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Tiesta

Corals of the Twin Cities

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Tiesta

To me, fossil corals in the Twin Cities are rather rare and it can be tough to look for one. Bryzoans are vastly the most common colonial animal in the fossil layers of the Twin Cities with my guess easily 99% with one percent or less of corals and grapholites. First we are going to start with till. Yes, the till can once in a while yield fossils of corals from further north from other Ordovician rock beds. They are tough and can weather better than some other fossils. Here's one I found in my backyard. Even thou it's bluish grey it is much harder and thicker than the bedrocks in the Twin Cities. Just noticed a second coral species on this rock that was harder to see.

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Darktooth

Where's the pic?

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Tiesta

I have to alternate between my iPad which is easier to type and my phone which have better quality pictures so sorry.

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Tiesta

From my perception horn corals are the most common coral species in the twin cities with a encrust species of coral second with the rest much rarer. With horn corals I found one in platteville not sure if it's a different species or not. Funny enough to me they can be mistook for cephalopods from the same beds.

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Tiesta

The next species of horn coral are the most common of horn coral I have seen so far. Can be mistook for bryzoan. I call it calfs horn coral because of its small size and smooth sides. Mostly decorah but also decent numbers in galena. Lambeophyllum profundum.

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Tiesta

The last species of horn coral species I only just found last fall and is uncommon. Clearly it's a Lambeophyllum species but unlike calfs horn it have blunt base and abrupt widen to a big size. I have nickname it wide mouth horn coral. Kinda unusual for a horn coral, I feel like it is more like an armored sea anemone, complete with stingers since it appear unable to retreat into its hole.

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Tiesta

Now on to encrust corals. The most numerous I have found is Lichenaria type which I called wasps nest coral. I usually find it on bryzoan pieces.

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Tiesta

On to colonial corals. They're the rarest and I have found singles of two species so far maybe more. One is very worn and could had come from till that had fallen down into lilydale and is hard to picture. The other one is the biggest coral I have found so far in lilydale I found it last fall and found the name in Cincinnati fossils an elementary guide to the Ordovician rocks and fossils of the Cincinnati, Ohio, region by R.A Davis. It look like it came from galena formation, called Tetradium sp. At first it look like crystals or even petrified wood, this extinct genus of coral are bizarre. Tightly grouped and have tiny polyps. The holes have four sides compare to the hexagon of many living species roughly squared or short rectangular so not neatly organized. Hard to believe such tiny corals can build up so big.

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