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Re: Segregated vs age-mixed sauropod herds

On Mon, Mar 15, 2010 at 12:54 PM, Mike Habib <habib@jhmi.edu> wrote:
John bois wrote:
>> In any case, the trend in amniotes seems to be
>> toward the evolution of more not less parental investment in
>> offspring--or, should I say, investment in fewer high quality babies.
>> This makes nest-guarding more of an imperative.
> Is there any test to demonstrate that this is the case? ÂCasual observation
> suggests that the only places where this trend might be robust is in a few
> clades of mammals. ÂEven then, it's just casual observation - rigorous
> testing might very find that these trends are not significant. ÂIn fact, I
> hypothesize that many lineages of amniotes, if tested rigorously, will show
> exactly the opposite trend.

I am thinking of very broad trends: animal body plans and strategies
evolving most recently indicate higher parental investment: placentals
compared to monotremes; birds compared to basal dinosaurs; archosaurs
compared to lizards. Indeed, the amniotic egg itself is a quantum leap
in investment compared to amphibian reproduction. Is this scale too
broad to be useful? I don't say this is any kind of rule like voodoo
Cope's Rule...more a trend. And again, r selected species are doing
just fine.