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Re: On the subject of mysterious absences...The Answer

I typed too soon. Here's part of a post on vrtpaleo from Christine Janis
on this topic. -- Dan

"Not a mystery as to why no marine reptile became a filter feeder. Check out 
this ref 

Collin, R. and C. M. Janis (1997). Morphological constraints on tetrapod 
feeding mechanisms. Why were there no suspension-feeding marine reptiles? In: 
J.M. Callaway and E.L.Nicholls, (eds), Ancient Marine Reptiles.  Academic 
Press, New York. Pp. 451-466.

  Briefly: if you want to filter feed without gills, you need to take in a 
large amount of water and then somehow stop it going down your gullet before 
you spit it out past filtering surfaces such as baleen . Only mammals can do 
this, as only they have seals that shut off the back of the throat (such as you 
use when you gargle) -- probably evolved in association with suckling." 

Jamie Stearns wrote:
> If I may weigh in on a related issue, I've noticed another thing that
> would seem to be missing from Mesozoic times.
> Today's marine mammals usually include a variety of small toothed
> forms along with filter-feeding varieties. Filter feeders actually
> tend to account for the largest animals in just about any oceanic
> environment you find today.
> Yet in the Mesozoic, even the biggest pliosaurs, mosasaurs,
> ichthyosaurs, etc. are still toothy. Where are all the "baleen
> kronosaurs" that ought to show up?
> -Jamie Stearns