Tail Shape in Archaeopteryx

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

Concerning tail shape in *Archaeopteryx*:

  Though studies on the aspect of the tail as a comparative lift-generator
(Burgers and Chiappe) and in regards to it's use as a steering mechanism
(Martin, as well as Chatterjee), I think one should look at the difference
between a flying squirrel's tail (take *Glaucomys volans*) and that of the
roadrunner (*Geococcyx californianus*), the latter having been compared
well in the public as well as in the literature (take Feduccia's book and
Martin, for instance).

  Though both tails are long, they have a different shape, as well as a
different mechanical structure. The tail of the rodent in reference is
long, and the sides of the hairs evenly long cranially and caudally,
producing a generally even width along its length. They do not typically
vary in width during use except when at rest. From visuals of watching
flying squirrels leap and glide, it appears to me that it requires air
pressure to expand the tail hairs. The tail is used for steering, and the
bony tail is relatively stiff, though more flexible than a
dromaeosaurid's.

  Comparatively, the tail of the roadrunner is typical triangular in
shape, and widens in flight, increasing the width of the distal end. This
is controlled muscularly, and birds which employ the variability of the
width of their tails (see work by Gatesy on pigeons) use this to control
lift to some degree, and affect pitch.

  So what compares best with *Archaeopteryx*? The tail is similar
generally to the flying squirrel in being generally evenly wide along it's
length, though wider distally than proximally (as in the resting state of
the roadrunner's tail), and if the feathers could expand, unlike the
roadrunner's tail they would ratain the same aspect, only broader in
perimeter than previously. That is similar to the squirrel's tail, but
unlike the roadrunner's, which changes aspect in and during flight, as do
other birds'. The tail is stiffer than the squirrel's, though: no
articulated tail of *Archaeopteryx* is curved greater than about 2 degrees
of an arc in the middle, up to about 5 in the distal end. This suggests it
was more capable of dealing with stresses than the flying squirrel's was.

  So what was going on? I'll leave the floor open...

=====
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.

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