Re: A note on pterosaur nesting behavior

[David Peters <davidrpeters@charter.net>]

> Are we certain of this?  I'm skeptical of "can't get there from  
> here" arguments.  If it is correct, then there is still the issue  
> that we need evidence for ovoviviparity, first.  Not sure what you  
> were trying to indicate with the comment about desiccation.  Living  
> diapsids with weakly calcified eggs combat desiccation through  
> burial - so the Grellet-Tinner et al. hypothesis would actually deal  
> with that problem, as it is.

Burial within the mother works just as well.
> > Megapodes have long incubation times.
> > Birds with short incubation times don't fly immediately after  
> > hatching.
>
> As a general rule of thumb, this is true (though not a hard and fast  
> rule).

I think we have to go with general rules here.

> Either way, we don't know anything about incubation times for  
> pterosaurs.  I suppose you're arguing that if they were  
> superprecocial then it is likely that pterosaurs had long incubation  
> times.  It's not a bad concept, though I have no idea how'd we would  
> confirm or refute it.  Supposing that we did, though, it really does  
> not speak to the egg burial issue, anyway, because incubation times  
> among species that bury eggs vary enormously.  Some are very long  
> indeed (200+ days for some turtles, for example).
You just confirmed it. If they're fully developed and started off as a  
single cell, they HAD to have had a long incubation period.

It would be nice to find a baby inside. We haven't found one yet, but  
I don't think we've looked very hard either. At that scale, gastralia  
could look alot like wing bones. Other than the skull, most of a  
pterosaur looks like a package of pickup sticks.

Okay, Mike, let's take your scenario. Burial in sand? Leaf litter? Mud?
How deep do the eggs have to be to avoid the dry layer on top?  
Remember, this is going to be a long incubation period. As long as  
that of a megapode.
Okay, now they're hatching and clawing their way to the surface. Do  
the babies do this with wings extended? or folded? Serious question.  
No living reptile has such long limbs.

One final thought. If buried within the mother, and the mother happens  
to have an elevated metabolism, are the eggs going to incubate more  
evenly and perhaps more quickly? All in all, it's just more  
parsimonious. Especially since pterosaurs are the furthest thing from  
archosaurs.

Dave


> --Mike
>
>
> Michael Habib, M.S.
> PhD. Candidate
> Center for Functional Anatomy and Evolution
> Johns Hopkins School of Medicine
> 1830 E. Monument Street
> Baltimore, MD 21205
> (443) 280-0181
> habib@jhmi.edu