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Longrich on Archaeopteryx

New in _Paleobiology_

Longrich, N. 2006. Structure and function of hindlimb feathers in Archaeopteryx
lithographica. _Paleobiology_ 32(3):417?431


  "This study examines the morphology and function of hindlimb plumage in
   *Archaeopteryx lithographica*. Feathers cover the legs of the Berlin
   specimen, extending from the cranial surface of the tibia and the caudal
   margins of both tibia and femur. These feathers exhibit features of flight
   feathers rather than contour feathers, including vane asymmetry, curved
   shafts, and a self-stabilizing overlap pattern. Many of these features
   facilitate lift generation in the wings and tail of birds, suggesting that
   the hindlimbs acted as airfoils. A new reconstruction of *Archaeopteryx* is
   presented, in which the hindlimbs form approximately 12% of total airfoil
   area. Depending upon their orientation, the hindlimbs could have reduced
   stall speed by up to 6% and turning radius by up to 12%. Presence of the
   ?four-winged? planform in both *Archaeopteryx* and basal Dromaeosauridae
   indicates that their common ancestor used fore- and hindlimbs to generate
   lift. This finding suggests that arboreal parachuting and gliding preceded
   the evolution of avian flight."

  Preparation early in the study of Archie's Berlin specimen obscured traces of
leg feathers (they are still visible now, but less extensively), which appear
to indicate that the tibia and thigh were encased in pennaceous, flight-like
feathers. Longrich also places the feathers as found into a vane on both the
leading edge of the leg (pretibial) and trailing edge (posttibial) which affect
the reconstruction offered. This reconstruction is very similar to Xu et al's
latest *Microraptor* reconstruction, which puts the legs swumg backward and
somewhat downward from the original, splayed "biplane" model.


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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