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Re: ichthyosaur naris question

It probably has to do with the way each group swims. Whales swim with a
vertical motion while ichthyosaurs swim with a horizontal motion. Because of
this when whales go to the surface to breath, their dosal surface brakes
first. Ichthyosaurs however, probably rolled at the surface so as to
maintain their momentum while swimming. Perhaps basal ichthyosaurs swam slow
and methodically like turtles, and like them just lifted their heads out of
the water when needing a breath.


----- Original Message ----- 
From: "David Peters" <davidrpeters@earthlink.net>
To: "dinosaur list" <dinosaur@usc.edu>
Sent: Tuesday, January 11, 2005 5:38 AM
Subject: ichthyosaur naris question

> On basal ichthyosaurs the nares are dorsally situated, but on derived
> forms the nares split apart and are laterally oriented, rather than
> moving on up the forehead, as in whales. Does anyone know what's going
> on here?
> David Peters
> St. Louis