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RE: T rex brooding



Dwight Stewart wrote:

<If its arms were entirely useless, then why didn`t evolution
eliminate them altogether?>

  Probably because they weren't entirely useless. Instead of rendering
the digits totally vestigial, the adaptive process of evolution
enabled tyrannosaurs to reduce to two, and those two fingers became
highly mobile, with joints at the metacarpals that gave it a
spreading-when-extended and narrowing-when-flexed range of motion. It
was a specialized hand.

<Even with limited flexion at the "shoulder joint" (or perhaps, nearly
none!) that's enormously strong for a 'human sized' limb.>

[snip ...]

<IF the tyrannosaur forelimbs were as strong as some infer, that would
seem to work in favor of 'breasting'.>

  The humerus was limited to about 30 degrees of fore-aft movement,
most of it centered on the veritcal.
  The elbow was limited to a 20 degrees or so off the vertical to
strait forward and perhaps 10 degrees above the horizontal.
  The wrist could twist a little (I think) and could still bend up and
down rather well, plus the fingers were mobile [above].

  It could lift, but could not "brood" with the arms simply becuase
they were not long enough to cover anything unless the chest were
firmly down on the ground, and then _that_ would be a rather awkward
situation, wouldn't you say?

  The rather surprising conclusion (from a few members on the list
whose names, but for the esteemable Dr. Holtz' and perhap Ralph Miller
III, I can't seem to remember) that I see is that these were like
little chain hooks, to latch onto brush and debris and drag it to the
nest, or prep the mound, build it up, perfect it and hang the
curtains, a task that probably took days, would actually be
accomplished well.

  The animal wouldn't even need to lay its chest down to do any of
this, just tilt the forequarters down and twist the head sideways so
it can see below it (a little, I'm sure) or do it by feel, if at all.

==
Jaime A. Headden

Qilong, the website, at:
http://members.tripod.com/~Qilong/qilong.html
---
All comments and criticisms are welcome!

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