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Re: Science feather strength debate



I read the relevant letters and e-mails again and I will attempt a  summary of 
the conclusions here.

1. Nudds and Dyke, in their Response To Mr. Paul's letter and the letter of 
Zheng et al., admit that the Zheng et al. specimens of Confuciusornis could 
flap, assuming that all the measurements provided by Zheng et al. are correct.

2. Nudds and Dyke found that, using Mr. Paul's lower mass estimate, 
Archaeopteryx has a safety factor lower than any modern bird, but probably 
enough for some level of flapping.

3. Nudds and Dyke  do not seem to have a reply for the observation that no 
proximal rachises are known for Archaeopteryx.

It appears then that we are all now basically in agreement. Nudds and Dyke have 
revised their assessments of the flight capabilities of Confuciusornis (with 
the possible exception of some specimens or even a flightless cohort within the 
genus) and Archaeopteryx upwards. They did this in response to the suggestions 
of Mr. Paul and of Zheng et al.

Thank You, Mr. Paul, for your contributions. I apologize for those times that I 
have been discourteous in corresponding with you. I feel that this debate has 
been fruitful but I regret that it was so adamant at times.

Now I would like to see them apply their method to Microraptor and Anchiornis!

-Jason

On Nov 11, 2010, at 9:42 PM, GSP1954@aol.com wrote:

> Oh this is just unbelievable. 
> 
> In a message dated 11/4/10 9:54:54 AM, jaseb@amnh.org writes:
> 
> << >>> a 20% difference in mass makes a big difference in aerodynamics and 
>>> This is ridiculous. The mass of an individual bird can vary by 20% or 
> more 
>>> over a matter of hours (if it gorges) or days (as body fat deposits 
> vary). 
>>> It is common for very long distance migrating birds to start out heavy 
> with 
>>> fat and lose it by the end of the journey. The bird can effectively fly 
> at 
>>> the beginning and end of the mission. In any case, as I have stressed 
>>> repeatedly in the literature, it is not possible to restore the mass of 
> an 
>>> individual specimen better than +/- 20% or more because of problems with 
> restored 
>>> volume, SG, and normal changes in an individuals mass. The problem with 
> the 
>>> Nudds and Dyke was that they overestimated the mass of the Archaeopteryx 
>>> specimen they examined by a factor of about two, Confusicusornis by 
> about three. 
>> 
>> If 20% doesn't matter then I wonder why you bothered adjusting Yalden's 
> estimate for the body mass of HMN 1880 by 13% (from 271 to 234g). You also 
> spend some time discussing the relative merits of a pectoralis mass between 5 
> and 15% of body mass.> 
> 
> Jason is being flippantly unscientific. I did not "adjust" the Yalden 
> estimate. When I complete a skeletal restoration I normally do a mass 
> estimate 
> and the 234 g value is what I happened to came up with for 1880, so I 
> published the result. It's the usual technical process.  That the results of 
> moi, 
> Yalden and Elzanowski are not identical is to be expected especially since it 
> is not possible to restore body mass closer than ~20%. That they are so 
> similar strongly favors their being close to correct. I spend time discussing 
> the possible pectoralis mass range because that 3 fold difference for the 
> specific portion of total mass that actually powers the wings most certainly 
> does have tremendous importance, duh.  
> 
>> Moreover, we would both agree that 20% doesn't matter to extant migratory 
> birds with highly derived flight apparatus, but modern birds have a lot of 
> spare capacity. They can stoop at 200 mph, hover in mid air, and fly 
> thousands of miles! In an animal that is barely capable of aerodynamic 
> locomotion, 
> like any hypothetical ancestor of birds, 20% could be a crucial difference 
> between ascending flight and gliding.>
> 
> Since the mass of an individual animal can easily vary this much this claim 
> too is flippant. And to repeat, N&D were off by factors of 2-3, not 
> 0.2-0.3.  
> 
>> I agree that Nudds and Dyke used mass estimates that are too high and 
> rachis measurements that were too small, and that their conclusions must thus 
> be reconsidered. But Zheng et al. found that Nudds and Dyke still 
> demonstrated that both birds had weak rachises compared to extant birds of 
> the same 
> mass. I still think they flew, but this contribution by Nudds and Dyke 
> suggests 
> that Confuciusornis probably couldn't pull the miraculous maneuvers 
> (pouncing on fish and then taking off from the water surface) that 
> kingfishers do 
> today. >>
> 
> How often do I have to repeat this? Can't some of you read? It is 
> absolutely impossible to currently restore or compare the feather strength 
> and 
> therefore flight performance of any Archaeopteryx specimen because in none 
> are the 
> feather base shafts whose diameter must be measured preserved!!! Give it 
> up, the data is simply not available. For the N&D method to be applied to the 
> urvogel will require the discovery of a new specimen with the primary 
> feather bases preserved. Let us hope even as we do not hold our breathes 
> (Zheng et 
> al say that only 4 of their 536 Confuciusornis specimens have good feather 
> bases). 
> 
> And Zheng et al. did not reanalyze Archaeopteryx. 
> 
> As for the Zheng et al. reestimate for Confuciusornis feather strength they 
> are - obviously -- way too pessimistic because they -- hello -- assumed 
> that the N&D 3 times too high mass estimate of half a kilogram is correct. I 
> did not try to come up with a new feather strength estimate in my reply 
> because I did not have any Confuciusornis specimens to check out the N&D 
> shaft 
> diameter measurement which I -- correctly as Z et al proved -- did not trust. 
> And I am suspicious about the N&D method in any case because it may not take 
> feather overlap co-bracing into sufficient account. I will not do the 
> calculations using my correct mass and Z et al's correct shaft diameters 
> because I 
> have no plans to further work on the issue at this time there being lots of 
> other things on my plate, and others will certainly do it and what's wrong 
> with that. 
> 
> GSPaul </HTML>

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