| Pterosaurs took to the air about 225 million years ago, preceding birds
and bats by over 70 million years and being the first vertebrates to fly. The pterosaur skeleton was light and delicate, in
accordance with airborne performance, and as a result few examples seem to have been
preserved as fossils. There is still active debate about the arrangement of the wing and
the mode of flight of pterosaurs, but undoubtedly they were proficient
fliers and as a group existed for about 140 million years.
Pterosaurs are thought to be derived from a bipedal
running archosaur in the late Triassic period, but the fossil evidence is
currently very limited. The outer panel of the pterosaur wing was
supported by a very long fourth digit. They had a keeled sternum for the
medial attachment of the pectoral (flight) muscles, and a short and stout
humerus. Pterosaurs had a bone not seen in other groups - the pteroid
bone. This formed part of the wrist and was elongated in the direction of
the shoulder, supporting part of the wing membrane. Pterosaurs evolved
into a variety of species with sizes from that of a small bird to a
wingspan of eleven or twelve metres.
Quetzalcoatlus
species and Quetzalcoatlus northropi
I am grateful for the following information from James Cunningham
(personal communication):
"Quetzalcoatlus species (span ~15.7 feet) and Quetzalcoatlus
northropi (span ~36 feet) are late-Cretaceous pterosaurs. ... These animals were
capable of active, flapping flight, accelerating from launch to cruise in approximately
15-20 wing strokes. The two animals both had a very high aspect ratio and did not connect
the flight membrane (patagium) to the leg (which carried its own uropatagium and together
with the tiny biological tail, formed an aerodynamic tail structure). When soaring, they
both had an L/D max on the rough order of 28:1 (about equal to the Carbon Dragon and the
WinDancer, and in the case of Qn a similar gross weight), and actively modified their wing
planform in a manner somewhat similar to birds, but controlled sail camber, chord, and
planform in the outer wing membrane with fine structures called
aktinofibrils which were
generally oriented more diagonally than sail battens. The aktinofibrils worked in diagonal
tension, maintaining a camber somewhat similar to Selig's S1223, but with a thinner
airfoil section (outboard, that is -- inboard at the elbow (which for Qn measured 10.5
inches from top to bottom, T/C max was about 32% and the aktinofibril orientation was more
amorphous).
Throughout the wing, zero lift occurred at about -8 to -10.5 degrees,
with a quarter chord pitching moment about -0.3. At higher speeds, by appropriately
positioning the wrist and wing-finger pivot (the joint between metacarpal IV and
phaIanx
V-1), they could reduce span while selectively maintaining the outer wing chords at each
joint or increasing them (for example, during landing approach when they could increase
the wing area while decreasing the span thereby increasing induced drag to aid in
deceleration). They also used a permanent semi-vertical bend near the distal end of
metacarpal IV and a tee-bar shape in phaIanges V 2&3 as a primary dynamic control for
span-wise tension in the wing (unlike many modern sail membranes they had no trailing edge
tendon)."
(The term aktinopatagium was introduced at a conference in 1984
by Schaller for the proposed radial arrangement of strengthening fibres within the wing
membrane. See: Schaller, D. (1985) Proceedings of the international Archaeopteryx
Conference in Eichstatt 1984, 333-348.) |
pterosaur flight