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Eliza
Hi,

I am wondering if someone could please help me identify this ammonite.

Found Black Ven, Charmouth, Lyme Regis.

Could someone please also identify the worm like structure across the fossil centre? Also the best way to clean this up.i have had a go as you can see!!

Many Thanks
20191002_222659.jpg  15706514365443018533678271419569.jpg  15706514716547643911965006816339.jpg  20191002_190929.jpg
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Barrow Museum
I think it is Arnioceras (?semicostatoides), a characteristic ammonite genus of the upper part of the Blue Lias Formation and the Black Ven Mudstone Member of the Charmouth Mudstone Formation.  A view of the venter (outer edge) and the inner whorls would be useful in confirming the classification.  If my species guess is correct, then it would have originated in a thin layer characterised by this species, within the Obtusum Zone.

The worm-like structures have indeed a worm origin - they are tubes secreted by a Serpulid worm, as its protective habitation structure.  the planktonic larval stage of these worms would have settled and started growing on a dead ammonite (or other hard shell or object) on the sea floor, as they preferred to attach to a hard substrate.  You can find living examples at the seashore today.
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Eliza
Thank you very much for your reply and information.

E x
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