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Resend: turtle vs. Titanosaur (was Gigantism...)



On Sat, Feb 19, 2011 at 8:52 AM, John Bois <mjohn.bois@gmail.com> wrote:
> On Mon, Feb 7, 2011 at 12:57 PM, David Marjanovic
> <david.marjanovic@gmx.at> wrote:
>>>  Some (Loggerheads) in the Sargasso sea. Terrestrial analogue?
>>
>> Any thick vegetation? I don't know...

But...turtle hatchlings do have a rather thick shell for protection.
This would put dino hatchling predators at an advantage relative to
those of turtles inasmuch as you would have to be bigger relative to
your prey to crunch the shell. In dense habitat this gives turtles the
advantage.

>>>  2. Because of water access, they can _and do_ lay in places with
>>>  reduced predation pressure. Can't think of a place Titanosaurs could
>>>  get to that their predators could not.
>>
>> The predators of adult titanosaurs are rather irrelevant to their eggs, I
>> suppose.

I love cashew nuts...their small size doesn't protect them.

>>>  3. Not sure of specifics here but would bet that sauropod eggs'
>>>  optima were more stringent than those of turtles.
>>
>> Why?

Embryo race against plunder because nests not hidden (Titanosaur
nests, at least, were shallow it seems...big nesting signature
relative to secretive turtle strategy); if parents stayed, shorter
incubation time (i.e., thanks to great gas conductance relative to
turtle eggs, means less stress at the rookery; lower sa/vol ratio of
big eggs requires faster diffusion rate across shell and membranes;
shelled eggs (primitive in dinosaurs?) give greater protection aganist
disturbance and provide needed gas flow with porosity; bigger eggs
cause bigger build up of CO2 requiring more effective means of
clearing it with either parental care, greater porosity, fewer eggs,
shallower burial or all of the above; Do we know from embryos which
had the faster growth rate? A faster growth rate necessitates more
stringent optima, right?