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Re: Bird and mammal K-T survival

Adam,
I was not saying that there is no value in discussing this subject further. On the contrary, I wouldn't respond to a thread I thought was a waste of time.
My point is that there was no single "magic bullet" of survival, and extinction by competition and/or egg predation are definitely not in my top list of reasons to explain what survived K-T and what did not. Whether certain crocs or birds survived by having buried their eggs in the right spots is certainly debatable, but once the bolide hit (the "magic bullet" of extinction), I believe that all the normal factors of competition and egg predation would have been dwarfed by the struggle to just survive the devastation.
Neornitheans may well have been out-competing enantiornitheans at the end of the Cretaceous, so much so that the latter had perhaps become relatively rare in Antarctica. However, I also believe that if the bolide had not hit the Earth, that we would still have enantiornitheans living in some areas to this very day, much as monotremes have done (or perhaps been even more successful like marsupials).
Egg predation and competition may have had their effects (including extinctions of species, genera, and maybe even whole families), but it seems to me that it was the mass extinction event (impact) that sealed the fate of ammonites, enantiornitheans, non-avian dinosaurs, and other major groups. ------Ken
P.S. And I also believe that there sometimes a misperception that certain surviving groups got through K-T "unscathed". Even neornitheans probably suffered near extinction, and most of the surviving mammal families may have just gotten through by the skin of their teeth.
******************************************** 
From: "Adam Britton" <abritton@wmi.com.au>
To: <kinman@hotmail.com>, <dinosaur@usc.edu>
Subject: Re: Bird and mammal K-T survival
Date: Sun, 26 Aug 2001 13:07:26 +0930

From: "Ken Kinman" <kinman@hotmail.com>
Sent: Sunday, August 26, 2001 2:58 AM

>      We've been through this neornithine K-T survival discussion before,
so
> why is anyone still scratching their head for possible solutions?

Are you so convinced that the commonly-held theories are entirely correct,
especially given the holes in our knowledge about this period?


>     (3) burying your eggs like a megapode, preferable in alkaline soil
> (which would neutralize acid rain).
>      The third option was probably that which saved many crocodiles (and
not
> minding the ingestion of dead animals would have helped as well).

I seriously doubt that would have been a significant factor for reptiles,
birds or crocs. Croc eggs incubate for between 60 and 100 days - hardly long
enough to cope with the apparent effects this event had upon the world's
biodiversity. Eggs are one of the most (if not the most) vulnerable life
stages that oviparous vertebrates have, and young juveniles are either tops
or a close second. When it comes to crocs, long-lived adults with low
metabolic requirements seem far more equipped to survive, regardless of
their environment or shelter. Adults may go for 30 to 40 years without
producing a single surviving egg, yet given the opportunity and changing
conditions this situation can be reversed. This isn't wild speculation - we
know modern crocs do this, and we know just how resilient they are to
population pressure imposed by environmental factors. Some species certainly
survived this period like they survive any period - they have inherent
biological and/or ecological mechanisms to cope with adverse conditions.
Even if the causal mechanism was short-lived, species had to endure
longer-term changes to their environment.


>       I just don't think it is such a big mystery.  The survivors of the
K-T
> catastrophe were lucky enough to be in the right parts of the world, in
the
> right niches, and being a generalist feeder certainly was another plus.

Whether we concur or not, I do not agree that there's no value in
re-examining what little evidence we have.

Adam Britton


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