Re: [dinosaur] Archaeopteryx had active flapping flight ability based on wing bone geometry (free pdf)

[Tim Williams <tijawi@gmail.com>]

Ruben Safir <ruben@mrbrklyn.com> wrote:

> Without the lift from the wing stroke the bird just lands on its face
> and the separation of these two aspects of launch that you make here is
> illogical.

To clarify: I was not arguing that a flight stroke per se was not
essential for a launch.  I was arguing that a *modern avian* flight
stroke was not essential.  A more rudimentary flight stroke might have
been sufficient for _Archaeopteryx_ to get itself into the air.


> Furthermore, despite what Earls says, I recommend you walk
> out to Sheepshead Bay in Brooklyn and watch how Swans and Ducks actually
> get into the air.  Swans are not leaping into the air and then taking
> off on winged power.  They 100% depend on building air speed with a
> combination of flight stroke and running on the water.

Not true.  Mike has dealt with this point quite eloquently, so I won't
say anything further.


> Without a
> sternum to anchor chest muscles, that is going to be more true, not
> less.  Flight stroke IS 100% essential.


Yes, a flight stroke of some sort is 100% essential.  But not
necessarily the sophisticated flight stroke of modern advanced flying
birds.  [Note that Rauhut et al. (2018 DOI 10.7717/peerj.4191)
interpret _Archaeopteryx_ as having a large cartilaginous sternum, not
preserved in any specimen. ]



David Marjanovic <david.marjanovic@gmx.at> wrote:

> Or, I suppose, it could just tilt itself, so that its forestroke becomes an 
> upstroke. The tail base is flexible enough to prevent the tail from touching 
> the ground.


Yes, I've wondered that too: Did _Archaeopteryx_ change its posture
during a ground-to-air launch?

According to the osteological interpretation of Agnolin & Novas (2012
DOI 10.1007/978-94-007-5637-3), the humerus in paravian taxa like
_Archaeopteryx_, _Microraptor_, _Rahonavis_, and _Unenlagia_ was able
to be elevated close to the vertical plane, despite the lateral
orientation of the glenoid.  So according to this interpretation, the
flight stroke of _Archaeopteryx_ etc was not as constrained as widely
believed.