Monday, August 3, 2020

Strombodes shumari coral from the Louisville Limestone

Below are two specimens that look similar but have some differences which could mean they are not the same species. I am working from partial pieces of larger corals so the best I have been able to ID these specimens is that they are Strombodes shumari from the Louisville Limestone.  I found them at a site near Louisville, KY a number of years ago and only got around to identifying them now.  I used the book by Erwin Charles Stumm; "Silurian and Devonian Corals of the Falls of the Ohio". to help ID and found a possible match on page 47, plate 22, fig. 1-8.

The preservation of the specimens is incomplete and so I can't find all the diagnostic details to truly confirm the ID. What makes me think I may be correct that these are Strombodes shumari is the pattern of rejuvenation of the calice. This is seen in the specimens as a reduction of the calice diameter via continuous growth over a short horizontal and vertical distance, only to renew vertical growth. The repeated growth pattern is the key to identify this species.

Specimen #1 - This and the next three pictures are the sides of the specimen as seen rotated 90 degrees from the prior picture.

Specimen #1 - A closer view of the calice where the rejuvenation surface is shown.

Specimen #2 - This and the next photo are of the side of the specimen and then turned 90 degrees. Note that this specimen only has one cycle of regrowth and has evidence of a more significant calcie size difference than the prior specimen. Perhaps this is a different genus or species, or perhaps similar evidence was not preserved as well in the prior specimen?

Specimen #2 - A closer view of the calice where the rejuvenation surface is shown.

A view of the partially preserved cross section of the calice.

I believe these specimens come from the Lousiville Limestone near Louisville, KY and are dated to the Silurian period (Homerian to Gorstian stage).

References: Stumm, E. C. (1964). Silurian and Devonian corals of the falls of the Ohio. New York: Geological Society of America.

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