Tree squirrels are the members of the squirrel family (Sciuridae) commonly just referred to as "squirrels". They include more than 100 arboreal species native to all continents except Antarctica and Oceania.
Eastern gray squirrel (Sciurus carolinensis)
Prevost's squirrel (Callosciurus prevostii)
Indian palm squirrel (Funambulus palmarum)
American red squirrel (Tamiasciurus hudsonicus)
Squirrels are members of the family Sciuridae, a family that includes small or medium-sized rodents. The squirrel family includes tree squirrels, ground squirrels, and flying squirrels. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known fossilized squirrels date from the Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and to the dormice.
Squirrel
Reaching out for food on a garden bird feeder, this squirrel can rotate its hind feet, allowing it to descend a tree headfirst.
Skull of an Oriental giant squirrel (genus Ratufa)—note the classic sciuromorphous shape of the anterior zygomatic region.
Squirrel in sunlight