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Identification Help Requested ( Large Mississippian Bryozoa?)


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Hi everyone,


These unidentified specimens were collected in Union County, Illinois. It's from Mississippian strata, likely the Ste. Genevieve Limestone or St. Louis Limestone. I haven't been able to track down a proper map of this quadrangle yet.


The smaller specimens resemble mound bryozoa like Prasopora and the cups of all of them display concentric layers like related bryozoans. There aren't any pores visible so I've been thinking about bisecting one of the smaller specimens to see if any radiating zooecia are visible.


What does everyone else think? Does anyone have any idea on what they are?





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There were more obvious fluid vents in the site where these were collected so that seems very likely now that I think about it, especially given the variation and lack of any pore/cell structure. Very much appreciated.


In that case the concentric layers would represent infill structures of depositional events. While searching for variations in fluid vents I came across this interesting website on fluid venting systems. It's a good read for anyone wanting to learn more about these.

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