Re: Crocs, Amphibians, Small dinosaurs and the Impact theory.

[Roberto Takata <rmtakata@gmail.com>]

Well, we have to take into the account the facts.

Fact one, there is no known fossil record of dinosaur species - except
aves - after 65 millions years ago.
Fact two, there is no known fossil record of many other groups after
65 millions years ago.
Fact three, there is a iridium-rich layer in many sites over the world
in rocks about 65 millions years old.
Fact four, there is a great impact crater remains in the Chicxulub,
Yucatan, Mexico Gulf, dated around 65 millions years ago.

With a great probability a bolide colide with the Earth around 65
millions years ago. Was it  the cause or not of the K-T mass
extinction, frogs and crocodiles have to manage to survive that
impact. So the frog and crocodiles surviving could not be used to deny
the bolide impact as the K-T mass extinction - or at least a long
argument must be made.

But, yes, we have to answer: why dinos died, and frog and crocs
survived? Maybe they are not so sensitive to climatic change in a
medium term. Some frogs species manage to resist freezing.

A interesting challenge to life was what must happened to the sex
ratio in species with temperature dependent sex determination - TSD -
like crocs. (If there was a good fossil record across that K-T
transition to species with TSD and known sexual dimorphism it could be
very revealing.)

[]s,

Roberto Takata

2005/11/8, Mike Lima <taradosgon@yahoo.com>:
> I've heard Bakker use the fact that amphibians are the
> most sensitive to climate change to argue against the
> Impact Theory and in favor of disease. What about in
> the Permian-Triassic extinction event? Does he favor
> disease there too?
>
> Moving to the other side. I admit that frogs are very
> sensitive animals. So if the Permian-Triassic
> extinction was caused by a massive drought and
> increasing temperature and the K-T extinction by a
> comet impact how did the amphibians survive? In WWM
> the labyrinthodont "cocooned" itself (in what
> exactly?) in an attempt to wait out the drought. Do
> amphibians do this?
>
> The same question for Crocodiles as well. If they
> cannot tolerate colder climates (which is why
> labyrinthodonts survived for extended periods in
> colder areas?) how can they tolerate the sun being
> blocked out?
>
> Lastly, in reference to the impact theory, after going
> to
>
> http://www.usatoday.com/news/science/aaas/2001-11-24-dinosaur-extinction.htm
>
> it says that the since only fern species were dominant
> after the K-T boundary all the herbivorous dinosaurs
> including the small "polar dinosaurs" died out. How is
> this evidence as to why the "polar dinosaurs" died out
> if they were more adapted to the cold and (as far as I
> know) weren't ferns an adequate food source for the
> small herbivores?