|Welcome to the Ordovician! Hope you like brachiopods!
|...or bryozoans and crinoids
No points for guessing which is which. The first photo shows natural molds and casts in the Platteville, while the second shows the well-shredded fossils of the thin limestone beds of the Decorah. Now try this one:
Despite the preservation, this piece is from the Platteville. Specifically, it comes from a bed about halfway up the Mifflin Member. Somehow this bed managed to escape the worst of the heartbreak of dolomitization, at least in a small area. Little glimpses like this show a richer picture of the Platteville fauna than we get from the natural molds and casts. (The tiny crinoid columnals are an interesting touch, as is the relative scarcity of bryozoans.)
|They're in there. It's a proper hash.
|The strophomenids might be a little smaller, too.
There are also snails, ostracodes, and some elongate triangular things. Some of these are probably small nautiloids, others might be hyoliths.
|The example near the center bottom of the photo is one I suspect is a hyolith.
There are a lot of subtleties to the rocks and faunal assemblages once you start looking!
(Also, having found a decent place to see the Glenwood up close, I've added a couple of photos to the old post.)