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Re: Theropod eating and attacking

I previously Stated:
>I can?t see theropods turning quickly like cats or dogs when they
are chasing prey.
Dann Pigdon replied:
>>Can't you imagine dromaeosaurs manouvering quickly? But then
again their pubes are different to those in your example.>>

   Unfortunately, I want to believe they were as quick and as
manouverable as mammals but it sometimes clouds my thinking.

WMattTroutman added:
>>And I can see theropods turning quickly after prey, that's what the
tail is for!>>

   As I see it, theropods differ from most mammals by running on 2
legs, having tail based muscles (caudo-femoralis) to retract thighs,
and hips fused to backbones.
   When my dog  wants to turn fast (while at a fast gallop) she sets
her front paws to one side and rotated the flexible back to the other
side so that she can accelerate in the direction she wants to go with
out slowing down the stride frequency.  She can change back easily.
   A theropod can not rotate the hip easily relative to the body because
they are fused.   Pubic bone based (and possibly other hip) muscles
probably rotated the leg relative to the hips but not enough for a sharp
turn.  Throwing the tail to one side would also require the body to rotate
somewhat to the same side to conserve angular momentum (I think a kangaroo
tail does this in a vertical direction to keep them from doing back
flips).  This would be in a direction that they do not
want to go.  The caudo-femoralis may then be in the right direction, but
the hips wouldn?t.
   Instead, I think theropods would have to get their legs forward and
lean into the turn, turning in a long radius.  Sharp turns would occur
after a rapid deceleration followed by a quick turn and a rapid
   Ostriches and people I have observed have fused hips and slow to turn
or turn on comparatively large radiuses at full speed.

PS   I have wondered if Coelophysis absolutely had the young in its
stomach or the young was buried against a parent along with all the others
from Ghost ranch.  Are we also certain Compsognathus had a skeleton of the
Lepidosaur_ Bavariasaurus_ in its gut, not just the proximity.

Mark Shelly     Mark Shelly