits and seeds.
 This squirrel faces no particular threats, has a wide range and is relatively common, and the International Union for Conservation of Nature lists it as a "least-concern species".
The Basilan flying squirrel (Philippines flying squirrel or Mindanao flying squirrel ) ("Petinomys crinitus") is a species of rodent in the family Sciuridae.
 It is endemic to the Philippines.
 It is often confused with mindanao flying squirrel (Petinomys mindanensis)
The Japanese giant flying squirrel (ムササビ , musasabi , "Petaurista leucogenys") is a species of flying squirrel, one of two species of Old World flying squirrels.
 It is native to Japan where is inhabits sub-alpine forests and boreal evergreen forests on Honshu, Shikoku and Kyushu islands.
 It grows to a head-and-body length of 50 cm with a tail nearly as long again, and has a membrane connecting its wrists and ankles which enables it to glide from tree to tree.
 It feeds mainly on fruits and seeds.
 It breeds once a year in the autumn, with one or two young being born in its den.
 This squirrel faces no particular threats, has a wide range and is relatively common, and the International Union for Conservation of Nature lists it as being of "least concern".
Commonly referred to as simply the Old World flying squirrels, the genus Pteromys is distributed across temperate Eurasia, Korean Peninsula and Japan.
 Although there are a host of flying squirrel genera in Asia (particularly southern Asia), "Pteromys" is the only one present in Europe.
Travancore flying squirrel ("Petinomys fuscocapillus"), also known as the small flying squirrel, is a flying squirrel found in South India and Sri Lanka.
 Travancore flying squirrels were thought to be extinct but were rediscovered in 1989 after a gap of 100 years in Kerala.
 It was rediscovered in Sri Lanka after 78 years.
 The animals were reported only in wet and intermediate zones of the island, and had a few sightings in the Sinharaja Forest Reserve.
The Prince of Wales flying squirrel, "Glaucomys sabrinus griseifrons", is a subspecies of the northern flying squirrel.
 "Glaucomys sabrinus griseifrons" is endemic to Prince of Wales Island in Alaska and has a unique coloration compared to other subspecies of northern flying squirrel.
 It is whiter on the ventral side, darker on the dorsal side, and the head/neck area tend to be more gray than other subspecies.
 This subspecies is genetically distinct from the northern flying squirrel from evidence found in mitochondrial DNA and microsatelite data.
 Adults are usually around 25-37 centimeters in length and 110-230 grams in weight.
 This subspecies is often considered a keystone species in the Southeastern Alaska area because it consumes and disperses conifer seeds and fungal spores into areas with little vegetation and sites of disturbance.
 The released fungi spores aid in the absorption of nutrients by plants and speed up regrowth in these areas.
Humboldt's flying squirrel ("Glaucomys oregonensis") is one of three species of the genus "Glaucomys", the only flying squirrels found in North America.
 Using genetic analyses, Arbogast et al. (2017) showed that Humboldt's flying squirrel, previously thought to be conspecific with the northern flying squirrel, was actually a distinct species.
 Humboldt's flying squirrels are found in coniferous and mixed coniferous forests from southern British Columbia to southern California.
 They are similar in appearance to the northern flying squirrel, however, they are generally smaller and have darker pelage.
 They are good gliders but clumsy walkers on the ground.
 They feed on a variety of plant material as well as tree sap, fungi, insects, carrion, bird eggs and nestlings.
 They mostly breed once a year in a cavity lined with lichen or other soft material.
 Unlike most members of their family, flying squirrels are strictly nocturnal.
The Siberian flying squirrel ("Pteromys volans") is an Old World flying squirrel with a range from the Baltic Sea in the west to the Pacific coast in the east.
 It is the only species of flying squirrel found in Europe.
 It is considered vulnerable within the European Union where it is found only in Finland, Estonia and Latvia.
The red giant flying squirrel or common giant flying squirrel ("Petaurista petaurista") is a species of flying squirrel, found in northern South Asia, southern China and Southeast Asia.
 It is a dark red colour with black extremities and can grow to a head-and-body length of 42 cm .
 The tail is long and provides stability when it glides between trees.
 It is nocturnal, feeding mainly on leaves, fruits and nuts, and occasionally insects.
 This squirrel faces no particular threats apart from ongoing destruction of suitable habitat.
 It has a wide range and is relatively common, and the International Union for Conservation of Nature lists it as a "least-concern species".

Question: Which os the only species of the Old World flying squirrel found in Europe?
Answer: Siberian flying squirrel