How lizards fly: A novel type of wing in animals

Abstract

Flying lizards of the genus Draco are renowned for their gliding ability, using an aerofoil formed by winglike patagial membranes and supported by elongated thoracic ribs. It remains unknown, however, how these lizards manoeuvre during flight. Here, I present the results of a study on the aerial behaviour of Dussumier's Flying Lizard (Draco dussumieri) and show that Draco attaches the forelimbs to the leading edge of the patagium while airborne, forming a hitherto unknown type of composite wing. The attachment of the forelimbs to the patagium suggests that that aerofoil is controlled through movements of the forelimbs. One major advantage for the lizards is that the forelimbs retain their complete range of movement and functionality for climbing and running when not used as a part of the wing. These findings not only shed a new light on the flight of Draco but also have implications for the interpretation of gliding performance in fossil species.

The postcranial skeleton of the gliding reptileCoelurosauravus elivensisPiveteau, 1926 (Diapsida, Weigeltisauridae) from the late Permian of Madagascar

“…This is permitted by the long arms of this squamate and by a postaxial abduction of the manus. As indicated by Dehling (2017), such an abduction appears possible in weigeltisaurids as well, as shown by the position of the right manus of the Ellrich specimen (Pritchard et al, 2021). Furthermore, as exemplified by Coelurosauravus (Fig.…”

“…In Draco , the patagia are first extended by the contraction of the iliocostal and intercostal musculature (Colbert, 1967; John, 1970; Russell and Dijkstra, 2001) and can be further expanded by interlocking the claws in the scales on the anterior dorsal surface of the patagia (Dehling, 2017). This is permitted by the long arms of this squamate and by a postaxial abduction of the manus.…”

“…The hindlimbs are involved during gliding in most extant gliding reptiles. They are often abducted, positioned at or slightly below the coronal plane of the animal, and bent at the knees so that the forelegs are oriented posteromedially (Emerson and Koehl, 1990; McGuire, 2003; Dehling, 2017). This posture has been proposed to increase stability (Emerson and Koehl, 1990).…”

Influence of posture during gliding flight in the flying lizard Draco volans

“…These gracile squamates show a suite of extreme anatomical specializations to gliding locomotion, including a broad patagium spanning the entire length of the body as well as a pair of hyoid folds that serve as canards to increase stability in flight [9][10][11]. The patagium of Draco is supported by five to seven ribs depending on the species [12,13], which can be extended laterally through muscular contraction and active manual handling to increase the area of the lift-generating surface [9,10,14,15].…”

How lizards fly: A novel type of wing in animals

“…It is commonly assumed that flying lizards use the unfurled patagium to glide and hold the forelimbs free in front of the body while airborne. This assumption was promulgated about 300 years ago, when the first preserved specimens were brought to Europe and reports of flying lizards were accompanied by drawings showing artistic interpretations of them holding their forelimbs in front of the body while "gliding" [9][10][11][12]. The patagium-associated musculature has been suspected to be used to control the direction of the glide path [1,3,[6][7][8], but it has remained unclear how the lizards are able to manoeuvre in the air [2,6].…”