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Hi, everyone. I found this rock yesterday in Illinois. I was thinking it could be petrified wood. I had my doubts, so posted elsewhere looking for an ID and received a response of “some type of coral”. Later in the night, while looking up fossil corals, I happened upon the word “Chaetetes“. When I looked it up, a few pictures seem like a close match…maybe exact? I’m wondering what the experienced think about it. Thank you.

On one of the last days of 2021, my daughter and I went for a walk to my favorite place. This is a forest stream in the Troparevo Park. I have been interested in these places for several years from the point of view of observing an island of nature within a large metropolis. I observe many species of birds, insects and plants there. There are species listed in the Red Book of Moscow. Here is an example of a very rare insect "Conocephalus dorsalis" - https://www.inaturalist.org/observations/93245215, which I observed in August. I hope that my observation will be taken into account when compiling a new edition of the Red Book of Moscow in 2022. Let's go back to the fossils. In the stream there are fragmentary Paleozoic rocks (carboniferous) brought here by a glacier from the north of Russia. Below are the photos taken on the day of the walk (18.12.21): Chaetetes sponge photo: I hope that I will soe a more complete account of my modest finds in this place.

Here are two interesting Pennsylvanian fossils that I bought at the Flagg Gem and Mineral Show in Mesa, Arizona (~4.5 inches wide) from the Apex Mine near St. George, Utah hosted in the Callville Limestone. A Chatetes sp. sponge is coated in azurite and malachite. Syringopora sp. coral molds are in goethite with significant germanium and gallium values. The goethite replaced the limestone. See this USGS article about the mine: https://pubs.usgs.gov/bul/1577/report.pdf

I've always been fascinated with the chaetetid sponge reefs that dominate the limestone beds of the Pennsylvanian Marmaton Group. Since these strata outcrop thirty to fifty miles east of the Kansas City metro, I don't have many opportunities to find them. This weekend, we drove out to a family event in southeast Missouri. I took the opportunity to check out a road cut in the Pawnee Formation near Holden, Missouri that I had read about in a publication. The chaetetids are present in the Coal City Limestone member of the Pawnee. At the expected spot, I encountered the black Anna Shale and a thick limestone that could be the Coal City: The limestone was basically barren. When I stepped back, I noticed that there are actually two limestones in the cut: Yeah, now I remember. The lower ledge is the Myrick Station Limestone. The one I'm looking for is on top. Up close, it appears to be an impenetrable wall. No fossils could be seen on the weathered joint surface or in the rubble: