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795 Views 5 Replies Last post: Feb 8, 2013 12:21 PM by Fiona - Museum ID team RSS
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Feb 7, 2013 11:21 PM

Help identifying a fossil

I'm wondering if anyone might be able to identify this fossil-- it looks like a sea urchin to me and has 5 distinct indentations in a star pattern on the top and what looks like a mouth on the bottom.  I found it on a Beach near Mudeford on the south coast about 15 years ago and have always wondered what it is and how old it might be.

 

Thanks for looking!

 

Sarah

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    Feb 8, 2013 7:33 AM (in response to Sarah Shaw)
    Re: Help identifying a fossil

    Hi Sarah,

     

    You're right - it is a sea urchin, one of the irregular ones, preserved in flint by the looks of it.

    Sea urchins (and sand dollars) comprise the Echinoidea, within the Echinodermata.

    Irregular ones (loosely grouped into the 'Irregularia') are shaped that way because they burrow along the top of the sea floor, ingesting sediment, removing the food from it, and excreting the waste sediemnt behind them as they go. (The regular ones live on top of the sediment.)

    I cannot tell you which genus or species it belongs to (a local geology book would help, but I don't have one for the area).

     

    Your fossil probably eroded from the cliff, which is formed of the Boscombe Sand Formation, about 40 million years old (Palaeogene period).

     

    Ref:

    - irregular echinoid terminology - http://www.chalk.discoveringfossils.co.uk/irregular%20echinoid%20terminology.htm

    - another one similar to yours - http://www.ravencrystals.com/assets/images/echinoid196a.jpg

     

    Mike

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      Feb 8, 2013 9:50 AM (in response to MikeHardman)
      Re: Help identifying a fossil

      Hi Sarah - The test is heart-shaped so could belong in the Order Holasteroida or Order Spatangoida. It is not that inflated so in my opinion it is probably a Spatangoid echinoid. Please take a look at The Echinoid Directory (by Dr. Andrew Smith - expert in this area) and tell us what you think!

      http://www.nhm.ac.uk/research-curation/research/projects/echinoid-directory/taxa/taxon.jsp?id=244

       

      Have you made a label for your lovely specimen? If you would like a sheet of labels, please email me at IAS2@nhm.ac.uk

      All the best,

      Fiona

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          Feb 8, 2013 12:21 PM (in response to Sarah Shaw)
          Re: Help identifying a fossil

          Hi Sarah, I would think they would be at least 40  million years old and possibly older. They are known from the Lower Cretaceous (Valanginian) to Recent; worldwide. Although the geology of Mudeford is younger, as mike infers, it is likely your fossils have been reworked from older sediments (hence the slightly rounded features and weathering). They may be circa 100 million years old.
          All the best,
          Fiona

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