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Tetrapteryx

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Bastet sparrow
Passero di Bastet
Tetrapteryx arvensis

A small flying animal common in the prairies and woodlands of Bastet.

«The true diversity of diplopterygians, the masters of horoid skies, is still poorly recorded. They can be found perching on the highest branches of the twilight forests, nesting in the ground of spongegrass prairies or diving for silverdarts in the open ocean. Their most obvious and distinctive feature is a double pair of wings, hence the name: the front pair is usually larger than the back one, so that they're also called "greater wings" and "lesser wings"; both are composed by a thin limb expanded by compact rays. By superimposing, these rays can change the overall shape of the wing. Their paralimbs not only are very developed, but they work as true legs, having developed two "toes", and being used to walk and perch.
This peculiar arrangement of limbs forces the diplopterygians to walk slanted forward; the post-pneumatic abdomen, long and thin like a tail during flight for balance and steering, is retracted in a short, blunt appendage in order to be closer to the creature's centre of mass. Because of the large lung and air sacs, though, this posterior half, albeit larger than the head and chest, is not significantly heavier. All the body is covered in fine hair or down, becoming a thick fur in the large tundra-dwelling species of Sekhmet.
As in Earth's insects, the presence of four wings allowed for an array of adaptations, developing for example the greater wings into protective shells, or the lesser ones into halteres for balance. While their structure does not allow to change shape as easily as birds or bats, wing surface can be modified by combining or selectively folding them: for example, in a Bastet sparrow preparing to land the lesser wings will unfold and combine with the greater ones in order to act as a parachute. Large oceanic soarers, a common sight during our voyage on the Greyhound, have long and narrow greater wings, while smaller aerial hunters have delta-shaped wings to swoop on their preys at high speed.
Some speculate that diplopterygians emerged from a lineage of aquatic urogamians; this would explain both the fin-like wings (developed in turn from the four true limbs of early urogamians) and the light bones, which would've been used for buoyancy at first and for flight later.»
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