A square horn coral!? Answer to Freak of the Week #34


Goniophyllum pyramidale, a square horn coral!

So did I give you enough time to ponder this unusual specimen from the Orton Geological Museum!? Maybe I should change this series to Freak of the Month! It’s been a busy time here but hopefully we’ll be able to post on a more regular basis soon. But congrats to Dorene who came the closest, she guessed that it might be a coral. It is indeed a square horn coral, Goniophyllum pyramidale. In life this animal had four triangular flaps, known as opercular valves, which would have covered the opening. This specimen is from the Silurian Period, approximately 430 million years old, and was collected in Gotland, Sweden.

Zaphrentis – photo by James St. John

In Ohio we’re used to seeing the common horn corals, which were found throughout most of the Paleozoic Era. The photo is a of solitary rugose coral (“horn coral”), Zaphrentis, from Indiana but is also found in Ohio. You’ll notice that the ridges inside the coral, known as septa, are similar between the European square coral and our commom horn coral; a clue that the unusually shaped specimen is probably a coral!

Thanks to Dale Gnidovec, Curator of the Orton Geological Museum, for the idea and for providing the information about the specimen.

Posted April 15, 2015
Topics: Natural History
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