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Sauropod live birth - maybe



Jennifer and Dave champion the idea of sauropods popp'n sprogs...Making 
the astute observation that BROWSERS (no such thing as Mesozoic grazers) 
need to cover a large geographical area, seemingly incomptable with 
tending a nest.

Consider, though, the following...

 - Hadrosaurs laid eggs, browsed, and still reached pretty large sizes 
(implying a high volume of food intake).
 - Nesting birds manage okay, usually with both parents helping out 
(taking turns to feed and attend nest).  Birds are lucky - the early 
laying of the eggs (with the female's investment being not much larger 
than the males up until laying happens) means that the female is not so 
susceptable to being left with the baby, encouraging paternal care to 
continue.  Mammalian females, however, are the victim of their own gestation 
period - the male has plenty of time to go off and find more mates, and 
an abandoned female has to wait until she comes to term before she can 
ditch the offspring and look for a more faithful mate...by which time it's 
not worth her while (hamsters seem to be able to abort unwanted 
offspring, though). Thus in most mammals the female gets exploited into 
doing all of the 
work, the male contribution ending at a few sperm (we are a notable and 
politically correct exception).  Hence the need for herbivores to have 
precocious young, so the young can move around as soon as possible  after 
birth, and the female's eating habits are interupted for the minimum 
possible time.  Carnivores, in contrast, have altricial young (dependent 
on mum for a  long time) because the nutrional demands on carnivores are 
less urgent.  A herbivorous egg laying sauropd, more likely to be like a 
bird and have two parents helping out, need not suffer any of the 
problems commonly encountered by mammalian females.  Your analogy with 
giraffes may be apt physically, trophically, and aesthectically, but not 
reproductively!

 - Alternatively, the huge difference in mass between a mother sauropd 
and her eggs (likely to be smaller than that of the elephant bird) allows 
the possiblity of huge numbers of eggs at a time.  Which puts it way over 
to the r end of the reproductive spectrum (like toads who spawn lots) rather 
than the K end at which you find most mammals.  So maybe they didn't 
bother with parental care, figuring that at least some of their low cost 
eggs would survive anyway.  Again, no problem for dinner menus (at least not 
compared with large herbivorous mammals).

Never forget the huge range of different strategies that Nature uses to 
achieve a small set of goals (adequate reproduction, thermal regulation, 
food intake, predator avoidance are four major goals).  Groups such as 
mammals or birds only ever use a small set of combinations of those 
strategies.  Dinosaurs may have been similar to birds or mammals, or 
crocs or turtles, in the set of strategies they used.  But they may also 
have combined those strategies in ways that don't exist today.  There is 
no need to always make dinosaurs the same as mammals to make them work 
for us.  They will do quite well enough as dinosaurs.

Sermon over.


Colin McHenry

It all looks the same in the swamp..


P.A.Swamps Inc.
aka. Vertebrate Palaeontology Labs
U.Q.
Oz

we aint geologists, that's for sure