--- Charles Deeming
<charlie@...> wrote:

> What you saw was a situation that is very common in
> crocodilians. The extraction of calcium from the
> shell makes the connection between the calcite
> crystals and the fibrous membrane very fragile and
> in well developed eggs (crocs and birds) whole
> sections of shells can come away at external pipping
> to reveal the soft fibrous membranes below.

Maybe the filmmakers removed much of the hard outer
shell leaving only the inner membrane for us to see.



> The croc
> then pushes its way through the membrane and
> literally walks out of the shell. This would give
> the impression of a soft-shelled egg.
>
> I have David Attenborough's works on DVD - which was
> the one you saw and I'll look at it.

I'd be very interested to see what you think of it.
("Living with Dinosaurs".)


>
> There are no soft-shelled crocodilian eggs - I spent
> 2 years of my life studying development in
> crocodilians.

A reliable authority is so reassuring. There are too
few around these days :-) . I'd like to pick your
brains on scute development sometime.

I've found your photo of a full-term alligator in its
half egg (in Andrews' "Patterns of Embryologic
development") and it certainly shows a hard shell.

Does this mean that croc eggs are hard when they are
laid or do they become harder? An egg that hardens
after laying would resolve some issues around dropping
them onto earlier laid eggs.

Cheers,

John J.



>
> Charles
>
>
> ----- Original Message -----
> From: John Jackson
> To: Palaeoology@...
> Sent: Wednesday, May 23, 2007 4:39 PM
> Subject: Re: [Palaeoology] Croc eggs sometimes
> soft
>
>
> YeahButNoButYeahButNoBut....
>
> Thanks for that, Charles. Well, now I really don't
> know what's happening, because I was so shocked I
> stayed up to watch it all over again on the "+1"
> channel, and checked it really was a little croc
> emerging and not some lizard thing, and it really
> really was a croc. There's no mistaking the head
> sometimes. Actually, I'd say it was almost
> certainly
> not an alligator, to my eye.
>
> FACT: Either I am going mad or at least one
> species
> does emerge from soft shells!
>
> I suppose the next stops are Sir David, who has
> always
> been kind enough to reply to me in the past,
> though
> I've never actually got anywhere with my enqury,
> or
> London Zoo. Or whoever has been present when every
> species of the group has hatched.
>
> Yours in despair,
>
> John J.
>
> --- Charles Deeming
> <charlie@...> wrote:
>
> > Crocodilian eggs are hard at oviposition having
> been
> > calcified en masse in the oviduct. Attenborough
> got
> > it wrong (not often but it does happen). I have
> > worked on and hatched alligator eggs and they
> are as
> > hard as porcelain! This is true for ALL
> crocodilian
> > eggs.
> >
> >
> > ----- Original Message -----
> > From: John Jackson
> > To: Palaeoology@...
> > Sent: Wednesday, May 23, 2007 12:55 PM
> > Subject: [Palaeoology] Croc eggs sometimes soft
> >
> >
> > Last night I saw (again) an old David
> Attenborough
> > program called "Living with dinosaurs", a
> dreadful
> > name since it was about crocs, chelonians and
> > large
> > lizards, but it did show absolutely
> unambiguously,
> > a
> > crocodylian hatching from a soft-shelled egg.
> > Attenborough even talked in terms of the mother
> > helping them hatch out of their leathery eggs.
> >
> > Also, as the croc mother was laying the eggs,
> they
> > did
> > seem to be fairly soft, though this was much
> > harder to
> > be certain of. They were dropped an inch or two
> > onto
> > each other without causing any damage or even
> > noise.
> >
> > I've repeatedly seen it claimed that all crocs
> lay
> > hard shelled eggs, and every croc egg I've seen
> > (on
> > TV) away from the nest was hard. Can someone
> > confirm
> > that they are soft when laid, harden up after
> that
> > and
> > then become soft again before hatching, and that
> > this
> > is what happens with all modern crocodylian
> eggs?



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