Re: The Biggest Dinosaurs (slightly off topic)

[Dann Pigdon <dannj@alphalink.com.au>]

Mark Shelly wrote:
> 
> Re: The Biggest Dinosaurs
> 
> Christy Nadalin asked: >>> Does anyone have any thoughts about why
> dinosaurs in Patagonia were growing so large during the Cretaceous,
> while it seems that the trend was the opposite elsewhere in the world?>>>
> 
> Among my thoughts implicating habitat loss and regional isolation:
> >>  I can not help feeling that the plight of the elephants, mammoths, and
> mastodons is not similar.  Once their regional pockets they lived in were
> gone (due to expanding deserts, glacier advances, expanding grasslands,
> farming and shepherding man) these animals are/were doomed.  <<
> 
> To which  Betty Cunningham replied.
> >but this seems to ignore those island-dwelling dwarf elephants found
> near Southern California.  If they were in this kind of surroundings
> long enough to become dwarfed (genetically) then the population must
> have been viable for quite some time in just such a situation as you
> infer.  Why couldn't this have happened to sauropods?<
> 
>    I am not familiar with this elephant.  However, an isolated habitat
> that
> could not support a large elephant might support a smaller one.  If it is
> extinct now, it just supports the thought that isolated habitats result in
> the
> extinction of large animals over many many years.  In addition, did the
> elephants on this island evolve smaller or evolve from a smaller ancestor?

"Pygmy" mammoths are known from islands off northern Europe, and
have been dated to around 4,000 years ago or there abouts. They
assumedly evolved from much larger ancestors. Not only did they adapt
to island living, but also mamaged to outlast their larger cousins.
I beleive from memory that they were never very numerous, and that
all sorts of diseases are evident in the most recent remains.
-- 
____________________________________________________

        Dann Pigdon
        Melbourne, Australia
        http://www.geocities.com/capecanaveral/4459/

____________________________________________________