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Re: Dino dimorphism (Was More tyrant Q & A's)




On Thu, 10 Dec 1998, chris brochu wrote:
> (There are some other complications - for example, the size
> difference in living raptors diminishes with (a) the amount of carrion in
> the diet and (b) the amount of time spent on the ground rather than flying.

A study of weaver birds finds great correlation between dimorphism and
diet.  Perhaps the suggested reasons apply to non-avian dinosaurs.
Seed-eating birds cannot protect resource.  Therefore, selecting a male
for protection value (ie., one that will stay around) is pointless.  The
female may as well go for the most attractive male--the guy with the
brightest feathers, any trait that might be of some value to her
offspring.

Weaverbirds in the forest which eat insects can guard a
patch--a tree, for example, against interlopers.  So a female should pick
a male based on his staying power, not so much his plumage.  Anyway,
dimorphism also correlates with mating system such that species with
greater dimporphism have greater polygyny--I think this is a fairly close
correlation. 

So, it might be possible to say that this or that dinosaur has this or
that sort of mating system.  i'm sure others have done this.  I'm sure it
is fraught with difficulty.

Looking at Chris' example of the raptors eating carrion: one could
hypothesize that  a lady raptor would appreciate the help of protecting
carrion and keeping it for themselves, i.e., a team of two might get more
than twice the amount of food than an individual.  Whether this is true or
not I don't know.