RE: mosasaur babies/no marine dinos

[Ronald Orenstein <ornstn@rogers.com>]

At 09:13 PM 02/01/02 -0500, John Bois wrote:
> This falsifies the equatorial barrier hypothesis.

Not at all, as has been pointed out - the equator is not an actual barrier, 
of course!  More to the point might be the observation that the equatorial 
range of the Galapagos Penguin is still separated by a vast gap from the 
most southerly of the Pacific Auks, Craveri's Murrelet of the Gulf of 
California.  Apparently the waters in between are not ideal habitat for 
either group.  In the Atlantic, the gap between the southernmost alcid and 
the northernmost penguin is far greater; even non-breeding penguins rarely 
get farther north than southern Brazil.

But not a polar continental land mass free of mammals.  A relationship
> exists between the area of a land mass and the diversity of its
> species.  Penguins are diverse, auks not--was this the case always?  Are
> you suggesting that auks were as specialized/derived as penguins?

Actually, I would disagree about the diversity comment.  Considering living 
(or, in the case of the Great Auk, historically extinct) species only, 
there are 17 species of penguins in six genera and 24 species of auks in 12 
genera, so auks are actually more diverse than penguins.

Secondly, only three of the 17 species of penguins nest on "a polar 
continental land mass free of mammals", and of these one, the Chinstrap, is 
only a local breeder on the Palmer Peninsula.  This is actually fewer than 
the four species that nest on continental land masses with land-based 
mammalian predators - the Magellanic and Humboldt in South America, the 
Black-footed in Africa and the Blue in Australia (not to mention introduced 
predators on new Zealand, where three species nest on the main islands, and 
the species nesting on the Falklands, which had an endemic species of canid 
until it was exterminated in the 19th century).


--
Ronald I. Orenstein                           Phone: (905) 820-7886
International Wildlife Coalition              Fax/Modem: (905) 569-0116
1825 Shady Creek Court
Mississauga, Ontario, Canada L5L 3W2          mailto:ornstn@rogers.com