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Re: Theropod infanticide -- speculations



Sorry all for the somewhat belated repsponse, but I've been traveling this
week, and have only gotten to a computer today.
>Using the remarkable Coelophysis Ghost Ranch specimens as a fulcrum<
Indeed it is a remarkable collection of animals (and not just _Coelophysis_,
which is also often overlooked)...but be careful what you're extrpolating
here...

>One can, with a minimum of effort, advance a scenario for Coelophysis<
More than minimum effort is required for the GR Quarry, actually. Its a very
complex system, and I for one, am not certain that the collection of
_Coelophysis_ represents how the animals behaved under normal conditions.

>(the only theropod found in sufficient numbers to qualify as a colony,  in
one location, to enable age-growth interpolations).<
Age-growth/sexual dimorphism studies, etc. are all possible from the GR
Quarry, but we must be certain this actually was a natural population, and
not an accumulation due to extrodinary circumstances (both pre- and
postmortem).

>It has been speculated that, in times of environment stress (e.g., a
drought), infanticide was common among these taxa<
Its key to this argument for cannibalism to actually be the explaination for
what we see in the famous AMNH specimens...see my comments in the archive
for thoughts on this subject...a paper is also in prep on this, so hopefulyl
a more clear and concise explaination will be availible somewhat soon.


>needed nutrition for starving, larger individuals, including females who
would obtain new nesting sites in the process of eating the hatchlings (and
possibly killing and eating smaller breeding females).<
We'd need to, beyond the point above, be able to determine which sex is
which. Sexual dimorphic determination may be possible, but I doubt that we
would be able to determine sexes based on fossil evidence.


>Colonies of Coelophysis resulted not because BBC film crews from the
Discovery Channel were nearby and needing an easy shot<
But perhaps because of the availibility of food, or water, or fleeing a
volcano, or a giant was wandering throught the forest behind them. This is
most certainly not a breeding grounds area (a riverbed filled with other
predators!), and may not even represent how these animals behaved in
reality.

Moreover, one can ask if field notes on the Ghost Ranch Coelophysis can show
distribution of females within the colony, the colony itself being a
theropod breeding strategy (females suppressing their own breeding to
co-parent offspring of dominant females).<
I would be surprised if the field notes from GR showed where all the blocks
were taken out. From what I've seen/gathered, the notes/maps/etc. from GR
aren't the most detailed in the world...
It is also pertanent to this discussion to note that AFAIK, only TWO (the
famous AMNH specimens) show evidence of "cannibalism"...and one is a robust
morph, while the other is a gracile morph...so whatever was going on there,
it crossed theoretical gender boundaries.
Peace,
Rob

Student of Geology
Northern Arizona University
P.O. Box 20840
Flagstaff, Az. 86011
http://dinodomain.com