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5571 Views 9 Replies Last post: Jun 7, 2013 11:18 AM by Fiona - Museum ID team RSS
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Jun 4, 2013 8:38 AM

A fossil Jellyfish?

I have recently moved to Herefordshire and found this "fossil" in a dry stone wall in my garden.


After some research via the web I think it might be a Stromatolite or a Jellyfish or ?


Regards John



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    Jun 5, 2013 11:30 AM (in response to john451)
    Re: A fossil Jellyfish?

    Hi John -

    Jellyfish are rarely preserved due to the fact their bodies are made up of soft tissue that breaks down quickly at or soon after the time of death. The fossil jellyfish I have seen have clear circular outline. If we consider modern jellyfish on beaches, the tentacles would shrivel first and are more likely to be hidden or tucked under the 'bell-shape'. The shape of the rock suggests some sort of concretion with early diagenetic changes [please see definition below]. The features that look like tentacles are probably due to some sort of percolation filtering through the sediment.


    Diagenesis = changes to  sediment after rock formation at temperatures and pressures less than that required for the formation of metamorphic rocks or melting [adapted from Wikipedia].


    Concretions come in various shapes and forms, however, I am not familiar with this particular one. Perhaps you should take it to a natural history museum in Herefordshire as they may have something similar in their collections and can advise you further.

    I hope this has helped a little - sorry I cannot be more helpful.

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      Re: A fossil Jellyfish?



      Thanks for your views.

      I confess I was waiting to see what anybody else thought before posting myself.


      I think there is a concretionary factor, but I can't help feeling the object in the middle (concretionary nucleus) is in fact a fossil. I am mindful of discoidal objects in the Precambrian faunas not far away (Charnwood Forest in Leicestershire & The Long Mynd in Shropshire, and some sites in Wales).


      To quote from

      "Reviewing the Ediacaran fossils of the Long Mynd, Shropshire"

      by Alexander G. Liu1, 2011


      "The biogenicity of various other discoidal

      bumps and pits on numerous Longmyndian

      bedding planes has been debated for many years."



      A biogenic interpretation for Longmyndian

      discoidal features is therefore preferred, and the

      challenge is now to determine exactly what sort of

      organisms are being preserved. Callow et al.

      (2011) consider Salter’s “A. didymus” as most

      likely to represent structures related to microbial

      activity (cf. MISS; Noffke et al., 2001), while algal

      or microbial vesicle affinities have been explored

      for Beltanelliformis (summarised in McIlroy et al.,

      2005). Intrites has been compared to protistan

      organisms, while Medusinites aff. asteroides has

      variously been discussed as a trace fossil (McIlroy

      et al., 2005) and a polyp (Narbonne and Aitken,

      1990). With so few distinguishing morphological

      characteristics, elucidating the precise biological

      affinities of small discoidal impressions will

      continue to be difficult until we gain a better

      understanding of both modern biology, and the

      original depositional environments of these




      Llangynog in particular contains a

      fossil assemblage dominated by discoidal forms

      (Cope and Bevins, 1993), though those Welsh

      specimens constitute different taxa to those found

      on the Long Mynd.



      That paper is not a 5-minute read, but it is an interesting one (if you like such things!)


      In a similar vein,

      John Carney's


      What are we doing about them, and what are they?"


      That shows pictures of recent finds, including discoidal objects (different to Long Mynd ones).




      I am not saying your specimen is one of these Precambrian biogenic objects, but:

      - it is a possibility

      - it shows that such objects are subject to ongoing debate by current and experienced geologists.



      There's a good chance other stones in the same wall(s) came from the same source. I wonder if any of them contain more such objects and/or other fossils (which might help associate/dissociate them with the Precambiran faunas)...



      Please do take your specimen to the local natural history museum, and post back here about their comments!

      I think this is an interesting find, and certainly warrants following-up.




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        Jun 5, 2013 2:55 PM (in response to MikeHardman)
        Re: A fossil Jellyfish?

        Hi Mike,

        Yes, it is tricky, especially as the rocks are in a wall and not in situ. Possibly worth exploring, 3D fossils are known from Herefordshire, but these are usually Silurian. This is very specialised, a key researcher in this field is Mark Sutton UCL :

        David Riley and others from University of Leicester:

        "We are dealing with three dimensional fossils preserved within a volcanic ash - think of it as a 425 million year old Pompeii."


        Hope this provides a little more detail for you.


        All best wishes,


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          Jun 6, 2013 10:52 AM (in response to john451)
          Re: A fossil Jellyfish?



          Interesting further photos, thanks. It has more 3D relief than I had envisaged.


          So we do have a (loose) association with certain distinct macrofossils, which moves us away from a Precambrian fauna, statistically at any rate. Jellyfish, or jellyfish resting trace is still a possibility, IMO.


          Can you tell if any of those tentacly bits are composed of sediment or of vein-like minerals (which would probably be whitish, perhaps calcite).


          I'm more intrigued, and keen to hear what your local museum has to say.



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              Jun 6, 2013 4:15 PM (in response to john451)
              Re: A fossil Jellyfish?

              Curiouser and curiouser...


              The depth to the bobbly patch in the middle is interesting. If it had had zero depth, some folks might have argued it was a sole markings of some sort (like flute casts), but the depth pretty much precludes that.


              Strange that the rib thingys seem soft, yet are raised...

              If the rib thingys are mineralized (and that is not clear), that might hint towards concretionary structure (along the lines of septarian nodule). But the pattern of the ribs doesn't look right for that, and it looks a tad biogenic to me.



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                Jun 7, 2013 11:18 AM (in response to MikeHardman)
                Re: A fossil Jellyfish?

                Hi folks - now that we can see the 3D clearlly, tentatively, I think these features look like a trace fossil. You may find the following article of interest. Congratulations on an interesting find.


                Revista Geológica de Chile 35 (2): 307-319. July, 2008

                Depositional environment of Stelloglyphus llicoensis isp. nov.: a new radial trace fossil from the Neogene Ranquil Formation, south-central Chile

                Ambiente depositacional de Stelloglyphus llicoensis isp. nov.: una nueva traza fósil radial de la Formación Ranquil (Neógena), centro-sur de Chile

                Jacobus P. Le Roux1, Sven N. Nielsen2, Álvaro Henríquez1




                Stelloglyphus llicoensis isp. nov. is a large radial, discoidal to ellipsoidal trace fossil with a central shaft and single to bifurcating branches radiating from different levels. A 30 m thick measured section of the Ranquil Formation at Punta Litre contains an associated trace fossil assemblage including Zoophycos, Chondrites, Phycosiphon, Nereites missouriensis, Lockeiasiliquaria, Psammichnites(?), Parataenidium,Ophiomorpha, and Rhizocorallium, some of which reworked the Stelloglyphus traces. The sedimentology, together with micro- and macrofossils and the associated trace fossil assemblage, suggest that the succession was deposited in an outer continental shelf to slope environment in subtropical to tropical waters.


                I will show your image to a trace fossil specialist and see what they say.


                All the best,



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