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RE; my comments on John Damuth's neat research. I haven't seen the paper yet,
but I suspect it should be done or coming out soonish - he gave his talk
on it about 9 months ago, as I recall. John is a good publishing machine, so
I'd be surprised if he doesn't have it in press already.
I think egg number and body size do correlate positively in vertebrates, and
even in tetrapods (and just about everything else withi groups) - which is
one the good things about getting bigger - you can dump more offspring out
and still retain energy to maintain the egg producing factories. In fact,
what keeps many things like crustaceans from all getting bigger in their
lineages is that predation pressure for many taxa increases as size gets
bigger. Back to tetrapods - I surely would like to know of or see a review of
body size/egg size relationships.
John used distributions of species frequencies versus body size to show
that dinosaurs have a very different distribution than mammals, with some
additional data I don;t remember to talk about stress and safety factors
(age is a depressing thing, sometimes your memory goess... What was I talking
I can;t recall the classic reasons for the relationship between body size
and gestation period - which also has links into the really chaotic
r- and k-selection discussions - but I'm sure someone more physiologically
informed than I am can dredge them up.
Anyway, I think the scenario is that large dinos probably produce more
eggs per nest, and possible more nests per unit time, than other dinos
and, consequently, the larger you are, the more potential next generation
dinos there can be. Perhaps you needed lots of baby sauropods to make it
to the huge size and be more predator resistant - even with supposed
parental care and herd structure, etc. which is up in the air. I think if
the stress/gestation period limits were not there for mammals - then you'd
see a lot more larger mammals relative to the number of smaller ones.
Anyway, more thoughts from a placental mammal (although actually I
don;t personally have a placenta). Certainly, I don;t think any way
is inherently superior, both are probably a good idea at different
times for different sized taxa.
Mammalianly Yours, Ralph Chapman, NMNH