A couple of folks have already noted this, but I say one can’t have too much news when it comes to unusual reptiles. A new paper released online by the Journal of Evolutionary Biology re-examines the gliding morphology of Sharovipteryx mirabilis, “Sharov’s Wondrous Wing.”
Sharovipteryx was discovered by paleontologist Alexander Sharov, who found it and another amazing reptile in 1965 while collecting Triassic insect fossils in Kyrgyzstan. The only known specimen of Sharovipteryx shows that it was a slender, lizard-like animal with short arms and very long legs. It is the oldest animal known to have a gliding membrane attached to its limbs, a trait that would later evolve in supreme vertebrate aerialists like pterosaurs and bats. But while pterosaurs and bats expanded their arms and fingers to support their wings, Sharovipteryx is the only known animal to have evolved hindlimb-based wings.
But figuring out what these leg-based wings actually looked like has been a bit tricky. The only known specimen of Sharovipteryx bears an unfortunate resemblance to a crumpled umbrella, so the animal’s appearance in life has been the subject of several different interpretations.
Sharov initially restored the membrane something like a long-legged flying squirrel, stretching from the back of the arms to the front of the legs, with a large membrane running from the creature’s ankles to the base of its tail. Restorations based on Sharov’s work can be seen here and here.
In 1987, Carl Gans, Ilja Darevski, and Leonid Tatarinov reexamined the fossil and concluded that there was no sign of a membrane that connected the front and hind legs. They reconstructed Sharovipteryx with a large membrane across the back of its hind legs and tail, and suggested that a smaller membrane around its sides and/or forelimbs might have been present. Experiments with paper models showed that such a membrane close to the front of the animal would have acted as a canard, stabilizing the animal in the air and extending its glide. Several years ago I made this little drawing based on the interpretation of Gans et al. (although I inadvertently extended the membrane a little further down the tail than it should have been):
Now a new generation of researchers has taken a new look at Sharovipteryx, and have come to a slightly different conclusion. If you look at the little animal in the air in the image above, you can see that its thighs are held in what looks to be a very uncomfortable position, and the gliding membrane generates most of the lift well behind the animal’s center of gravity.
Gareth J. Dyke, R. L. Nudds, and J. M. V. Rayner believe that the fossil shows a membrane in front of the legs, and suggest it stretches from the knee to the armpit, creating a triangular “delta-wing.” Unlike previous reconstructions, theirs distributes the lift across the animal’s center of gravity, and provides a control mechanism: by bending its legs at the knees, Sharovipteryx could have changed the shape of its wing and guided its glide.
The authors also suggest that it might have possessed a small forewing or canard stretching from its neck to the front of its forelimbs (this area is poorly preserved on the fossil). As in earlier interpretations, this would have helped balance the animal and keep its front end from pitching downward in flight.
As is the case with this sort of thing, we won’t know the definitive answer until we find more fossils. But whether or not that happens, Sharovipteryx is sure to attract attention as an early experiment in vertebrate flight.
Dyke, G. J., Nudds, R. L. & Rayner, J. M. V. (2006) Flight of Sharovipteryx mirabilis: the world’s first delta-winged glider. Journal of Evolutionary Biology 0 (0), -. doi: 10.1111/ j.1420-9101.2006.01105.x
4/10 Followup: Rigor Vitae has an excellent post discussing the ecology of gliding, modern reptiles and amphibians that have taken up the habit, and three gorgeous paintings of today’s cold-blooded aerialists to boot!
—Matt Celeskey.
File under: Reptiles, Triassic.
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