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Re: INTRODUCING Microraptor gui (or Cryptovolans pauli, or Microraptor pauli, or...)

Thomas R. Holtz, Jr. <tholtz@geol.umd.edu> wrote:

Xu et al. consider the elongated leg wing feathers as gliding supports, and have a restoration of _Microraptor_ with
its leg splayed out to the side. I find this very questionable, given that there is no particular evidence that _Microraptor_ to move into this position (which in your typical dinosaur would require popping the femoral head out of the socket).

No, I don't have any good alternative explanation for the elongated leg feathers. Rudder? Aid in prey capture? Display? Genetic link by serial homology with the arm feathers? Nevertheless, given the constraints of the pelvic anatomy, I do not see how the leg feathers could be used as a laterally-oriented flight surface.

Interestingly, both the fore- and hindlimb feathers of _Microraptor gui_ are asymmetrical. As Xu et al. note, this suggests that the feathers were designed to create an aerfoil (airfoil). Using modern gliding/parachuting primates as a model (e.g. _Propithecus_), it may not be necessary for the hindlimbs to be laterally-oriented in order to provide a surface capable of generating lift during aerial leaps.

Also, if these critters were using their aerodynamic abilities to locomote from trees to the ground (e.g. ambush hunting), they would presumably have landed feet-first. This necessitates a more vertical orientation for the hindlimbs during these short descents.

Ten years ago, Alan Feduccia proposed that sifakas (_Propithecus_) may represent an evolutionary analog to an early stage in avian flight. _Microraptor gui_ (?or _Cryptovolans pauli_) may represent a theropod sifaka.

Feduccia, A. (1993). Aerodynamic model for the early evolution of feathers provided by _Propithecus_ (Primates, Lemuridae). Journal of Theoretical Biology.

Hats off to William Beebe!


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