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.
Sorry it's a bad picture but i can assure you the large fragment it is an ammonite and not a mammoth tooth. It is much clearer when you actually see it. In answer to your question though it was dredged off either the east or west coast.
Hi enthusiasts and nhm experts,
Can anyone provide any possible explanations as to how these fossils may have formed within one another etc?
I'm really interested to know more about this "phenomenon"!
any information would be greatly appreciated,
I have attached two other photos which hopefully show a bit clearer that it is not a mammoth tooth.
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.
Thank you for your quick and helpful response, I really appreciate it.
It was difficult to take a photo that clearly showed the smaller spiral sticking out of the larger one in any detail, so I understand the difficulty in commenting from the images provided.
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.
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'.
Thanks for your explanation. I hadn't realised it was common to find fossils within fossils, however the concept of them using empty shells as shelter makes a lot of sense!
Thank you also for your really interesting photos, they demonstrate it clearly.
A lower Jurassic upper Lias ammonite Dactylioceras tenuicostatum.
With at least one ammonite and two bivalves inside of its
Found on the Holderness coast.