The Anomaluridae are a family of rodents found in central Africa. They are known as anomalures or scaly-tailed squirrels or African flying squirrels. The six extant species are classified into two genera: Anomalurus, and the smaller, Idiurus.
All anomalurids have membranes between their front and hind legs like those of the boreal flying squirrels, but they are not closely related to the flying squirrels that form the separate tribe Petauristini of the family Sciuridae. They are distinguished by two rows of pointed, raised scales on the undersides of their tails. Like North American flying squirrels, these species have a cartilaginous rod that aids them in maintaining the extension of the patagium when in flight; unlike flying squirrels, their cartilage originates at the elbow joint rather than at the wrist.
Most anomalurid species roost during the day in hollow trees, with up to several dozen animals per tree. They are primarily herbivorous, and may travel up to from their roosting tree in search of leaves, flowers, or fruit, although they also eat a small amount of insects. They give birth to litters up to three young, which are born already furred and active. The others include the "true" or sciurid flying squirrels of boreal Eurasia and North America, the colugos or "flying lemurs" of Southeast Asia, and marsupial gliding possums of Australia.
Taxonomy
Taxonomy follows .
- Family Anomaluridae
- Genus Anomalurus
- Beecroft's flying squirrel, Anomalurus beecrofti
- Lord Derby's scaly-tailed flying squirrel, Anomalurus derbianus
- Pel's flying squirrel, Anomalurus pelii
- Dwarf scaly-tailed squirrel, Anomalurus pusillus
- Genus Idiurus
- Long-eared flying mouse, Idiurus macrotis
- Pygmy scaly-tailed flying squirrel, Idiurus zenkeri
Fossil genera
Several fossil genera are also known:
- Genus †Argouburus
- Genus †Kabirmys
- Genus †Paranomalurus
- Genus †Pondaungimys
- Genus †Shazurus
Specialized morphology
Patagium
The gliding membrane (patagium) of scaly-tailed squirrels consists of three distinct sections: the anterior propatagium extending from the shoulder along the forelimb, the large middle plagiopatagium spanning from forelimb to hindlimb, and the posterior uropatagium connecting the hindlimb to the proximal portion of the tail.
Anomalurids are unique among all other gliding mammals in having a cartilaginous elbow spur, called the unciform element, which projects laterally from the ulna to support the anterior edge of the membrane during flight. This spur differs from the wrist-based styliform cartilage found in flying squirrels, having evolved from the triceps tendon rather than skeletal elements.
The membrane attachment patterns vary between genera, with Anomalurus species having more extensive connections to the hindlimbs compared to the smaller Idiurus species. A specialized brush of stiff hairs on the membrane's dorsal surface just behind the elbow spur serves an aerodynamic function, passively thickening the wing's leading edge to improve airflow during gliding.
Tail
Unlike the rougher-barked trees found in habitats of other gliding mammals, Anomalurids live on trees with relatively smooth bark like Milicia excelsa that offer fewer natural grip points for claws. This has resulted in them evolving an adaption to aid them in the form a distinctive keratinous scaly organ on the ventral surface of their tail base that gives scaly-tailed squirrels their common name.