The bottom thing with the long lines is a horn coral (singular rugosa) and it is an angled cross section which is actually really cool because you can see the septa (the lines) and the interior of the skeleton! The pitted stuff above is probably going to some sort of other coral but it is too blurry for me to actually be able to tell. Nice horn coral!

Hi there, @chad-bruce do you have a more specific location of where this was found? I believe that the age can (hesitantly) be identified as Ordovician. If you could also fill in the dimensions box that helps make it a research-grade specimen! @samantha-ocon may be able to help identify your possible trilobite!

Hi, @mackenzie-ross-2 and @Chad-Bruce! I think photos of other sides of the fossil would be useful here, but I do see how this could be a trilobite pygidum (butt).

Hi @mackenzie-ross-2 and @samantha-ocon, Thanks for getting back to me about the fossil. I unfortunately don’t have any more specifics on where it was found. I found it probably 15 years ago when I was a kid, and just kept it for all this time. Also, do you want dimensions of the rock or the specimen in the rock?

@chad-bruce That’s alright! Thanks for getting back to us! Dimensions of the specimen, if possible!

It doesn’t look like a trilobite

On the side

Most likely some kind of mark from an ancient marine creature or a different kind of marine species

Hi @mackenzie-ross-2, I added the dimensions of the specimen, and I measured from the edge of the indentation. As for the location, it’s entirely possible that it’s originally from northern lower Michigan and was brought to newberry from a quarry.

it looks so much like a shoe imprint, even though it isn’t. my theory is that it’s a shed trilobite carapace imprint of the inside of the shell

Michigan represent!

That looks like another Spirifer fossil- Spirifer connicus. Looks like a mold that was filled with sediment and recrystallization has occurred on the margins. The curved line could be a shell fragment that is on edge.

@jbauer any ideas on this Michigan fossil?

This looks like a bryozoan

Thanks @sadie-mills. I agree with @paul-mclain it looks to be a section through a bryozoan. It could be a small coral fragment too, hard to tell since it’s fragmentary and worn!

This could be an internal cast of a Brachiopod. Shell fills with sediment and dissolves away leaving behind a replica of the inside of the critter rather than the outside. These internal casts are called steinkerns.