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Re: dino extinction?



On Tue, 6 Oct 1998 11:20:37 -0400 Allan Edels writes:
>  However, we don't know which if any, we don't  know which way the
selection might >have leaned (i.e. too warm => all males, too cool => all
females - or vice versa!)

It's even more complex than that.  Reptiles which do exhibit
temperature-based sex determination (TBSD) often show a varying selection
over a range of temperatures.  That is, of a given clutch of eggs, almost
all might be male at the lowest safe temperature range of incubation;
mixed male/female at mid range; almost all female a little higher; mixed
at slightly temperatures; and almost all male at the highest range of
safe incubation temperatures.  This can be a real headache when you're
trying to breed reptiles for the pet trade  (which I don't do, but
communicate with some people who do).

Also, TBSD sometimes depends on ambient temperatures at a certain stage
of development.  I highly suspect that this is true for all TBSD cases,
but have no data to prove this idea.  Sort of thing that can be written
up for a herpetological journal.  This stuff can be a real headache. 
Anyway, finding TBSD in dinosaurs is highly problematical, given these
factors.
-zenlizard

If one says a vacuum cleaner  "sucks",  does that mean it doesn't?

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