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Thread: Fossils

  1. #1 Fossils 
    Forum Sophomore
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    Sep 2005
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    1) Differentiate precisely between a chemically altered (petrified) fossil and a cast fossil.
    A petrified fossil and a cast fossil seem to be the same to me. They are both mineral replica of the original organism...






    2) For the above chart of index fossils, I don't know which is the name of the fossil and what does the other represent? For example, the second one, Pecten jeffersonius, MOLLUSCA, Pelecypoda, scallop, which is the name of the fossil and what does each of the above terms represent? For the "Tertiary-Quaternary" at the end, is it saying that this is a index fossil of both the Tertiary and Quaternary Periods?

    3) For the first one (Oleneothyris harlani), unlike the other three, there is nothing written after BRACHIOPODA, why?

    I didn't take biology so this stuff is a pain for me! Can someone explain? I would really appreciate!


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  3. #2  
    Universal Mind John Galt's Avatar
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    In the case of a petrified fossil portions of the original fossil are replaced by minerals. One is left with a solid form, replicating the three dimensional shape of the original.
    With a cast the impression made by the fossil on the enclosing sediments is preserved through mineralisation. No part of the original organism is systematically mineralised. The fossil is a two dimensional surface.

    The species name is the first item listed e.g.Phacops sana.
    The words in capitals are the phylum to which they belong. e.g. Brachiopoda.

    The words following the phylum is just an optional subdivision.


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