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1356 Views 9 Replies Last post: Jun 24, 2013 9:41 AM by eskinner RSS
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Jun 18, 2013 9:08 AM

ammonite in an ammonite

Hi,

 

I work for Tarmac Marine Dredging Ltd, an aggregate dredging company based in the UK. Our operations target sand and gravel deposits, often located in ancient river terraces and channels. 

 

One of the staff at our wharf in Bedhampton found this fragment of an ammonite (pictured below), which was dredged from a licence area located off the Isle of Wight, and noticed that it has another smaller ammonite within it!

 

I was wondering if anyone knew if this was a common occurrence or if it was quite unusual? 

 

Also is there anyway of determining the age of the ammonites based on what we have?

 

Any information would be greatly appreciated.

 

Thanks,

 

Ed

 

b3.jpg

b4.jpg

b5.jpgb12.jpg

b6.jpg

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    May 24, 2013 4:57 PM (in response to eskinner)
    Re: ammonite in an ammonite

    If you don't mind me asking, were exactly off the Island was this dredged. As this could determine whether or not it is an Ammonite. Because to me it looks like a Mammoth tooth.

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      Jun 18, 2013 9:46 AM (in response to eskinner)
      Re: ammonite in an ammonite

      Ed,

       

      I'm not entirely sure how to 'see' your specimen from the photos, but I think what you have is one of the involute ammonites. That means the shell wraps over its earlier (inner) parts as it grows. Sometimes the overlap can be slight; yours seems to show quite a deep overlap. This means that a fragment may happen to show what appears to be two shells, whereas in fact it is different parts of the same spiralling shell.

       

      Refs:

      - http://paleopolis.rediris.es/cg/CG2010_A08/images/TN_CG2010_A08_Fig_03.jpg

      (from http://paleopolis.rediris.es/cg/CG2010_A08/)

      - http://www.ukfossils.co.uk/guides/ammonites.html

       

      Mike

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          Jun 22, 2013 2:39 PM (in response to eskinner)
          Re: ammonite in an ammonite

          Hello Ed

          This type of ammonite preservation is not all that unusual, I do not know why maybe as they fought for survival they held onto the nearest thing they could get hold of.

          Maybe like a hermit crab the smaller ammonite looked for shelter in a larger shell, I do not know.

          Were I collect on the Holderness coast I have seen many Phylloceras sp partial ammonites with other Upper Lias Lower Jurassic ammonites

          and bivalves inside there livings chamber.

          I also have a Speeton (Cretacous) Polypachytes sp (ammonite) with a bivalve and sea urchin spines in it,s living chamber also found on the Holderness coast.

          I don't usuall collect partial specimens but the image below shows a Nautilus living chamber wit an Astioceras sp sat inside of it.

          The Asti is 7in across.

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            Jun 22, 2013 3:00 PM (in response to Tabfish)
            Re: ammonite in an ammonite

            Tabfish,

             

            Good post.

             

            I guess there may be a factor concerning particle sorting and flow dynamics during sedimentation - similar to how leaves or rubbish can accumulate in partciular street corners (also thereby increasing the chance of them getting intertwined). In the case of fossils with exposed cavities, the cavities could function as 'particular street corners'.

             

            Mike

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    Jun 23, 2013 11:12 AM (in response to eskinner)
    Re: ammonite in an ammonite

    Hi

    A lower Jurassic upper Lias ammonite Dactylioceras tenuicostatum.

    With at least one ammonite and two bivalves inside of its

    living chamber.

    Found on the Holderness coast.

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