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Re: [Re: The Cretaceous Middle-East]



Dan Bensen wrote:

<Tyrannosaurs had babies that were very gracile and
coelurosaur-like,>

  Perhaps written in basic morphotypes, but as Tom
Holtz will tell you, this would be because
tyrannosaurs _are_ coelurosaurs. And also back to
basic biology, in an ontogenetic sequence, younger
forms will resemble more "primitive" forms. I think I
can easily concieve of *Stokesosaurus* and *Itemirus*
as coelurosaurs, but the basic resemblance to
tyrannosaurs proper may be due to a large part on the
plesiomorphic nature of these forms, and perhaps the
plesiomorphy of tyrannosaurs ... but because
*Iliosuchus*, *Stokesosaurus*, and *Itemirus* have not
so far been published in a comprehensive modern
anatomical comparison, this is unquantified.

  Typically, small coelurosaurs are very gracile,
long-legged (exception: *Ornitholestes,* femur is
longer than tibia and legs short generally) forms with
largish heads, long tails, etc.. Very general.

-------

  Meanwhile, onto the main theme:

  Selection pressures for large size would usually
concern food: less food, more competition, shrink to
maximize intake and engery provided thereof, defensive
strategies, and the smaller critters will be better
equipped militaristically; more food, forms tend to
congregate, as seen in several extant biomes such as
the Serengeti, North American Northwest, and eastern
coastal Pacific. Competition will also increase
between predators, interactions due to more predators
(=more food) so behavioral strategies develope. This
is not comprehensive, and plenty of exceptions. Modern
Arabia has its predators and prey species, including
oryx, ostrich, jackals, lions, etc. Some have been
outcompeted or wiped out by man, but still this
constitutes a modern biome as much as it extisted two
hundred years ago or more recently.

  To introduce an unquantified entity into a biome
that is intended to occupy a niche already occupied,
one must wipe out the previous niche holder
(naturally, outcompete), or adapt to exploit the niche
by region, rather than general. Different forms of
jackals, different regions of jackals. Vultures in
Arabia are prevalent, both as predators and
scavengers, including some infamous bone-crushers like
the king vulture and lammergeier (one of the prettier
vultures). In other habitates, we have wolverines or
hyenas that occupy this role. And Samoan
bone-breakers. But that's only an art I'd like to see
in the Olympics.... :)

  As for oviraptorosaurs in water, Barsbold proposed
in 1977 that they were amphibious (his words, not
mine) molluscivores, so you can easily adapt a
shoebill--merganser morphotype from them, in easier
steps I would think than making dromaeosaurs into
birds. Also recall that in southern Arabia, there are
no major rivers, very few minor rivers, and all rivers
and streams are transitional in both space and time,
so any major aquatic form would have to be pelagic or
shore-forms, or just seasonally fluvial, as in
non-*maritimus* bears.

  That's enough for now....

=====
Jaime "James" A. Headden

  Dinosaurs are horrible, terrible creatures! Even the
  fluffy ones, the snuggle-up-at-night-with ones. You think
  they're fun and sweet, but watch out for that stray tail
  spike! Down, gaston, down, boy! No, not on top of Momma!

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