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Re: Dinosaur diversity



At 08:56 PM 15/07/97 -0700, Jonathon Woolf wrote:
>Nathan Myhrvold wrote:
>> 
>> Part of the reason to speculate about such systems is that they might
>> illustrate .  As an example, most isolated island systems are mammal
>> free, so giant reptiles and birds fill the niches.  There are even
>> islands with giant insects (St. Helena, New Zealand).  

Where 'giant' means an insect in the large mouse, small rat size range 
which fills approximately the mouse niche.  The Moas were indeed 
very large birds and we also had a species of giant ghecko (I can't 
remember the exact size, only one specimen is known - from a 
French collection - the specimen was unlabelled and identified as 
a NZ species by features only found in other NZ gheckos - a creature 
fitting its description was noted in Maori legends).  We also had 
the worlds largest Eagle.

>>Why does it seem
>> harder to get mammals to these places than everything else?   

New Zealand split from Gondwana before there were any mammals here.  
For this reason we have only two species of indigenous 'terrestrial' 
mammal, both of which are bats - and plenty of aquatic mammals.

>Small rodents like rats do seem to turn up
>fairly often, but then rats are generally vegetarian and have low food
>requirements because of their size, so they could make it on a raft that
>served as both ship and sustenance.  

The method by which the kiore, or polynesian rat, reached these shores 
is a slight twist on this.  It was taken on board canoes deliberately 
as sustenance for the Maori navigators.




---
Derek Tearne.   --   derek@iprolink.co.nz   --    http://url.co.nz/   --   
Some of the more environmentally aware dinosaurs were worried about the     
consequences of an accident with the new Iridium enriched fusion reactor.   
"If it goes off only the cockroaches and mammals will survive..." they said.