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A complete skeleton of the oldest known flying reptile, Coelurosauravus jaekeli, from the Upper Permian of Germany, and reexamination of other specimens demonstrate that this animal had a gliding apparatus unlike that of any other tetrapod. The lateral gliding membrane was supported by radially disposed, greatly elongated bony rods of dermal origin in the thoracolumbar region, rather than by internal skeletal elements such as ribs and limb bones. The rods are independent of the ribcage and arranged in distinct bundles to form a cambered wing.
Extant and fossil terrestrial vertebrates have developed a diversity of gliding mechanisms (1, 2): (i) flattening of the body by drawing in the ventral surface of the body (the flying snake, Chrysopelea); (ii) spreading of webbed feet or membranous flaps along the hind edges of the limbs, in some instances accompanied by flattening of the body (some flying frogs such as Hyla miliaria and Rhacophorus rheinwardtii); (iii) expansion of a lateral skin fold between the fore- and hindlimbs [flying phalangers (Marsupialia), flying lemurs (Dermoptera), and flying squirrels]; (iv) expansion of a lateral membrane supported by elongated, flexible thoracolumbar ribs [as in the gliding lizard Draco (3)]; and (v), as (iv), but with elongated, rigid ribs, which form hinge-joints with the considerably enlarged transverse processes of the dorsal vertebrae [Late Triassic Kuehneosauridae (4, 5)]. Although many birds, especially large forms, are skilled gliders, bats rarely glide, perhaps because they cannot control gliding and vary wing area as much as birds can (2). Here we describe a new skeleton of the oldest known flying tetrapod, CoeLurosauravus (6, 7), and show that it had a different gliding mechanism from those examples mentioned above.
The Late Permian Coelurosauravus is a small diapsid reptile most closely related to the Neodiapsida, the clade including all archosaurian and lepidosaurian reptiles (8). The most diagnostic features of Coelurosauravus are the chameleon-like frill at the back of the skull roof, formed primarily by the squamosals, and the presence of numerous long, rodlike bones that supported a lateral gliding membrane (8, 9). These rods were originally misinterpreted as the fin rays of a coelacanth fish superimposed on a small reptilian skeleton and were, for the most part, removed during preparation of the holotype of Coelurosauravus...