The difficulties of identifying flying squirrels (Sciuridae: Pteromyini) in the fossil record
Richard W. Thorington, Jr, Chad E. Schennum, Lindsay A. Pappas, and Diane Pitassy, Journal of Vertebrate Paleontology, 2005, 25(4):950-961
Two problems are examined in this paper: (1) the identification of flying squirrels in the fossil record by means of their teeth; and (2) the identification of features of the limbs that indicate that the animals were gliders. Dental features vary widely among flying squirrels and among other squirrels, and a thorough survey demonstrates that most features that have been used to distinguish fossil flying squirrels are also found in some tree squirrels. A review of the descriptions of fossil flying squirrels reveals few convincing arguments that these animals actually belong to the Pteromyini and none to support the hypothesis that they were gliding animals. Recent flying squirrels exhibit a number of distinguishing morphological features in their carpal and tarsal bones and at the proximal and distal ends of their long bones. Some of these morphological structures are obligatory features required for gliding locomotion in squirrels and hence are diagnostic of flying squirrels.