Found this Crinoid on the Holderness coast a long time ago and was wondering if the crown was inside of the rock.
Don't know wether to have a go at prepping it because all of the arms seem to be going to the center after i removed some of the outer matrix.
...I suggest not!
If you work in from the other side, and if there is not much fossil, by the time you have prepped it, there won't be enough stone left to support it - it will be very likely to break.
Personally, I'd work from the side you started, and see (test first) if you can get any differential action with acids applied to both fossil and matrix, and/or paint acid carefully only on the matrix to weaken it, and/or abrade the matrix away with a dental drill.
Interesting - I am having trouble viewing the details of the arms, so cannot be absolutely certain from the photograph there may be another possibility. Perhaps a more detailed photograph might help - however, it seems very likely you have a crinoid crown. Crinoids are found in similar orientation from two possible forms:
1. Crinoids are often found with the cup in an upturned position, with arms splayed out, branching and dividing. If your specimen is a crinoid crown (head) then is is upturned and you are looking at a weathered, upturned cup - the stem would have broken off. There would be no point in trying to prepare it out further. Can you see any details on the large mass in the middle as this is the cup (Calyx or theca), if you can - we might be able to identify it further from the features of the cup and the branching arms (brachials). A clearer photo, with higher magnification on the arm in clear focus on the arms?
Other possibilities are ....
2. Crinoid attachment structures or holdfasts are found and look like miniature tree-roots.Crinoids anchor or attach themselves to the seafloor, bryozoans or substrate by a number of different mechanisms such as:
You can find more about the different structures of crinoid attachments structurs on page 51 of the online paper I wrote, published in Scripta Geologica 136 which you can find by copying the title below in google search.
Towards a systematic standard approach to describing fossil crinoids, illustrated by the redescription of a Scottish Silurian Pisocrinus de Koninck -
I hope this has been interesting to you.
Happy New Year!
Good to here from you, I cannot doubt what conclusions you have come to over this specimen because I know very little of fossils from the chalk.
If we find one on the Holderness it is interesting and usually get's put in my shed for a closer look when i come across it again.
I will post some more clearer images of the specimen in the daylite, unfortunately christmas and new year is still on the go and we are very bussey, usually the only time I have at the minute comes after 9pm !
I have another specimen that I recently posted an image of that I would say was a certain 'holdfast', I will start a new post with images of this Crinoid.
Hello again Fiona.
Thank you for the direction towards the paper you wrote about different structures of crinoid attachments, I will follow it up.
When we find something different on the Holderness coast after many years of collecting from the area it usually turns out to be very interesting, but if I only had time.