RE: On the Issue of Sprawling Dromaeosaurs

["Jaime A. Headden" <qilongia@yahoo.com>]

Kris Kripchak (MariusRomanus@aol.com) wrote:

<Despite the expected attempts to sidetrack and manipulate the argument
(be them intentional or not) in the exact same ways I explicitly stated to
have occurred every other time this subject has been discussed, I'm quite
glad that most of my central idea made it through unscaved. But, just so
that there is no confusion, I'd like to suggest rereading my post if it is
believed that I was merely restating the laterally orientated femora
hypothesis.>

  The only diversion I recall was to clarify the issue of dogma, which had
been misused before by Kris to label those coming after the original
"dogmatic" view that microraptors/sinornithosaurs can fly or soar or glide
with legs spread outward. This resolves a basic misunderstanding about
anatomy that limbs and joints don't typically stay in a disarticulated
mode without pressure that keeps it there, like the weight of the wren
holding's its legs out. If Kris would like to point out any useless
discussion, then he is welcome to it then just speaking in rhetoric.

<What I actually said was this: > Take the femora and move them forward as
if the animal is sitting in a nest. Then roll the femora so the lateral
aspect of the shaft turns to point in a dorsal direction. This would have
the effect of orientating the distal condyles so that they pointed in such
a way as to allow the tibiotarsus to extended outwards in a lateral
manner. This motion also has the effect of orientating the leg feathers in
the direction of the airflow, which is precisely where we want them if
they are going to be involved in any sort of flight-related activity. < >

  And what I hoped to show was that the femoral rotation can't occur, but
no discussion of this can occur. Such rotation would make the femoral
caput disarticulate from the acetabulum as it now orients VENTRALLY and
not into the hipsocket.

<What is so profound about these birds in relation to my argument is that
these animals are showing a slight lateral orientation of the tibiotarsus
that is used to set up an even greater lateral orientation of the
tarsometatarsus. This is perfect support for two very important ideas
central to my argument. One is the fact that variations occur that can be
selected upon. Two is that this particular posture was most likely induced
by the bird's environment, much in the same manner that the arboreal
hypothesis suggests selective pressure that would have been applied to the
basal dromaeosaurs in question (something that Ralph Miller also noted). I
am also betting that there is little in the way of alterations to the
anatomy that facilitates this ability when compared to most birds of
similar sizes and overall build. This can be tested rather easily with a
little comparative analysis, though I admit the results have little impact
on the issue.>

  As an aside, every bird mentioned by Kris (wrens and bitterns) are
advanced birds with an elevated, spherical femoral caput, and an
acetabulum that faces dorsally, features not observed in
"sinornithosaurs."


<Also, I did not state conclusively that these dromaeosaurs possessed the
ability to laterally sprawled or not. What I did do was ask for exactly
what prevented them from doing so: 

...

These questions were really never answered, and as such, they remain on
the table.>

  Below are posts that mention how many times the femoral eversion thing
was mentioned and shown that given the typical acetabulum as confirmed in
the CAGS specimens of *Microraptor zhaoianus* and in *Sinornithosaurus
millenii,* and the medial, rectangular, non-spherical and non-elevated
femoral caput in CAGS *Microraptor* :

  http://www.cmnh.org/dinoarch/2003Jan/msg00580.html

  http://www.cmnh.org/dinoarch/2003Jan/msg00609.html

  http://www.cmnh.org/dinoarch/2003Jan/msg00713.html

  http://www.cmnh.org/dinoarch/2004Apr/msg00586.html

  http://www.cmnh.org/dinoarch/2004May/msg00075.html

  http://www.cmnh.org/dinoarch/2004May/msg00095.html

  These posts also reflect the times when a scientific, falsifiable
statement was made and it was refuted, showing that Scott and I are both
practicing science and making "if" statements. This does not include my
most recent reply to Kris in which I, yet again, make the selfsame
statements, and David repeats them. So in saying this, "These questions
were really never answered," Kris is wrong, and has been since the
beginning of last year when this topic first came up onto the table and
was argued against.

<To state them another way, do you believe that "tens of millions of
years" of evolution is required to go from what we see in the wren and
bittern, to a laterally orientated tibiotarsus and tarsometatarsus in the
ancestors of our basal dromaeosaurs?>

  Aside from David mentioning once or twice a reference to time and what
someone else said, Kris has been the only person I can recall other than
what is linked to below, who has mentioned "tens of millions of years,"
but is ascribing this to others, for no reason I can say than to try to
discount what has been said.

  Examples:

  http://www.cmnh.org/dinoarch/2003May/msg00119.html ... from Ralph
Miller.

  http://www.cmnh.org/dinoarch/2002May/msg00004.html ... from Mickey, but
this was about troodontid--dromaeosaurid phyletic separation.

  http://www.cmnh.org/dinoarch/2003Dec/msg00552.html ... about character
acquisition over time, from Ken Carpenter, but not about *Microraptor*
specifically.

  http://www.cmnh.org/dinoarch/2003Jan/msg00477.html ... from Jeff Hecht,
about transformation from an *Archaeopteryx* to *Microraptor* morphology,
or the reverse.

  http://www.cmnh.org/dinoarch/2003Mar/msg00291.html ... from Kris himself
on beaks in toothed animals, arguing such time is needed for
transformation to occur in some cases. 

  I decided to stop there, as I think five examples to show that no one
has really brought up "millions of years" into this discussion as Kris
implies has actually occured, at least on this Mailing List.

<And while I'm at it, what anatomical differences are allowing some birds
to laterally extend their legs, while others cannot? If someone knows,
please be specific, since these differences are obviously oh so profound.>

  Paul has actually described some of these, and even implicated
*Microraptor* and *Archaeopteryx* has having them, despite his own work
and that of others, including Hwang et al., show otherwise. However, I
digress: Above, I had written ' [A]dvanced birds with an elevated,
spherical femoral caput, and an acetabulum that faces dorsally, features
not observed in "sinornithosaurs." ' I considered this important enough to
repeat here. These features are implied as being "key" to the ability to
adduct the femur, as John Hutchinson said. I mentioned the ability of
muscles and their arrangement as a constraint, as the soft-tissue restrict
the movement of bones, rather than increase them, and these would have to
be taken into account even in Kris' own "rotating femur" idea.

<Also, who seriously thinks that it took "tens of millions of years" for
these birds to develop this ability?>

  From my research, no one has. Time is largely unimportant in phylogeny
reconstruction, and the timing of morphological development is still
questionable given the lack of any corellation between the genetic and
morpholigal trees in current phylogenetic analyses, linking a
morphological expression to a particular gene and its timing of origin
and/or loss.

<Restating flaws in an older hypothesis, attacking the lack of evidence
for the older hypothesis, giving "just so" answers, or going off on some
tangent instead of answering my actual questions, is simply avoiding the
real issue.>

  This can be described as "flying off the handle." This is bringing in
issues that have not been brought into this debate as being part of it. In
this manner, Kris is making "attempts to sidetrack and manipulate the
argument."

<A claim was made that a soft tissue's purpose is only to restrict joint
movement. This is indeed the case in many ways, but the suggestion taken
as it was stated is quite misleading.>

  So when I suggested it, and someone else read it, they were feeling
misled? My purpose for bringing up muscular and tendinous restriction was
pointed: Kris brought up a reason why soft-tissue was or would be ignored,
for the sake of the bony elements, when this is untrue: the soft-tissue
has in fact, as I described in my last post, a major and in some cases
more important, consideration than the bones. They show there was an
aerodynamic effect in the leg, and the production of a shorter leading
edge and longer trailing edge. As I described, they become a constraint on
what the limbs can do, even though they describe the limbs can do
something more than make the animal run, jump, sit, swim, etc. The wings
alone are enough to control descent, perhaps provide lift, on their own,
so a neccessity to use the legs as lift-production or drag-induction is
unlikely. There is likely an accessory reason, and some have suggested
shading (Tom Hopp), drag-induction (Tim Williams), increase of airfoil
area (David Marjanovic or Greg Paul), as a possible "canard" for
aerodynamic stability (myself, even if they are behind the wing, as in the
Predator's wing design), etc.

<If one has a joint that is deep, like many hip joints are in birds for
example, the thicker the cartilage is, the more shallow the acetabulum
becomes. This can, in many cases, free up the range of motion of the femur
a great deal.  But, in giving more flexibility, it in turn makes it more
prone to dislocation. What's being forgotten here is that soft tissues, as
in ligaments and tendons, can be utilized as braces for a bony structure
that would otherwise become easily dislocated without such support. Again,
this is why I used the manus of *Archaeopteryx* (and the wrist joint of
birds in general) as a key example in the first place. It is almost a less
cruel version of "Arbeit macht frei", in which instead of "Work will set
you free", restrictions that can be used like safety harnesses can set you
free...>
 
  From my dissections in mammals and birds, as I described in my last
post, cartilage largely conforms to the shape of the bone. If the bone is
rectangular, then the cartiage on it will largely conform to this and not
allow the bone to become more curvaceous in regard. Extension of
dimensions, such as any linear direction, via cartilanginous caps or
lining, such as between the femoral caput and acetabulum, do not expand
the dimensions by enough to seriously affect how much adduction or
rotation can occur. Dissecting a few immature bird hips, where cartilage
has a greater proportion to bone than in adults, the cartilage over the
femoral caput is thin instead, and the cartilage in the acetabular wall is
predominantly medial with some thin layers over the bone itself in the
acetabular ring. Mature animals nearly completely ossify this cartilage,
and what is left is a thin layer It would seem there is not much positive
evidence to support cartilage increases the adduction angles.
Incidentally, the presence of numerous tendons and ligaments within the
acetabulum prevent the femur from doing what Kris has described as being
possible in the femoral long-axis rotation to turn the internal "knee"
angle laterally.

<Given the replies already received, saying that there is zero evidence in
the fossils that prevents a sprawling posture from being possible after
taking variations in the form of soft tissues into account, has yet to be
sufficiently countered.>

  This is untrue. Arguing that the femur cannot dislocate or move in a
condition that prevents it from orienting other than what is seen
otherwise in nature for animals with similar femora or as much as
biomechanics would appear to permit is a falsification to the hypothesis
that the femur CAN evert or somehow rotate 90 degrees around its long axis
and remain in articulation. As John Hutchinson and myself have said
before, as I believe has Tom Holtz, the bones are in two dimensions, not
three, and the argument for shape of the elements diffult to make into
three dimensions. However, certain inferrences can be made:

  1. The acetabulum lacks a medial wall.
  2. There is no supra-acetabular crest.
  3. The ilium is not narrower above the acetabulum, but is as broad as at
the pedunculae.
  4. The femoral caput is oriented medially or more medially than
projected dorsomedially.
  5. The femoral caput lacks a rounded distal end, and is rectangular in
aspect.
  6. The trochanteric crest is elevated above the femoral caput.
  7. There is no femoral "neck" between distal caput and shaft.
  8. The femoral shaft is largely straight in cranial/caudal views.

  To make these mean something beyond yakking: *Microraptor* has 1, 4, 5,
6, 7, and 8; *Sinornithosaurus,* almost inarguably *Microraptor*'s closest
relative, has 1, 2, and 3, and while the femoral caput is preserved in the
*S. millenii* holotype, 6, 7, and 8 are unknown due to overlapping,
crushing, or possible distortion, and Paul argues it  lacks 4 and 5;
ratites, galliforms, and other primarily terrestrial birds lack 1, 3, 5,
6, and 7, and have 2, 4, and 8; and most arboreal birds (from which wrens
and bitterns derive) have 2, and lack 1, 3, 4, 5, 6, 7, and 8. The
hypothesis here thus argues that this pattern provides that the presence
of the conditions above prevents femoral adduction and rotation for any
effective purpose, and that lacking them would permit this condition,
including the ability to adduct the femur about 30-45 degrees without
pulling on the medial abducting musculature (from both a horizontal and
sagittal plane); lacking these features would prevent femoral adduction in
this manner. The legs were likely only capable of splaying out 10-20
degrees before bony stops in the limbs prevented further movement.

<Again, my whole point with all of this is that the conclusion that the
issue of the lateral sprawl is an open and shut case is highly premature.
Instead, it is really just the glimmer of old dogma intruding into what is
supposed to be a science. Harsh words, but truthful words nonetheless.>

  I have been vigorously practicing science in this discussion, much to
the question of some I am sure. I would think this practice of science
should include refutation to "clean" hypotheses as much as forming
hypotheses from purely positive evidence. One goes too far in one
direction (affirmation through positive evidence) and becomes blind to the
other (refutation through positive evidence).

=====
Jaime A. Headden

  Little steps are often the hardest to take.  We are too used to making leaps 
in the face of adversity, that a simple skip is so hard to do.  We should all 
learn to walk soft, walk small, see the world around us rather than zoom by it.

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


        
                
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