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RE: Segregated vs age-mixed sauropod herds



--- On Mon, 3/15/10, John Scanlon <riversleigh@outbackatisa.com.au> wrote:

> "Never underestimate the stealth abilities of snakes" -
> assuming the
> sauropods piled some sort of soil/vegetation mound over the
> eggs (which the
> paper supported based on density of pores in eggshell,
> though this could not
> be confirmed geologically), it would have been relatively
> easy for snakes to
> move around the nesting area under cover. 

Evidently the porosity at Auca Mahuevo supports the uncovered interpretation. 
Eggs were 14cm and relatively thin-shelled...

Comparison of water vapor conductance in a titanosaur egg from the Upper 
Cretaceous of Argentina and a Megaloolithus siruguei egg from Spain -- Frankie 
D. Jacksona, David J. Varricchioa, Robert A. Jacksona, Bernat Vilab, and Luis 
M. Chiappe

"We calculated water vapor conductance (a product of eggshell porosity) from 
the first definitively identified sauropod egg (Megaloolithus patagonicus) from 
the Auca Mahuevo locality in Argentina. We then compared the results with those 
from M. siruguei (an egg type long associated with sauropod dinosaurs) from the 
Pinyes locality in Spain. The 14-cm Auca Mahuevo egg has a thinner eggshell and 
47 times fewer pores than the 22-cm M. siruguei specimen. The resulting water 
vapor conductance (GH2O) of the titanosaur and M. siruguei eggs is 341 and 3979 
mg H2O dayâ1 Torrâ1, respectively; these values are two and ten times greater 
than in avian eggs of comparable size, but lower than in eggs of most modern 
reptiles. Clutches from Auca Mahuevo typically contain 20â40 eggs; in contrast, 
M. siruguei clutches from the Pinyes site average nine eggs. The GH2O of M. 
siruguei exceeds that of the Argentine egg by an order of magnitude, supporting 
previous
 inferences of egg burial. The GH2O of the Argentine titanosaur egg closely 
approximates that of Troodon and some oviraptorid eggs, previously calculated 
as equal to or two times greater than, respectively, the GH2O of avian eggs of 
similar size. Higher embryonic growth rates (relative to modern reptiles), 
especially in some dinosaurs with large clutch mass, may have required 
incubation in a more open environment, where water conservation represented a 
more critical factor than in a buried clutch. The lower GH2O calculated for the 
two megaloolithid eggs is consistent with previous interpretations of nesting 
mode that are based on site taphonomy and nesting traces. This study indicates 
that at least some dinosaurs did not fully bury their eggs."

Accepted: November 2, 2007