And the state fossil of Minnesota is...

...nothing. Despite the map on "List of U.S. state fossils" [note, 2018/2/22: this has since been fixed], Minnesota does not have an official state fossil. There was a push to draft the giant beaver into this position, but the rodent fell short. The immediate political reason for its failure can be grasped from its scientific name: Castoroides ohioensis. Should the state fossil of Minnesota refer to another state? Certainly not!

Algae and not-algae

The last of the fossils to be covered to complete the Upper Ordovician Twin Cities set (barring some microfossils and real rarities) are a nebulous group of oft-times enigmatic organisms that either are algae, or have been classified as algae. "Algae" is a much more problematic a term than you might suspect. To put it simply, "algae" is more of a state of mind than a formal classification. At its broadest, "algae" covers basically anything that does photosynthesis and doesn't have the obvious distinct tissues of derived plants, like leaves and roots. This would include anything from diverse microbes to seaweeds. While this has some utility for back-of-the-envelope things, it is not the most useful term for serious classification. It should not be surprising that untold numbers of fossils have been been classified as algae, and that many of these "algae" belong to disparate groups, some of which still have unsettled classifications. About a half-dozen taxa from the Platteville, Decorah, and basal Cummingsville formations have fallen into the "algae" bin at one time or another. They include the following: