Re: Segregated vs age-mixed sauropod herds

[don ohmes <d_ohmes@yahoo.com>]

--- On Mon, 3/15/10, don ohmes <d_ohmes@yahoo.com> wrote:
 
> "Finally, although nest attendance may be inferred by
> phylogenetic bracketing (all living archosaurs attend their
> nests), the large size of adult
> titanosaurians and the proximity between egg-clutches
> suggests little or no parental
> care, an inference consistent with the absence of evidence
> of trampling." -- from Chiappe,  
> 
> <http://dinosaurs.nhm.org/staff/pdf/2005Chiappe_et_al-Paleovertebrata.pdf>
> 
> Chiappe does not address the case where the nests are in
> 'patches' w/ an effective radius of <1 neck length, which
> would allow direct tending /w the mouth, perhaps even by a
> single sentry. 
> 
> Implied by such close proximity is 'turn-taking' in terms
> of nest-building, and nest locations that are closely
> defined by the previous nesters. Which in turn implies
> social order, perhaps hierarchy, and keen instinctual
> awareness and avoidance of the nests of others. Quite
> remarkable, IMO, "nest attendance" or not...

Visualizing the nesting process, again assuming the rookery scenario is 
correct: once a multi-nest 'patch' was been established, how does a female 
ready to lay her eggs add her nest to it? 

"Building" a depression with the head from a safe distance seems 
straight-forward; but then this huge animal had to turn, put herself into 
reverse gear, and position herself over the depression, keeping the tail clear 
of the ground to avoid disturbing other nests, and deposit the eggs with 
reasonable accuracy into it. Perhaps the mouth was then used to place any 
misdirected eggs into the depression as the site seems to speak against any 
scattering of eggs.

In the counter-intuitive case where the depression is built with the large 
feet, accuracy is still an issue, and the head would likely be needed to remedy 
any poorly-aimed eggs. These depressions were very small (=<1m in diameter?) 
relative to the size of the animal, unlike a turtle nest, wherein a miss is 
mechanically unlikely. And they are also very tightly packed, relative t
areful egg laying in broad daylight!" Although I am not at all sure about the 
need for daylight.

Anyhow, The speculation that head-size was constrained by reproduction in the 
mega-sauropods doesn't seem implausible to me. Or testable.

Are there other, less "demanding" interpretations of the Auca Mahuevo site? Any 
experts out there have an accurate idea of the distance between the nests 
expressed in track diameter?