I found this fossil at Cayton Bay near Scarborough last Sunday while walking the dogs.
It was half embedded in a large sandstone boulder that had fell from the cliff onto the beach.
When I first got it out the boulder it was round like a cricket ball. I took it home and soaked it in luke warm water but after about 1hour a couple of pieces had fallen off. To my amazement it was hollow inside. I've never seen anything like it before.
Any ideas of what it is and age please.
ooh - Tabfish will like this one...
It is a concretion which formed around an ammonite, which has since dissolved away completely, leaving only its impression as an external mould in the middle of the concretion.
I've never seen one like this before. Nice find.
The structure looks weird until you think of its counterpart.
That's a great way to start!
(BTW, Tabfish has lots of experience collecting and preparing British fossils. He's a regular here. I do hope he looks-in.)
Thank you Mike, not enough hours in a day at the moment.
What a very nice find! it's a negative/cast of a Cadoceras ammonite.
I have been very lucky to find two specimens over the years on the Holderness coast, one in a good condition and the other one not so good but I have a similar cast to yours from a Lower Jurassic - Middle Lias ammonite called a Pleuroceras, that I will try to take an image of for you to have a look at.
Once again a very nice find and fantastic images!
I hope it's ok as I have attached an image of similar ammonites to the one you found.