Monday, February 14, 2011

Cayugaea from the Silica Shale

Cayugaea is an interesting rugose coral that I've struggled to ID since I first found two specimens on the dumps in Sylvania. It's odd to me because the shape of the body starts narrow and stays that way until suddenly widening out whereas most rugose corals have a smooth, constant growth pattern with the body widening as the animal grows.

When you look at the calyx (the cup shaped area at the top of the coral where the animal lived) is has convex, bubble like tabellae lining the interior. These structures are similar to Cystiphylloides which is also found in the Silica Shale but has a more traditional gradual widening growth pattern.

A view of a cross section through the "neck" area shows the same tabellae lined the interior of the coral.

Thanks to the 1975 book by Robert V. Kesling & Ruth B. Chilman: Strata and Megafossils of the Middle Devonian Silica Formation: Museum of Paleontology, Papers on Paleontology, No. 8, pg. 51, pl. 3, 6. I am confident that the above specimen is Cayugaea intermittens.

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