Re: Spinosaurus's sail

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

Tracy L. Ford (dino.hunter@home.com) wrote:

<I just looked at my drawing of Spinosaurus and was wondering
why mine and B. Krzic. Then it dawned on me, the angle of the
neural spines. He has them all drawn vertical, in stromer many
of them are angled forward. I don?t believe that they were
modified during fossilzation. Sereno also has them drawn
vertical, which I think is incorrect. I believe (as do some
others) that the front dorsal neural spines tilted slightly
forward, than went vertical. Some back ones even have a slight
curve to them.>

  I have to agree with Tracy, though I haven't seen Beri's
reconstruction...

  There are several elements that have a strong orientation of
the spine below vertical, especially the most cervical-like of
the dorsal neural spines (of which there are three) that point
forward. This is often lost in reconstructions, and even the JP3
spinosaur has all vertical spines.

  Just seeing Lapparent's reconstruction (the first) should put
this in perspective. Based on Stromer's figures, and Tracy's
excellent photocopies of them, I cannot see any breakages, or
distortions that accout for the tilt, and if arrayed by neural
arch morphology (excluding the spines) one gets an idea of how
the spines themselves were oriented into a real fan-like,
radiating pattern...

  The one really backward pointing spine seems to fit the
orientation of the caudal and sacral neural spines, which
considers that it has not been unduly distorted through
diagenesis; the diagenic distortion appears to have occured on
the sagittal plane instead, making the spines warped, and
possibly making the centra unnaturally oval.

  Both tracy and I advocate a more anterior placement of the
tallest spine, instead of just in front of the hips. Instead,
there are shorter spines with distally craniocaudally expanded
spines that match the form of the posterior dorsals, sacrals,
and caudals of Baryonyx, and Suchomimus, that offer much
different approach to the appearance of the "sail" in this
animal.

  With all due respect to Tracy the Dinosaur Hunter,

=====
Jaime A. Headden

  Aaaaaaaaaaaaaaaaaaaahhhhhhhhhhhhhhhhhhr-gen-ti-na
  Where the Wind Comes Sweeping Down the Pampas!!!!

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