Fig 1.
Formation of the composite wing of Draco dussumieri during the initial phases of the gliding flight.
(A) Seen from below. Image composed of ten still frames from a video clip (S1 Video); consecutive frames are 1/30 s apart from each other. (B) Seen from the front (left, consecutive photos are 181 ms apart from each other) and from below (right; corresponding photos of the same phases). White arrows indicate the position of the hands. For explanation see text.
Fig 2.
Details of the composite wing in Draco dussumieri.
White arrows indicate the position of the hands. (A) During takeoff jump. Note the straight back while the patagium is furled. (B) During glide phase. Note the cambered shape of the patagium and the arching of the back when the patagium is extended. (C- F) During glide phase, seen from the side (C, D) and from below (E, F). Note the strongly adducted hands and the fingers touching the dorsal side of the patagium. The postaxial part of the upper arm is below the leading edge of the patagium. (G, H) Apparent rupture of the patagium (green arrow) posterior to second elongated rib. (I) Two males uncontrolledly descending during agonistic interaction without their forelimbs being in contact with the not fully extended patagium.
Fig 3.
Draco dussumieri (adult male) gliding from one tree to another.
Sequential photographs were taken at 6.5 frames/s. (A) Starting point where the lizard had been perching and displaying. (B) After the initial jump, the patagium is spread and the hands are moved above the patagium. (C) The hands are being placed on the dorsal side of the leading edge of the patagium. (D) After the composite wing is formed, the glide path becomes more horizontal. (E- F) Before landing, the glide direction is adjusted and the patagium is increasingly oriented upward, accompanied by a strong upturn of the glide path. (G) During landing, the forelimbs are extended forward towards the landing spot, and the head is moved up and back.
Fig 4.
Landing of Draco dussumieri at the end of a gliding flight.
Still frames from a video sequence (S4 Animation); consecutive images are 1/60 s apart from each other. (A) The lizard approaches the landing site and its hands are lifted from the surface of the patagium. (B) The hands are free and the arms move forward towards the landing site. (C) Immediately before the impact, the forelimbs are extended forward and the head is moved up and back. The furling of the patagium begins. (D) Arms and chest but not the head hit the landing site. The hands grasp the surface. (E) Legs, abdomen and head hit the landing site. (F-H) The body is erected and the furling of the patagium is completed.
Fig 5.
Draco dussumieri disconnecting the composite wing immediately before landing.
Photographs A and B show the same individual on two different instances, C a second individual, and D-F a third individual at three different instances. (A) Shortly before reaching the landing point, the aerofoil is orientated more vertically. The fingers are still touching the leading edge of the patagium. Note the ulnar deviation of the hands. (B) The hands have just been lifted from the patagial surface and are still strongly adducted. (C) At a remaining distance of only a few centimeters from the landing point, the forelimbs and hindlimbs are extended forward towards the tree. (D-F) Different states during the release of the patagium: (D) the fingers of the left hand have been lifted up and thus have just lost contact with the patagium; the fingers of the right hand still touch the leading edge. (E) the fingers of the left hand have just been lifted from the dorsal surface of the patagium; the right hand has already been rotated forward. (F) the left hand is rotated forward; the right forelimb is already moved forward and not visible from behind anymore.
Fig 6.
Wings and patagia of vertebrate groups employing flapping (A-C) and gliding (D-H) flight. Colours mark the major aerodynamic surfaces (yellow) and the skeletal and muscular structures that control them (red). A: Pterosaur (Rhamphorhynchus, extinct); B: Bird (Columba); C: Bat (Phyllostomus); D: Flying fish (Hirundichthys); E: Flying frog (Rhacophorus); F: Parachuting gecko (Ptychozoon); G: Flying squirrel (Petaurista); H: Flying lizard (Draco). In Draco, the forelimbs are connected to the lift-generating surfaces of the patagium only for the duration of the flight.