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Re: dino extinction



Paul Willis wrote:

> A condralath (placental) mammal has been found in the Earliest Eocene
> deposits of Murgon, south eastern Queenland, strongly suggesting that
> placental mammals were present in Australia prior to separation from
> Anctartica at 38mya. Although the evidence is scarce, the plot appears alot
> more complicated than the old hypothesis of "Marsupials survived in
> Australia because placentals were not there to kick their evolutionary
> freckles".

You'll get no argument from me on that!  The presence of a condylarth
(_Tingamurra_) from the early Tertiary of Australia hints that the
dominance of marsupials on this continent came about not through
default (i.e. the absence of placentals), but because the marsupials
were competitively superior to placentals.

If this dominance also occurred in the Cretaceous throughout
Australasia, and for some unknown reason marsupials were more
susceptible to the K/T extinction than placentals, then it would
account for the absence of Tertiary mammals from New Zealand.

Or, as you say, mammals may never have been in NZ in the first place.

> >Almost certainly there were mammals there.  Just the wrong types of
> >mammals.
>
> Bah, humbug! this is supposition based on prejudice (exactly what is the
> right king of mammal?).

Beats me.  The K/T crash, like mass extinctions before and after,
was selective in its effect on different groups.  Some groups survived
with barely a hair (or feather) out of place; others disappeared
completely; others lay between these two extremes.  I'd go along with
Gould's idea that survival was a matter of "pot luck".  (Rewind the
tape of life, etc..)

Tim Williams

(Long live the marsupials!)