Re: coelurosaurs Allosaurus-like

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

Ken Kinman (kinman@hotmail.com) wrote:

<But I would assume a robust tibial width isn't the only factor, since some 
dromaeosaurs also have
relatively wide tibiae.>

  Unlike Ken, I consider some hindlimb features very valid, simply for 
distributional success at
polarizing them and their prevalence across a wide range of intra-specific 
specimens. One of these
is not the width:length ratio, which changes relative to cursoriality or the 
absence thereof; the
dimension in quadrupeds alters depending on degree or actuality of 
graviportality, mediportality,
etc.; it is also relative to digitigrade, plantigrade, or unguligrade feet. In 
dromaeosaurs, which
in some forms the tibia _is_ relatively short, as in most oviraptorids, the 
width:length ratio is
relatively small and similar to other non-coelurosaurs. This is especially true 
of therizinosaurs,
in which the tibia has an index similar to basal sauropodomorphs and some 
ornithischians which are
not cursorial. However, dromaeosaurs secondarily reduce the length of the tibia 
relative to
mid-shaft diameter [width if you will] the further crown-ward they are. Basal 
dromaeosaurs have
very elongated tibiae (*Microraptor*, *Sinornithosaurus*, etc.] whereas the 
larger the form, the
shorter the tibia relative to diameter [*Deinonychus*, *Utahraptor*, etc.] and 
some [e.g.,
*Velociraptor*] fall in the middle. Simple metric relative to size in these 
forms, it would
appear, and this is true even of the most derived dromaeosaurs [*Utahraptor*, 
and it would appear,
*Achillobator* as well, which can be interpreted as an "advanced" dromaeosaurid 
or something quite
similar but having a rather derived, un-advanced [relative to birds] pelvis and 
hindlimb.

=====
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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