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Re: A note on pterosaur nesting behavior

On Jul 24, 2009, at 11:21 PM, David Peters wrote:

Two words:



Mama carries the eggs until just about to hatch. Babies fly free shortly thereafter. Very little down time where anything could get to them.

It's an interesting scenario, but what's the evidence for it? Incidentally, ovoviviparous lizards and snakes tend to have very weakly calcified eggs; even more so than Grellet-Tinner suggest for pterosaur eggs based on preserved microstructure. I also note that no pterosaurs have been recovered with embryos inside (as has occurred for mosasaurs and ichthyosaurs), but we do find a number of cases of pterosaur eggs preserved without bits of mom. If they were retained for pseudo-livebirth, we might expect a different pattern.

This scenario cannot happen with archosaurs. Bottom line. It's not in their gene pool.

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.

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). 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).


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