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

[Ruben Safir <ruben@mrbrklyn.com>]

On 03/14/2018 11:18 PM, Tim Williams wrote:
> I don't see why _Archaeopteryx_ couldn't have flown up into a tree.


Tim - that was your observation that the bird couldn't leap and beat its
wings for flight and should be aborial.  I read that article and a
couple of others and agree that they seem to agree that without the
modern flight stroke, it would be very hard for them to get lift from a
stationary position.  That would make them generally ground based,
getting lift from running, although you said that would be evidence that
they lived in the canopy.

You wrote:

This is an idea borrowed from Mayr 2017 (DOI
10.1007/s10336-017-1451-x), which is cited here.  I disagree.  There's
no evidence that the supracoracoideus pulley, keeled sternum,
dorsolateral glenoid fossa, or alula were necessary for a vertical
take-off.  Vertical take-offs are initiated by the hindlimbs in extant
birds (Earls 2000 JEB 203: 725-739), and it's likely that
_Archaeopteryx_ was capable of the same (leaping into the air, with no
need for a running take-off; Dececchi et al. 2016 DOI
10.7717/peerj.2159). The wings are deployed for the climb-out phase of
the launch, and a modern avian flight stroke is not essential for this
- just large wings capable of thrust generation.

Vertical takeoff is made possible from that modern wing stroke (and I
don't see the anotomy for the verticle leap either).  The two things
more likely co-evolved as a single movement, the leap and then the
upward stroke.  Look how swans do it.  They barely rotate that wing and
gain upward lift through wing aerodynamics and horizontal speed.
Archaeopteryx doing the same makes total sense and that would explain
why the flight feathers developed first, before the modern wing beat.
It would also support the use of that long tail to help with stabilized
flight at low speed. It would need the aerodynamic lift of the flight
feathers as opposed the the power drive of a modern bird.