Saturday, November 17, 2012

Ancyrocrinus anchor from 18 Mile Creek

While searching along the cliffs that line the shore of Lake Erie near 18 Mile Creek I found this rather unique fossil. It's the very base of a stem with four "roots" that would have angled off giving it a look like a grappling hook. Based on my experiences this is an anchor for a crinoid called Ancyrocrinus bulbosus.

Looking down the stem towards the base. Note the square shape of the stem which is diagnostic for the species.

To see a more complete specimen of this odd holdfast click here for an image from the database of the Friends of Michigan Museum of Paleontology.

I've found these kinds of fossils in my local Mahantango formation and blogged about it here.

This fossil was found along the shoreline of Lake Erie near the mouth of 18 mile creek. Based on the book "Geology and Paleontology of 18 Mile Creek" by Amadeus Grabau, (pg. 146-147), this species is typically found in the Moscow shale (since promoted to Formation status) which corresponds to the Windom shale. As the Windom shale is present along Lake Erie, and was exposed particularly well in the area I was hunting, I am going to assign that as the former resting place for my fossil.

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