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644 Views 7 Replies Last post: Oct 30, 2013 11:57 AM by Polacanthus RSS
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Oct 12, 2013 4:24 PM

Coral or Bryozoan?

Hello,

I wanted to ask you how I could safely say whether I have found a fossil bryozoan or coral.

thank you for your help.

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    Oct 19, 2013 11:57 AM (in response to Polacanthus)
    Re: Coral or Bryozoan?

    Im not an expert but it is quite hard to explain the difference.  Corals sometimes have little circles inside, and bryozoans sometimes have little dots that are different in colour to the rest of the piece.  If you could send a picture I would probably be able to tell.

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    Oct 20, 2013 9:28 PM (in response to Polacanthus)
    Re: Coral or Bryozoan?

    Hi Polacanthus

    internet search bryozoan/coral and were you found your specimen, this should help you with the id.

    Also search for your local geological society.

     

    Tabfish

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      Oct 21, 2013 6:40 PM (in response to Tabfish)
      Re: Coral or Bryozoan?

      I think it's probably fossil coral.  Bryozoans usually have larger dots that are visible with the naked eye.

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        Oct 21, 2013 10:38 PM (in response to Dan)
        Re: Coral or Bryozoan?

        Polacanthus,

         

        It is a good and perfectly fair question.

        The answer, unfortunately, is complex.

         

        Factors to consider:

         

        1. As living organisms, there are many significant differences between corals and bryozoans.

        http://www.bio.umass.edu/biology/conn.river/corals.html

        But as fossils, many of those features are not available. Even if they were available, you would need a microscope to make use of them.

        Also, there is complication due to 'convergent evolution' - whereby different creatures evolving in the same niches come to look similar.

         

        2. Both groups of animal are quite varied in their appearance (shape, patterning, size, internal structure, etc.)

        That makes it difficult to use a general category of shape as an indicator of either coral or bryozoan.

         

        3. Some sources suggest the size of the 'holes' as a guide: holes sub-millimetre in size being bryozoan; holes a mm or greater being coral. That is a generalization; it might be enough to get you started, but you would have to be prepared to find yourself barking up the wrong tree - as there are exceptions.

         

        4. Both occur through a large part of the fossil record.

        So you can't really use geological age as a clue.

        (Although some sources state bryozoans date from Early Ordovician, others report them from the Cambrian)

        (Geological age may help if you have some features to go on. For instance, if you have a specimen that looks like a rugose coral but comes from Cambrian rocks, it is actually something else (see diagram here).)

         

        5. There are groups of animals other than corals and bryozoans that look similar, eg. stromatoporoids, sponges, calcareous algae.

        So it may not be possible to correctly ID a specimen as coral or bryozoan because it is not either of them!

         

        6. Other factors that I can't bring to mind just now.

         

         

        So - what to do?!

         

         

        Often, the best approach (with fossils) is to try to ID your specimen by matching its features to more-specific groups of animals. If you have a good specimen, you may be able to see septa and/or tabulae, which might enable you to make an ID as far as tabulate coral, for instance. Then, you'd try to confirm/refine that by reference to tabulate corals (or whatever) reported for your particular collection locality.

        If your specimen lacked suitable visible characteristics, that approach would not work.

        As always:

        - there is a chance you cannot ID a specimen (it may be intrinsically ambiguous)

        - there is a chance information (on the internet or otherwise) may be wrong, leading you to a false ID or confusion

         

         

        If you're really interested in this stuff, may I recommend studying palaeontology!

         

         

        Refs: 

        - http://en.wikipedia.org/wiki/Bryozoa

        - http://en.wikipedia.org/wiki/Anthozoa

         

         

        Mike

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          Oct 22, 2013 6:47 PM (in response to MikeHardman)
          Re: Coral or Bryozoan?

          image.jpgHere are just a few of the fossil corals/Bryozoa that I found in East mallorca.  It really is fun fossil hunting in east mallorca.  I have never gone fossil hunting in North, South or west mallorca, but I just know it's really good fun in the East!  When I said about the circles in the corals, there is an example there. The one that is slightly upwards and slightly to the leaft of that one with another stem growing out of the stem is a coral.

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