Re: Longrich on Archaeopteryx

[Steven Francis-Coombs <steven.franciscoombs@gmail.com>]

Taken from http://www.albertapaleo.org/

Archaeopteryx and the evolution of avian flight.

Speaker:  Nicholas Longrich, University of Calgary.
7:30-9:30 PM
Friday, September 15th, 2006
Mount Royal College, Room B108

Abstract:
This study examined the morphology and function of hind limb 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 hind limbs acted as airfoils. A new
reconstruction of Archaeopteryx is presented, in which the hind limbs
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.

Information:
This event is jointly presented by the Alberta Palaeontological
Society, Mount Royal College and the CSPG Paleontology Division. For
details or to present a talk in the future please contact CSPG Paleo
Division Chair  Philip Benham at 403-691-3343 or
programs@albertapaleo.org . Visit the APS website for confirmation of
event times and upcoming speakers: http://www.albertapaleo.org/



On 9/6/06, Jaime A. Headden <qilongia@yahoo.com> wrote:
> New in _Paleobiology_
>
> Longrich, N. 2006. Structure and function of hindlimb feathers in Archaeopteryx
> lithographica. _Paleobiology_ 32(3):417–431
>
> Abstract:
>
>   "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.
>
>   Cheers,
>
> Jaime A. Headden
> http://bitestuff.blogspot.com/
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
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