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Re: Changyuraptor, new big microraptorine theropod from Early Cretaceous of China



I was interested to see that the new cladogram disagrees with that of the
recent Foth et al. Archaeopteryx paper in two important respects: It moves
Balaur back to the Velociraptorinae, within Dromaeosauridae, and recovers
the Deinonychosauria as a monophyletic clade.

Jason Brougham
Senior Principal Preparator
American Museum of Natural History
jaseb@amnh.org
(212) 496 3544





On 7/15/14 10:00 PM, "Mike Habib" <biologyinmotion@gmail.com> wrote:

>Thanks to Kevin for the excellent commentary on our manuscript. We
>declined to explicit support either a more arboreal/gliding or
>WAIR/powered model for exactly the reasons Kevin notes - a combination of
>limited forewing preservation (which is why we left out commentary on the
>matter) and polarizing opinions we thought best to stay clear of in this
>case. 
>
> 
>As a quick follow-up to the gliding prospects: I (and at least most of my
>co-authors) agree entirely that a sprawling mode for the hind limbs is
>extremely unlikely (at best) in microraptorines. However, this may not
>speak directly to the validity of a general gliding model (though it does
>speak strongly against the original ³tetrapteryx² glider concept). The
>hind limb feather surfaces have broad, low-aspect planforms that are
>suitable as control surfaces producing both roll and yaw when held below
>the body (through a combination of high drag and high lift - it should be
>noted that lift can be oriented in any direction that is perpendicular to
>flow). These sorts of control options are advantageous in both a gliding
>and a WAIR/descent model, so I remain cautious in suggesting that the
>non-sprawling models necessarily speak to one or the other.
> 
>[It is possible that microraptorines used the forelimbs to support their
>weight during arboreal gliding, with the hind wings providing control
>authority in roll and yaw, and the tail providing control authority in
>pitch (the latter being particularly important for animals with long
>torsos, since the center of mass tends to be somewhat caudally located
>relative to the wings). It is, of course, also quite possible that that
>same control authority was used with behaviors like WAIR and flapping
>descent. The latter does have the advantage of providing an explicit
>model for flight stroke evolution.]
>
> 
>To expand briefly on Kevin¹s excellent point about thrust production: in
>living powered flyers, the wing undergoes twist during the flight stroke
>(both phases). During the downstroke phase, this twist reorients much of
>the lift from the distal wing to produce thrust instead of weight
>support. The trick is that the distal wing can also provide weight
>support at lower degrees of twist (as is the case in soaring flight, for
>example). One thing that might be worth looking at in paravians, in
>addition to the feather structure and location, are the adaptations for
>twisting the distal wing. If ³twistiness² shows up before large wing
>areas (either ontogenetically or evolutionarily) in microraptorines, then
>it would support hypotheses such as flapping-descent and other
>non-gliding first, early flight stroke models. Unfortunately, the new
>Changyuraptor specimen doesn¹t preserve the required distal wing anatomy
>to test this idea, but other specimens may be promising.
> 
>Cheers,
> 
>‹Mike
>
>
>
>
>On Jul 15, 2014, at 3:45 PM, Kevin PADIAN <kpadian@berkeley.edu> wrote:
>
>> I think what Mike says is reasonable, although because so many people
>> (read:  potential reviewers) have such different views on early flight
>> capabilities, it's difficult to say much of anything definitive
>> without alienating your chances for a high-profile publication.
>> 
>> People who think gliding has to precede flight may be comforted by the
>> calculations here, although drag is likely to have been far more
>> effective than lift, especially given that the legs could not
>> apparently be placed in a batlike posture and hence could not have
>> spread the feathers horizontally to form an effective airfoil that
>> transmitted significant lift.  This, of course, depends on the
>> orientation of the feathers with respect to the hindlimb parts, which
>> is not clear from any of these allegedly gliding animals.  However an
>> unusual configuration, such as a lateral splay of the hip joint, has
>> to be demonstrated rather than assumed, and it has not been for any of
>> these animals beginning with the original interpretation of
>> Microraptor.
>> 
>> People who think gliding is not necessary for flight may find the new
>> discovery consistent with the WAIR hypothesis:  once up a tree the
>> animal may have fluttered down with its forelimbs (not glided), using
>> the hindlimbs and tail for drag and lift, plus dynamic stability. The
>> humerus and forearm, compared to the femur and tibia, are no longer
>> proportionally than in Archaeopteryx, a smaller animal.  It is
>> surprising that this new animal shows so little evidence of forewings,
>> about which the authors say almost nothing; if they were large one
>> might have expected them to overlap the body, though they may have
>> been prepared away.  However, the feathers that produce the most
>> thrust, as opposed to lift for gliding, are not mostly on the inner
>> wing but on the hand, which was not preserved here.  Baby birds
>> develop these outer feathers first, and they are the ones that are
>> effective in WAIR at early stages.  -- kp
>> 
>> 
>> Kevin Padian
>> Professor and Curator
>> Department of Integrative Biology and Museum of Paleontology
>> University of California, Berkeley CA 94720
>> 
>> 
>> On Tue, Jul 15, 2014 at 3:27 PM, Mike Habib <biologyinmotion@gmail.com>
>>wrote:
>>> 
>>> We don't exclude other functions in the manuscript. Rather, the focus
>>>is on the performance effects the feathers would have related to aerial
>>>locomotion (sustained or not). These effects occur regardless of the
>>>selective landscape of the feathers. Since some of the performance
>>>outcomes are potentially advantageous (control of pitch, for example)
>>>we felt that referring to these as likely aerodynamic functions was
>>>warranted. Display-related or not, they will still produce fluid
>>>forces. Furthermore, the allometry of the feathers and tail length
>>>relative to body size is consistent with a pitch control hypothesis.
>>>This does not exclude display as an additional (or even primary)
>>>function.
>>> 
>>> Cheers,
>>> 
>>> --Mike H.
>>> 
>>> Sent from my Cybernetic Symbiote
>