The scaly glider has a set of paddle-like scales, growing horizontally from each side of the body and spreading out to form gliding wings. Muscles in the flanks and attached to the ribs give the scales some limited mobility, allowing the bright undersides to be exposed or hidden at will. With a total length of only 30 centimeters (12 inches), including the whip-like tail, and a 'wingspan' of 25 centimeters (10 inches), the scaly glider is one of the smallest and most lightweight of all the dinosaurs.
The Scaly Glider, Pennasaurus volans, is a small, partly quadrupedal, arboreal maniraptoran, closely related to arbrosaurs, from South American tropical rainforests, in The New Dinosaurs: An Alternative Evolution.
Bright flashes of color appear in the heights, up among the branches, creepers and trunks of the Amazon Rainforest canopy. To and fro, the colors dart, like large butterflies, swooping and wheeling in the breezes, then flopping onto a branch and blending instantly with the mottled bark in the dappled sunshine. These are not butterflies, however, but some of the smallest non-avian dinosaurs that have ever existed. Descended from the same coelurosaur stock as the arbrosaurs, the scaly gliders adapted to a gliding life with the evolution of the flowering plants and hence, the butterflies. The latter represent the gliders' principal food. A controlled dive and glide through the air can bring a scaly glider close to a butterfly at rest on a flower, and, with a quick snatch of pointed jaws, the insect is caught and the glider sails on to rest and digest.
Flying and gliding animals frequently evolve in tropical forests. With the network of massive boughs and close-growing branches, animals can easily jump from one tree to another. The more aerodynamic the animal's shape, the further it can jump. The conditions are perfect for the evolution of gliding structures that can carry an animal over even longer spaces. In the case of the scaly glider, these structures consist of broad scales projecting sideways from the body. In flight, they turn the animal into an aerodynamic skimmer, while at rest, they help to camouflage it against the tree-bark. They are brightly hued beneath, but drab when seen from above.