Re: paleonet Jellies and Molluscs

[Carl Mehling <cosm@xxxxxxxx>]

Thanks so much! I was just curious because to my untrained eye, they 
looked identical.
Best,
Carl

At 01:08 PM 10/20/2006, you wrote:
> >And also, can anyone tell me how to distinguish, using only 
> shells, monoplacophorans from limpet-type gastropods?
>
>Some types of limpets have distinctive shell mineralogies or microstructure.
>
>If there's preservation of muscle scars, that's the best 
>indication.  Serial repetition of muscle scars is prvery probably a 
>monoplacophoran (though it's conceivable); a single asymmetric scar 
>is rather suggestive of a torted gastropod.  A single symmetric scar 
>is ambiguous.  Some limpet-shaped snails have distinctive muscle 
>scars such as a horseshoe shape.  If there's a protoconch, that 
>might help.  However, there are a lot of forms, especially in the 
>Paleozoic, where no specimens are known to preserve adequate detail 
>to definitively assign the taxon to a class.
>
>Limpets usually don't give much help from shell shape, but in some 
>taxa it's possible to compare what the water flow would be for a 
>torted or untorted animal and see which one works better.  I think 
>it was Paul Morris who did this for macluritids.
>
>Dr. David Campbell
>425 Scientific Collections
>Box 870345, University of Alabama
>Tuscaloosa AL 35487-0345
>"James gave the huffle of a snail in danger/ But no one
>heard him at all."-A. A. Milne

Carl Mehling
Fossil Amphibian, Reptile, and Bird Collections
Division of Paleontology
American Museum of Natural History
Central Park West @79th Street
New York, NY  10024
(212) 769-5849
Fax: (212) 769-5842
cosm@amnh.org