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Re: Dinosaur diversity



Nathan Myhrvold wrote:
> I was imprecise.  "Landlocked" is not really the requirement - indeed it
> would be something of a problem because you'd like to have fish in the
> lake too, otherwise there is nothing for the hypothetical aquatic
> mammals or dinosaurs to eat.   Some landlocked lakes have fish - many do
> not.

The interesting thing about the fish in lakes Tanzanika and Melwabi
(sorry about the lousy spelling) is though they are rift-formed lakes,
it's been shown that the HUGE variety of cichlids in these lakes alone
are no older than 800,000 years as species and that these are unique to
these lakes.  Also in these lakes are fish with many primitive
characteristics similar to lungfish (including lungfish) like bichers
(secondary set of lungs), butterfly fish, and other oddities.  So
land-locked lakes would seem to also be hotbeds of evolution.....

> All it really has to be be for the argument is "mosasaur-free".  A lake
> connected to the ocean by a river with waterfalls etc. which would
> prevent large aquatic reptiles from entering is a sufficient condition.

Ever see an alligator gar?  How about a really large sturgeon or pike? 
How about a paddle fish? The fish are as likely to take the large
aquatic predator niche as any silly ol' lizard.

> 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).  Why does it seem
> harder to get mammals to these places than everything else?   Why didn't
> either mammals or dinosaurs compete in marine environments?

wasn't most of Europe isolated islands and large lagoons during at least
the Jurassic?
I'm thinking of the Solnhoffen stuff primarily.

-- 
           Betty Cunningham  
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