Here is an odd-ball I found yesterday. Recently I found a new marine / brackish layer of dark gray shale. My first discovery was two root pieces, which I'll showcase at another time. I also found a tiny Glabrocingulum grayvillense (gastropod) there. This particular rock had a brachiopod on it, and I was getting a closer look. The matrix was soft enough to stab with my tweezers, so I was digging around the margins. This very tiny piece appeared that looked very interesting, and even more complex under the microscope.
It's very small. The further out photo shows it with a 1 cm scale.
I feel like this is a known marine animal shape, but It's not apparent to me.
You can see the opposite part of it on the top right of the following photo as well.