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

["Tim Williams" <twilliams_alpha@hotmail.com>]

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!



Tim







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