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Re: The Biggest Dinosaurs

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
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
extinction of large animals over many many years.  In addition, did the
elephants on this island evolve smaller or evolve from a smaller ancestor?
How do we know how fast they may have evolve a smaller size?
   The fact that elephants (and relatives) died off in/around North
recently, doesn?t mean that they can not live in other pockets around
the world or that they could not live there today if they were
I think the trend still stands that elephants are the last remnants of a
branch of
large mammals that have been going extinct due to habitat isolation.

        Mark Shelly