RE: Senter 2006, Confuciusornis, and humeral mobility

["Jason Brougham" <jaseb@amnh.org>]

Jaime,

Another contrary example to using relative length as the main metric of
reduction in skeletal elements occured to me.

The humerus of a hummingbird is also shorter, relative to the manus, or
relative to the humeral width, or relative to the culmen to vent length,
than the ancestral condition, but can we say it is reduced? Instead it
seems to me it is specialized, sporting exaggerated processes, and even
more high - performance than the ancestral condition.

-Jason


>
>
> Jason, I think you misunderstood my notation:
>
>   I compared two specimens of *Archaeopteryx,* the München and Berlin
> specimens: In both, the second digit, or mdII, is 48% and 57% longer
> than the third digit, or mdIII. In *Confuciusornis sanctus*, this
> proportion is only 2% (md3/md2). I did not calculate the metacarpal in
> this. I also looked at a few other birds, but for reasons including loss
> of the third and fourth phalanges of digit three in various forms, this
> value was less useful.
>
>   If I were to use digit length, not excluding the ungual, then this value
> changes: In Archaeopteryx* (specimens above, and respectively), the
> proportion of digit II (md2)/MCII is 64% and 82%; in *Confuciusornis
> sanctus* (using GMV 2131 and GMV 2132, again, repsectively), the
> proportions are 161% and 181%. These measurements _do_ fall into the
> values you argue, but as noted they include the unguals.
>
>   If I were to test the individual proportions of the phalanges
> (mdII-2/mdII-1), what might we get? For *Archaeopteryx* (same specimens)
> we get: 48% and 25%, respectively. For *Confuciusornis sanctus* (GMV
> 2132), we get 30%. This shows a median measurement.
>
>   This argues that the phalanges are not, as you argued, hypertrophied.
> They are short or fall in the range of another, earlier bird without a
> more specialized brachial-pectoral apparatus.
>
> You wrote:
>
>   "I made no comparisons to Archaeopteryx. [...] But the expansion of the
> diameter of Ph 1 II is a feature seen in both Microraptor and
> Confuciusornis and it is therefore interesting to me."
>
>   Why are you excluding *Archaeopteryx* from this at all? Presumably, it
> lies closer to *Confuciusornis sanctus* than does *Microraptor [I assume
> you are using] zhaoianus* -- I know Paul disagrees, and maybe you place
> emphasis on *Microraptor* for this reason, but you shouldn't; if the
> conditions are convergent, they are less useful for your work than you
> may think. For reference, I used Hwang et al., 2002:
>
>   CAGS 20-7-004: mdII-2/mdII-1: 24% ; md3/md2: 12% ; md2/MCII: 27%
>
>   In my original measurements, it should be noted, *Confuciusornis
> sanctus* lacks an elongation of mdII-2 relative to mdII-1. It is, in
> short, short. Otherwise, the proportions of the digits or the phalanges
> (on a purely linear level) are similar across most of these taxa. They
> supported feathers, so presumably there was a constraint involved
> (number of feather attachments would be my guess), and these birds (and
> nonavian paravian) are all close to one another in size.
>
>   But let's care for a second that only the diameter of the crest on
> mdII-1 is relevant, and no other measurements aside from the length.
> While Paul (2002) argues that the crest is present in *Archaeopteryx* (I
> am unclear which specimen; pg.106-407, Paul references Zhou & Martin,
> 1999, which I do not have), and in *Sinornithosaurus millenii*
> (holotype, his "adult specimen," into which he puts all *Microraptor*
> species and specimens), larger in the latter than the former. Using
> Paul's figure, length/diameter (at its greatest points; a fault, I know)
> in *Sinornithosaurus millenii,* *Archaeopteryx* whatever, and
> *Confuciusornis sanctus* are: 3.71, 5.7, and 3.
>
>   Using this measurement, then yes, I would say the phalanx is broader
> relative to the condition of, say, *Archaeopteryx* or *Microraptor.* But
> to simply say the phalanx is incrassate and subject this then to calling
> the digit hypertrophic is grossly incorrect, as it infers both a length
> value (which is not apparent) and other proportional values, none of
> which were mentioned. I explain above that only in the diameter of
> mdII-1 does the manus of *Confuciusornis sanctus* even barely exceed the
> conditions of other taxa. I could go further: I could demonstrate using
> other baselines (such as MCI length, or md1-1 length) the shortness of
> the elements here in contrast to other taxa.
>
>   I do not think using diameter alone is a valid test of your argument.
>
> Cheers,
>
> Jaime A. Headden
> The Bite Stuff (site v2)
> http://qilong.wordpress.com/
>
> "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
>
> "Ever since man first left his cave and met a stranger with a
> different language and a new way of looking at things, the human race
> has had a dream: to kill him, so we don't have to learn his language or
> his new way of looking at things." --- Zapp Brannigan (Beast With a
> Billion Backs)
>
>
>
>
>
> ----------------------------------------
>> Date: Mon, 28 Mar 2011 08:57:26 -0400
>> Subject: RE: Senter 2006, Confuciusornis, and humeral mobility
>> From: jaseb@amnh.org
>> To: qi_leong@hotmail.com
>> CC: jaseb@amnh.org; dinosaur@usc.edu
>>
>> Hi Jaime,
>>
>> By hypertrophied I mean that all the elements of the second digit, with
>> the exception of the ungual, are larger and more robust than either of
>> the others, not reduced relative to them. The diameter of PH 1 II must
>> be
>> three times that of PH 1 III. Though the metacarpal may be only 2%
>> longer
>> that Mc III, it is longer nonetheless, not reduced.
>>
>> I made no comparisons to Archaeopteryx. That must surely be the point of
>> our misunderstanding. You are comparing all elements to Archaeopteryx,
>> and
>> describing any differences as reductions or enlargements from the
>> condition in Arcaheopteryx, while I am not.
>>
>> But the expansion of the diameter of Ph 1 II is a feature seen in both
>> Microraptor and Confuciusornis and it is therefore interesting to me.
>>
>> -Jason
>>
>>
>>
>>
>> >
>> > Jason, I think there are a few problems with your hypthesis (I meant
>> to
>> > get back at this earlier).
>> >
>> > The first issue is that nearly all *Confuciusornis sanctus* specimens
>> > are preserved with their manus in either ventral or dorsal view,
>> depending
>> > on what orientation the wing lays. And they are all, to varying
>> degrees,
>> > crushed, distorting the relative placement of features.
>> >
>> > The second issue is your use of "hypertrophied" in reference to mdII.
>> > I'm not sure what you mean by this, but there are two possibilities:
>> one
>> > is length, in that mdII is somehow proportionately longer than another
>> > digit than in other taxa, and the other is that the digit is
>> > morphologically incrassate, expanding its apparent features in other
>> > dimensions than length.
>> >
>> > I think I can rule out "hypertrophied" length, as mdII is only 2%
>> longer
>> > than mdIII in the specimen being referenced (Chiappe et al., 1999,
>> fig.
>> > 39). Compare this to *Archaeopteryx*: München specimen, BSP 1999 I 50:
>> > 48%, and Berlin specimen, HMN 1880 (counterslab 1881): 57%.
>> >
>> > A few things make me think incrassate proportions (diameter or
>> > circumference versus length) are not at fault. This includes, but is
>> not
>> > limited to, the peculiar articulation of mdII-2 and mdII-3 (the
>> ungual):
>> > The distal end of mdII-2 has no apparent ligament pits, nor does it
>> appear
>> > to have paired condyles. The proximal end of the ungual is not concave
>> in
>> > profile, either ascribing a relatively straight articulation (and thus
>> > less flexibility at the joint, if any), or that the condyle of mdII-2
>> sat
>> > within a bowl-like cotylus on the ungual, which I favor here. The
>> proximal
>> > end of the ungual is smaller dorsoventrally than in either of the
>> other
>> > unguals, and this simply supports smaller size of distal mdII-2
>> relative
>> > to other penultimate phalanges, in keeping with the lack of
>> incrassitude
>> > of mdII-2.
>> >
>> > While I cannot contradict the observation of large condyles on mdII-1,
>> I
>> > would like to note that one of them is larger than the other, but I
>> think
>> > this is likely evidence of distortion rather than a trochlea; the
>> presence
>> > of a broad lateral blade on mtII-1, which expands from the distal end
>> of
>> > the phalanx and incorporates the lateral margin of condyle, suggesting
>> the
>> > condyle lacks a ligament pit (at least on one side).
>> >
>> > But this is all in comparison to the specified specimen. I am not
>> > familiar with better specimens, especially published figures, and
>> would
>> > like to have a better sample. What this specimen says, however, is not
>> > supportive of a very flexible second digit, at least to the same
>> degree as
>> > *Archaeopteryx lithographica*.
>> >
>> > Cheers,
>> >
>> > Jaime A. Headden
>> > The Bite Stuff (site v2)
>> > http://qilong.wordpress.com/
>> >
>> > "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>> >
>> >
>> > "Ever since man first left his cave and met a stranger with a
>> > different language and a new way of looking at things, the human race
>> > has had a dream: to kill him, so we don't have to learn his language
>> or
>> > his new way of looking at things." --- Zapp Brannigan (Beast With a
>> > Billion Backs)
>> >
>> >
>> >
>> >
>> >
>> > ----------------------------------------
>> >> Date: Sun, 27 Mar 2011 21:03:37 -0400
>> >> From: jaseb@amnh.org
>> >> To: tijawi@gmail.com
>> >> CC: dinosaur@usc.edu
>> >> Subject: Re: Senter 2006, Confuciusornis, and humeral mobility
>> >>
>> >>
>> >> > Jaime Headden wrote:
>> >>
>> >> >> *Confuciusornis sanctus* has ... reduced form of the
>> >> >> second, major digit
>> >>
>> >> The second digit is hypertrophied, not reduced. Only the ungual is
>> >> smaller. The diameters of metacarpal II and Phalanx 1 II are much
>> >> greater
>> >> than those of digit III. The trochleae are large and well developed
>> (Fig
>> >> 39 Chiappe et al. 1999. Specimen GMV-2132).
>> >>
>> >> I agree that the deltopectoral crest may have functioned in tree
>> >> climbing
>> >> with the hands but, of course, this is not mutually exclusive with
>> >> flight
>> >> stroke functions. My hypothesis is that the huge deltopectoral crest
>> >> could
>> >> have functioned to give the deep pectoralis muscles greater leverage
>> in
>> >> rotating the humeral trochlea dorsally for a powered flight stroke.
>> >>
>> >> Jason Brougham
>> >> Senior Principal Preparator
>> >> Department of Exhibition
>> >> American Museum of Natural History
>> >> 81st Street at Central Park West
>> >> 212 496 3544
>> >> jaseb@amnh.org
>> >>
>> >
>>
>>
>> Jason Brougham
>> Senior Principal Preparator
>> Department of Exhibition
>> American Museum of Natural History
>> 81st Street at Central Park West
>> 212 496 3544
>> jaseb@amnh.org
>>
>


Jason Brougham
Senior Principal Preparator
Department of Exhibition
American Museum of Natural History
81st Street at Central Park West
212 496 3544
jaseb@amnh.org