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Hi Everyone,

I went for a walk with my 4 year old son and went by a stream where I had found a fossil before (specimen 1 is the one on the left). We found a few more items and my son was asking me questions I did not have any answer for.

Any info on the below would be greatly appreciated and relayed to my 4yo who was excited to find these 'special rocks'.

(I also enjoyed looking at the larger one as its filled with little fossils - could I halve this to see whats inside?)

Thanks  Click image for larger version - Name: Fossils 1,2,3.jpg, Views: 51, Size: 264.79 KB Click image for larger version - Name: Fossil 4 (1 side).jpg, Views: 49, Size: 344.11 KB Click image for larger version - Name: Fossil 4 (other side).jpg, Views: 46, Size: 337.80 KB
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1 looks to be an oyster or bivalve
2 is a bivalve I think
3 is definitely an ammonite segment
4 is a rock with shells possibly brachiopods in it but I can’t see clearly
5 looks to be a rock with an oyster shell fragment and where a bivalve used to be.

Some of my IDs could be wrong so I would wait for someone else.

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Hello and welcome to the forum.
Firstly, please always give the best location details that you can as we need to be able to check the geology (hence age) of the rock(s) you are showing us. Also, photograph each specimen with a scale (a ruler is best).
However, with your finds, I am sure that they are from the Oxford clay (153 - 167 million years old).
The first photo shows (on the left) 1 valve of the bivalve Gryphaea but would need more photos to get to a species. In the middle is part of another type of bivalve but there isn't enough to give a genus. The right hand  find is a small part of an ammonite.
The middle photo is a chunk of hard clay or mudstone which as far as I can see (I enlarged the photo) with fragments of various shells in it.
The 3rd photo (reverse side of the same nodule)? has in addition a Gryphaea valve.
I hope this helps!
Colin Huller
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Brittle Star
As fragments on the surface it would not hurt to split it, maybe use a chisel to get a clean break. Inside will not be eroded. Let us know what you find. Getting a magnifying glass on the surface you may see the gastropod or it could be a cross section of a tiny ammonite showing the chambers.

 Never ask a star fish for directions
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Amazing - thanks for the replies and uploading tips. I’ll go through it with my son tomorrow (he is sure to be excited that these are older than me) and will definitely go out again to look for more with him. I’ll research the above as a starting point for getting some basic knowledge for more difficult questions. 

i will get a chisel and open it up and let you know what we find

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Barrow Museum
The first photo represents fossils typical of the Oxfordian Stage of the Upper Jurassic (around 150 million years old).  This would include the Oxford Clay and the  Ampthill Clay, which is a tad younger. The ammonite fragment looks to me like a Perisphinctes from the Ampthill Clay.  I suspect that your specimens were actually derived from the glacial drift, which covers a lot of Cambridgeshire. This glacial deposit was scraped up by ice during the "Anglian Glaciation" which occurred around 450,000 years ago, from the Jurassic formations which crop out to the north west and under the North Sea to the east.  When the ice sheets finally melted, all the rock debris, including the fossils, was dumped where it stood.  Further evidence of this lies in the nodule that you also found - the photo (Fossil 4, other side) shows just the edge of an ammonite which I am fairly sure is an Arnioceras - a genus that is found in the Lower Jurassic.  Nodules such as these occur in the glacial material all up the coast as far as Yorkshire, often with a multitude of these ammonites inside.  They may well have been dredged up from the seafloor by ice, but certainly originated a lot farther away than in Cambridgeshire.  If you have the opportunity sometime to visit the Sedgwick Museum in Cambridge, you will surely find someone in there who can comment on your finds.
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Dirty Pete
If you've got a mobile phone you might find this app helpful next time you're out. N H Museums interactive UK map / geology map and the fossils you can find.

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Evening all,

Managed to open the nodule - took a few taps with the chisel and opened up, but it means nothing to me I'm afraid. Once things reopen I will take to Sedgwick as suggested to satisfy my curiosity. I tried to take decent quality photos this time. 

On a side note - the ammonite segment surface comes away if scrapped with something sharp (thumbnail) with a very silty feel to it. I always assumed fossils would be harder? Feel free to correct my ignorance 🙂 I will try ready around the topic.

Thanks for all the info so far. Click image for larger version - Name: IMG_1138.jpg, Views: 25, Size: 287.44 KB Click image for larger version - Name: IMG_1139.jpg, Views: 25, Size: 293.78 KB
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Barrow Museum
I wrote a response 4 days ago to  "" which goes a long way to providing an answer to your question (it is a septarian nodule).  Suggest you read it first.  Big septarian nodules contract internally more than small ones so the network of secondary calcite-filled veins inside tends to be more prominent the larger the concretion.  Your nodule, being quite small, has only small shrinkage fissures and it is along these that it has broken - observe the thin crystalline infill and slight yellowish discolouration.  You might have had a better result trying to split it parallel to the original bedding (which would have been along its broadest axis) as shells and other objects destined to become fossils tend to lie flat on the sea floor.  Pity about that ammonite.  You probably have nothing to lose by cracking open the two pieces you have to find out if there are any more bits and pieces inside.  "Fossils" can be hard or soft or anything in between (even a hollow cast counts).  It depends upon what has happened to it after burial.  It is sometimes a difficult task to remove well-cemented matrix from a delicate shell or bone.  When you can, go back to the locality and I am sure you will discover lots more, now you have your eye trained.
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