Evolution and systematics

Anomaluridae is an exceedingly ancient rodent family, with a lineage extending back some 30 million years (late Eocene). Formerly much more diverse, some 20 fossil genera have been identified. The external resemblance to squirrels is misleading and, instead, anomalures are thought to resemble closely the rodent stock from which today's porcupines, rats, and squirrels are descended. Anomalures are an evolutionary enigma, very ancient and yet at the same time highly specialized. The anomalure lineage is thought to have survived for so long because they have specialized in a substance that is easily found but that few other mammals can eat: tree bark. Their family name, means "the strange-tailed ones." All members use the furred membranes for gliding between trees, sometimes very adeptly. This ability is thought to have arisen originally for moving between the widely spaced trees of dry seasonal forests, not unlike today's Brachystegia "miombo" woodlands. A pliable fur-coated membrane extends between the legs and also extends between the hind legs and the tail. The presence of a similar membrane in 14 genera of flying squirrels (Aeretes, Aeromys, Belomys, Biswamoyopterus, Eupetau-rus, Glaucomys, Hylopetes, Iomys, Petaurillus, Petaurista, Petino-mys, Pteromys, Pteromyscus, Trogopterus) and the marsupial genus Petaurus is a remarkable example of convergent evolution.

The systematic position of this family has been much debated. In the past they have variously been grouped with Old World porcupines, the mouse-related rodents, and the squirrel-related rodents. Sometimes, they are included in the separate suborder, Anomaluromorphia, and superfamily, Anomaluroida. This also includes another family, the Zeg-doumyidae, which is extinct. Unlikely as it may seem, the closest relative to the anomalures may well be the springhare (Pedetes capensis), a thoroughly terrestrial resident of southern Africa's semi-arid grasslands. It too has a very ancient lineage.

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