Yes, fossil - crinoid ossicles.
There is a slight anomaly in that they look like moulds, yet they seem to have the vacant central canal as if they were the originals. I think that they may be the acutal fossils, just partly eroded around the edges, though I'm not sure why that might happen.
Note that the specimen also has modern borings, mainly top-left and middle-right. They account for the extra two or three holes near the middle of the upper ossicle.
Thanks so much, Mike.
Can you possibly tell me the age of this fossil? Is it Devonian?
Also, sorry to be a bother, but what is a 'modern boring'?
Thanks again for the speedy reply!
I can give you an idea of the age, if you can tell in more detail where you found it.
There are many modern organisms that make borings into substrates. Shipworm (Teredo) is a bivalve that bores into wood. Other bivalves, various worms, etc. bore into rock; some bore into sea shells. The 'boring' may be accomplished by various methods: some bivalves have rasping exteriors to their shells, other organisms dissolve rock. Seaweeds and sea lilies have holdfasts, which can also make depressed marks on their anchoring rocks. (Other creatures use natural adhesive to hold themselves in place, eg. barnacles and limpets.)
The same sorts of creatures that make borings today, used to make them in the geological past. So, we also find fossil borings. Because these are traces made by organisms (rather than the organisms themselves), they come under the broad heading of trace fossils (ichnology). Simple, unbranched, cylindrical borings (like those in your specimen) can be called Trypanites.
With trace fossils, it is important to understand that the genus names (such as Trypanites) don't generally refer to particular organisms. That's because in most cases, we can't be sure what creature made the trace, and it is perfectly possible for multiple creatures to create trace fossils that are indistinguishable from each other.
Trace fossils are fascinating.
Wow, thanks so much for the detailed info. I can admit I am very new to all of this, so some of what you've said goes a bit over my head and will require digestion
But, it sounds like there are TWO different types of markings from organisms: the possible fossil or mould, and the borings. Is that right?
I found the fossil in South Devon, in a tide pool at very low tide, in Thurlestone. If it helps I can attach a few photos of the tide pool. What other info can I provide?
Thank you, I am finding this fascinating!
Most of the rocks around Thurlestone are (yes) Devonian.
They are mostly in the Meadfoot Group (a stratigraphic part of the Devonian in SW England). They comprise slate, siltstone and sandstone, formed from mud, silt, sand and gravel laid down in shallow seas about 398-411 million years ago. (There is a small exposure of Beeson Grits Formation on that part of the coast; that is of similar age. But chances are, your specimen is from the Meadfoot Group.)
Yes, there are two distinct types of organic markings: fossil sea lily stem fragments and modern borings.
New and strange info is best digested slowly - otherwise there's a risk of indigestion!